Modified wood and transparent wood composites, as well as systems and methods for forming and using them.

Abstract

In some embodiments, the material comprises a chemically modified continuous wood block infiltrated with a refractive index-matching polymer. The continuous wood block has a first section that is substantially transparent to light and a second section that is translucent or opaque. The first section can have a lower lignin content than the second section. Alternatively, the first section can have a chromophore state that is altered from the chromophore state of the wood in its natural state, and the lignin in the second section can retain the chromophore state of the wood in its natural state. In some embodiments, the material comprises a section of wood that has been chemically modified, whereby the chromophore of the lignin in the wood in its natural state is altered or removed, so that the section retains at least 70% of the lignin in the wood in its natural state. Methods for forming such materials are also disclosed.

Description

[Technical Field]

[0001] [Cross-reference of related applications] This application claims the interests of U.S. Provisional Patent Application No. 63 / 050,484, filed on 10 July 2020, entitled “Patterned, Transparent Wood and Wood Composite Structures and Methods of Making and Using the Same,” and U.S. Provisional Patent Application No. 63 / 134,936, filed on 7 January 2021, both of which are incorporated herein by reference.

[0002] This disclosure generally relates to the processing of naturally occurring wood, and more particularly to the formation and use of modified wood and / or transparent wood composites. [Overview of the project] [Problems that the invention aims to solve]

[0003] Embodiments of the subject matter of this disclosure provide modified wood and transparent wood composites, as well as methods for forming and using them. In some embodiments, a continuous block of wood is subjected to chemical treatment such that the natural portions within it undergo different degrees of lignin removal. For example, the continuous block of wood may be softwood, and its earlywood portions are deligninized while its latewood portions retain a considerable amount of lignin after chemical treatment. Subsequently, the chemically treated wood block is impregnated with a refractive index-matching polymer so that, with respect to wavelengths in the visible light spectrum, the deligninized portions become substantially transparent, while the other portions remain opaque or translucent. The wood composite thus obtained can exhibit a natural pattern defined by the arrangement of transparent earlywood portions and translucent or opaque latewood portions.

[0004] In some embodiments, continuous wood blocks are subjected to UV-assisted photocatalytic oxidation treatment, modifying the lignin within them in situ and resulting in a white wood color. For example, a liquid oxidizing agent such as hydrogen peroxide can be impregnated into continuous wood blocks, followed by UV irradiation to remove the chromophores of the lignin within the wood blocks while retaining the lignin within the wood's microstructure. In some embodiments, applying a liquid oxidizing agent to the surface of a wood block and / or exposing the wood block to UV light can form a pattern that limits the in situ modification to specific parts of the wood block. Subsequently, by impregnating the wood block with a refractive index-matching polymer, the in situ-modified portions become substantially transparent with respect to wavelengths in the visible light spectrum, while the other portions remain opaque or translucent. The wood composite thus obtained can exhibit a predetermined pattern composed of the application of the oxidizing agent and UV light, which is independent of the natural pattern inherent in the wood.

[0005] In a typical embodiment, the material comprises a continuous block of chemically modified wood impregnated with a polymer. The chemically modified wood can retain the cellulosic microstructure of the wood in its natural state. The polymer can have a refractive index substantially matching that of cellulose and can fill voids in the microstructure. The continuous block of wood may have a first section and a second section adjacent to the first section. At least one of the first and second sections is chemically modified such that the lignin properties of the first section differ from those of the second section. The first section may be substantially transparent to light having a wavelength of 600 nm, and the second section may be semi-transparent or opaque to light having a wavelength of 600 nm.

[0006] In another typical embodiment, the material includes a wood section that has been chemically modified so that the chromophore of lignin in the wood in its natural state is altered or removed. This section can retain at least 70% of the lignin in the wood in its natural state. Furthermore, this section can retain the cellulosic microstructure of the wood in its natural state.

[0007] In a typical embodiment, the method includes subjecting a continuous block of wood to a first-time chemical treatment to remove lignin from a first section and a second section within the continuous block of wood while substantially preserving the cellulosic microstructure of the wood. The first section may be adjacent to the second section. The first time may be selected such that at least 90% of the lignin in the wood in the first section is removed and less than 75% (e.g., 65% or less or 50% or less) of the lignin in the second section is removed. Furthermore, the method includes impregnating the continuous block of wood with a polymer to fill the empty spaces within the preserved cellulosic microstructure of the first and second sections. The polymer may have a refractive index substantially matching that of cellulose. After impregnation, the first section may be substantially transparent to light having a wavelength of 600 nm, and the second section may be semi-transparent to light having a wavelength of 600 nm.

[0008] In another typical embodiment, the method includes the steps of applying a first amount of liquid oxidizing agent to the outer surface of a section of a continuous block of wood, and exposing the section of the continuous block of wood to ultraviolet (UV) light during or after the application step. The chromophores of lignin in the section can be chemically oxidized and removed in situ by UV exposure in the presence of the liquid oxidizing agent. After exposure, at least 70% of the lignin in the section before application is retained. Furthermore, after exposure, the section can retain the cellulosic microstructure of the wood before application.

[0009] In another typical embodiment, the method includes the step of photocatalyzing sections of a continuous wood block to chemically modify the natural lignin in the sections in situ while maintaining the bulk aromatic skeleton, and removing the chromophore.

[0010] Any of the innovative technologies of this disclosure may be used in combination or individually. This disclosure is provided to introduce, in a simplified form, a selection of concepts that will be further elaborated in the following detailed description. This disclosure is not intended to identify any important or essential features of the subject matter described in the claims, nor is it intended to be used to limit the scope of the subject matter described in the claims. The aforementioned purposes, features, and advantages of the technologies of this disclosure, as well as other purposes, features, and advantages, will become clearer from the following detailed description, which will be described with reference to the accompanying drawings. [Brief explanation of the drawing]

[0011] Embodiments of the present invention will be described below with reference to the attached drawings. The attached drawings are not necessarily drawn to scale. Some elements may be shown schematically or omitted in order to aid in the illustration and explanation of basic features. In the drawings, similar reference numerals indicate similar elements. [Figure 1A] This is a process flow diagram of a generalized manufacturing method for forming modified wood or transparent wood composite material according to one or more embodiments of the subject matter of the present disclosure. [Figure 1B] This is a simplified process flow diagram illustrating alternative subroutines for forming modified wood or transparent wood composites according to one or more embodiments of the subject matter of this disclosure. [Figure 1C] This is a simplified process flow diagram illustrating alternative subroutines for forming modified wood or transparent wood composites according to one or more embodiments of the subject matter of this disclosure. [Figure 1D]A process flow diagram that simplifies and shows an alternative subroutine for forming modified wood or transparent wood composites according to one or more embodiments of the subject matter of this disclosure. [Figure 2-1] FIG. 2A is a diagram showing fragments cut in the radial, longitudinal, and rotational directions of natural wood that can be used to form modified wood or transparent wood composites according to one or more embodiments of the subject matter of this disclosure. [Figure 2-2] FIG. 2B is a cross-sectional view that simplifies and shows the microstructure of natural wood containing cellulose-based longitudinal cells. FIG. 2C is a photograph of a continuous fragment of natural wood having different sections before treatment. [Figure 2-3] FIG. 2D is a schematic diagram that simplifies and shows different sections of early wood and late wood in natural wood. FIG. 2E is an image obtained by scanning electron microscopy (SEM) of a cross-section in a direction perpendicular to the longitudinal wood growth direction of sections of early wood and late wood in natural wood. [Figure 3] FIG. 3A is a schematic diagram that simplifies and shows different sections of early wood and late wood in a continuous fragment of a wood composite after chemically delignifying and after infiltrating with a polymer according to one or more embodiments of the subject matter of this disclosure. FIG. 3B is an image obtained by SEM of a cross-section in a direction perpendicular to the longitudinal wood growth direction of sections of early wood and late wood in a transparent wood composite after chemically delignifying and after infiltrating with a polymer. FIG. 3C is a photograph of a continuous fragment of a transparent wood composite having a natural pattern after treatment. [Figure 4A] A diagram showing an exemplary batch manufacturing setup and an exemplary continuous or semi-continuous manufacturing setup for forming a transparent wood composite having a natural pattern according to one or more embodiments of the subject matter of this disclosure. [Figure 4B] A diagram showing an exemplary batch manufacturing setup and an exemplary continuous or semi-continuous manufacturing setup for forming a transparent wood composite having a natural pattern according to one or more embodiments of the subject matter of this disclosure. [Figure 4C]This is a perspective view of an exemplary quarter-slice cutting arrangement that can be employed in a manufacturing setup according to one or more embodiments of the subject matter of the present disclosure. [Figure 5A] This is a schematic diagram illustrating the photocatalytic chemical oxidation of lignin in wood and the resulting in situ structural changes, according to one or more embodiments of the subject matter of this disclosure. [Figure 5B] This figure shows an exemplary batch manufacturing method for forming modified wood or transparent wood composites by coating with a pattern of a chemical oxidizing agent (e.g., hydrogen peroxide) according to one or more embodiments of the subject matter of the present disclosure. [Figure 5C] This figure shows an exemplary batch manufacturing method for forming modified wood or transparent wood composites by patterned exposure to ultraviolet light, according to one or more embodiments of the subject matter of the present disclosure. [Figure 5D] This figure shows an exemplary batch manufacturing method for forming patternless modified wood or transparent wood composites according to one or more embodiments of the subject matter of the present disclosure. [Figure 6] This figure shows an exemplary continuous or semi-continuous manufacturing setup for forming modified wood or transparent wood composites according to one or more embodiments of the subject matter of the present disclosure. [Figure 7A] This is a SEM image of the cellulosic microstructure at the boundary between the earlywood and latewood of Douglas fir. [Figure 7B] Figure 7A is a magnified SEM image of the earlywood portion of a natural Douglas fir tree. [Figure 7C] Figure 7A is a magnified SEM image of the latewood portion of a natural Douglas fir tree. [Figure 7D] Figure 7A is an SEM image of a longitudinal section of a Douglas fir tracheid. [Figure 7E] This figure shows the pore size distribution in the earlywood portion of natural Douglas fir. [Figure 7F] This figure shows the pore size distribution in the latewood portion of natural Douglas fir. [Figure 7G] This figure shows the Raman spectra of the cell wall components of the earlywood and latewood portions of natural Douglas fir and a fabricated transparent wood composite with a natural pattern, respectively. [Figure 7H] This figure shows the Raman spectra of cell wall components in a transparent wood composite material with a natural pattern that was fabricated. [Figure 7I] This graph shows the transmittance at 600 nm for the earlywood and latewood portions of a fabricated transparent wood composite with a natural pattern. [Figure 7J] This graph shows the absorption, transmittance, and reflectance spectra of a continuous segment of a fabricated transparent wood composite material with a natural pattern. [Figure 7K] This graph shows the UV blocking properties of continuous fragments of a fabricated transparent wood composite with a natural pattern, based on the deligninization treatment period. [Figure 7L] This graph shows the haze for a series of fragments of a transparent wood composite material with a natural pattern that was fabricated. [Figure 7M] This figure shows an assembly of individual, continuous pieces of transparent wood composite material with natural patterns for forming custom patterns. [Figure 8A] This graph shows the normalized lignin content as a function of treatment time after photocatalytic oxidation treatment to form in situ lignin-modified wood. [Figure 8B] This graph shows the Fourier transform infrared (FTIR) spectra of continuous fragments of natural wood and fabricated in situ lignin-modified wood. [Figure 8C] This graph shows the X-ray diffraction (XRD) spectra of continuous fragments of natural wood and fabricated in situ lignin-modified wood. [Figure 8D] This graph shows the X-ray photoelectron spectroscopy (XPS) spectra of continuous fragments of natural wood and fabricated in situ lignin-modified wood. [Figure 8E]This graph shows the reflectance spectra at different locations of a series of in situ lignin-modified wood fragments. [Figure 8F] These are macro-scale and micro-scale images comparing a continuous fragment of fabricated in situ lignin-modified wood (e.g., photonic wood) with a fragment of fabricated deligninized wood. [Figure 8G] Images of a series of fragments of fabricated in situ lignin-modified wood with a custom pattern. [Figure 8H] Images of a series of fragments of fabricated in situ lignin-modified wood with a custom pattern. [Figure 9A] This graph shows the FTIR spectra of natural wood, continuous segments of fabricated in situ lignin-modified wood, and continuous segments of fabricated transparent wood composites. [Figure 9B] This graph shows the lignin content in natural wood, continuous fragments of fabricated in situ lignin-modified wood, and continuous fragments of fabricated transparent wood composites. [Figure 9C] This is a SEM image of a cross-sectional view of natural wood. [Figure 9D] This is a SEM image of a transverse section of a continuous fragment of in situ lignin-modified wood that was prepared. [Figure 9E] This is a SEM image of a transverse cross-section of a continuous segment of the fabricated transparent wood composite material. [Figure 9F] This graph shows the transmittance spectra of natural wood and transparent wood composite materials, comparing the longitudinal (L) and radial (T) cross-sections. [Figure 9G] This graph shows the absorption spectra of natural wood and transparent wood composite materials, comparing the longitudinal (L) and radial (T) cross-sections. [Figure 9H] This graph shows the haze of continuous fragments of a fabricated transparent wood composite material, formed from longitudinal (L) and radial (T) cuts of natural wood. [Figure 9I] This is an image of a series of fragments of fabricated transparent wood composite material with a custom pattern. [Modes for carrying out the invention]

[0012] [General Precautions] This disclosure describes specific aspects, advantages, and novel features of embodiments of the present invention. The disclosed methods and systems should not be construed as limiting in any way. This disclosure is directed to all novel and non-obvious features and aspects of the various embodiments disclosed, both individually and in various combinations and subcombinations with each other. The methods and systems are not limited to any particular aspect or feature or combination thereof. Furthermore, the disclosed embodiments do not require that one or more specific advantages exist or that a problem is solved. The techniques described in any embodiment or example can be combined with the techniques described in one or more other embodiments or examples. Given the many possible embodiments to which the principles of the disclosed techniques may be applied, it should be noted that the illustrated embodiments are illustrative and do not limit the scope of the disclosed techniques.

[0013] Some operations of the disclosed methods are described in a specific sequential order for convenience, but it should be noted that this order is subject to change unless explicitly stated by certain terminology later. For example, operations described in a specific order may be performed in a different order or simultaneously. Furthermore, for the sake of simplification, various ways of using the disclosed methods in combination with other methods may not be shown in the accompanying drawings. In addition, this disclosure may use terms such as “provide” or “achieve” to describe the disclosed methods. These terms are highly abstract descriptions of the actual operations performed. The actual operations corresponding to these terms may differ depending on the particular embodiment and will be readily identifiable to those skilled in the art.

[0014] It should be noted that, unless otherwise explicitly stated, numerical ranges in this disclosure refer to each discrete point within the range, including the endpoints. Unless otherwise explicitly stated, all numerical values ​​used herein or in the claims, such as the number of components, molecular weight, percentage, temperature, and time, are modified by the term "approximately." Therefore, unless otherwise implicitly or explicitly indicated, or unless the context is appropriately understood to have a clearer structure by those skilled in the art, numerical parameters in this disclosure are approximations, which may depend on the detection limits under the desired properties and / or standard test conditions / methods, as known to those skilled in the art. Where embodiments of the invention are directly and explicitly distinguished from the prior art of this disclosure, numerical values ​​in embodiments are not approximations unless the term "approximately" is used. Where terms such as "substantially," "approximately," "about," or similar terms are explicitly used in combination with a particular value, they are intended to include numerical values ​​approximately 10% of that value, unless otherwise explicitly stated.

[0015] Directions and other relative references may be used to facilitate the explanation of the accompanying drawings and the principles of this disclosure, but are not intended to be limiting. For example, certain terms such as “inside,” “outside,” “top,” “bottom,” “upper,” “lower,” “internal,” “external,” “left,” “right,” “front,” “back,” and “rear” may be used. These terms are used as appropriate to provide some degree of clarity, particularly when dealing with relative relationships with respect to embodiments shown in the figures. However, these terms are not intended to imply absolute relationships, positions, and / or orientations. For example, with respect to an object, the “top” part can simply become the “bottom” part by turning the object upside down. Nevertheless, they remain the same part, and there is no change in the object.

[0016] As used in this disclosure, the term “comprising” means “including,” and the singular definite or indefinite article (a, an, the) also includes multiple elements unless the context otherwise indicates. The term “or” means a single element or a combination of two or more elements from the listed alternative elements unless the context otherwise indicates.

[0017] While alternatives exist for various components, parameters, and operating conditions of this disclosure, these alternatives are not necessarily equivalent or to function in the same way. Furthermore, unless explicitly stated, the alternatives are not listed in a preferred order. Unless explicitly stated, any of the following groups may be replaced or reverted from their respective states.

[0018] Unless otherwise stated, all technical and scientific terms used in this disclosure have the same meaning as those commonly understood by those skilled in the art to which this disclosure pertains. Methods and materials similar to or equivalent to those of this disclosure may be used in the implementation or testing of this disclosure, but suitable methods and materials are described below. These materials, methods and examples are illustrative and are not intended to limit the invention. Other features of the subject matter of this disclosure will become clear from the following detailed description and claims.

[0019] [Overview of Terms] The following explanations of specific terms and abbreviations are provided to facilitate the explanation of various aspects of the subject matter of this disclosure and to assist those skilled in the art in carrying out the subject matter of this disclosure.

[0020] "Continuous fragment": A single continuous piece of wood taken from a single tree and subjected to processing. This is in contrast to a single fragment formed by joining or combining (e.g., laminating) multiple sub-fragments. In some embodiments, the processing creates sections or regions with different lignin properties within the continuous piece of wood.

[0021] "Lignin properties": In some embodiments, lignin properties refer to the naturally occurring or natural lignin content in a wood section. Thus, different lignin properties may refer to the fact that the natural lignin content of a particular wood section is less than that of an adjacent wood section after treatment (e.g., the earlywood region is substantially deligninized, while the adjacent latewood region retains most or at least some of the natural lignin). Alternatively or additionally, in some embodiments, lignin properties refer to the naturally occurring or natural form of lignin in a wood section. Thus, different lignin properties may refer to the fact that the natural lignin in a particular wood section is modified in situ (e.g., by chemical oxidation) to alter or remove the lignin chromophore without removing the lignin, while the adjacent wood section retains the natural form of lignin after treatment.

[0022] "Deligninized": A wood section from which at least 90% of the naturally occurring lignin has been removed. In some embodiments, the lignin content of the deligninized wood section is 3 wt% or less, for example, less than 1 wt%. The lignin content in cellulosic materials before and after deligninization can be evaluated using techniques known in the art. This is described, for example, in Laboratory Analytical Procedure (LAP) TP-510-42618 (version 08-03-2012) in “Determination of Structural Carbohydrates and Lignin in Biomass” published by the National Renewable Energy Laboratory (NREL), which is incorporated herein by reference, and in ASTM E1758-01 (2020) in “Standard Test Method for Determination of Carbohydrates in Biomass by High Performance Liquid Chromatography” published by ASTM International.

[0023] "Longitudinal growth direction": This is the direction in which a plant grows from its roots or stem, and the cellulose nanofibers that form the plant's cell walls are generally aligned in this longitudinal growth direction. In some cases, the longitudinal growth direction may be generally vertical and may correspond to the direction of water transpiration. This is in contrast to the radial growth direction, which extends outward from the central part of the plant and can be generally horizontal.

[0024] "Transparent" means having a transmittance value of at least 80% for a specific wavelength or range of light (i.e., the ratio of the intensity of transmitted light to the intensity of incident light).

[0025] "Translucent": This means having a transmittance value of 36% to 80% for a specific wavelength or range of light wavelengths.

[0026] "Opaque": This means having a transmittance value of less than 36% for a specific wavelength or range of light wavelengths.

[0027] [Introduction] Transparent wood composites with improved mechanical properties can be formed by retaining some or all of the naturally occurring lignin in the wood starting material. Existing transparent wood composites require the removal of most or all (e.g., at least 90%) of the lignin in the wood starting material to achieve high transparency (e.g., over 80% for visible wavelengths). However, such extensive lignin removal can compromise the integrity of the wood's cellulosic microstructure, complicating subsequent manufacturing steps (e.g., polymer infiltration) and potentially reducing the mechanical strength of the resulting composite.

[0028] In some embodiments of the subject matter of this disclosure, a continuous block of wood may be subjected to chemical treatment. This results in varying degrees of lignin removal in the natural portions thereof. For example, the continuous block of wood may be softwood, and its earlywood portion may be deligninized, while its latewood portion may retain a large amount of lignin after chemical treatment. Subsequently, by impregnating the chemically treated wood block with a refractive index matching polymer, the deligninized portions become substantially transparent with respect to wavelengths in the visible light spectrum, while the other portions remain opaque or translucent. The wood composite thus obtained can exhibit a natural pattern composed of transparent earlywood portions and translucent or opaque latewood portions. Furthermore, because the latewood portion retains a large amount of lignin, the overall mechanical strength of the material is improved compared to a completely deligninized wood composite.

[0029] Alternatively or additionally, in some embodiments of the subject matter of this disclosure, a continuous block of wood is subjected to UV-assisted photocatalytic oxidation to modify the lignin therein in situ, resulting in a white color for the wood. For example, a continuous block of wood can be impregnated with a liquid oxidizing agent such as hydrogen peroxide, followed by UV irradiation to remove the chromophore of the lignin in the wood block, while retaining the lignin within the wood's microstructure. In some embodiments, the application of a liquid oxidizing agent to the surface of the wood block and / or exposure of the wood block to UV light can form a pattern that limits the in situ modification to specific sections of the wood block. Subsequently, by impregnating the wood block with a refractive index-matching polymer, the in situ-modified sections become substantially transparent with respect to wavelengths in the visible light spectrum, while other sections remain opaque or translucent. The wood composite thus obtained can exhibit a predetermined pattern composed of the application of the oxidizing agent and UV light, which is independent of the natural pattern inherent in the wood. Because photocatalytic oxidation treatment removes little to no lignin (for example, less than 30% of the lignin in the original wood being removed), the overall mechanical strength of the material is improved compared to wood composites that have been completely deligned.

[0030] Furthermore, transparent wood composites in the prior art require large amounts of chemicals and enormous processing time for deligninization of the wood, which can hinder manufacturability. In contrast, in some embodiments, UV-assisted photocatalytic oxidation treatment can be used to treat the wood by applying a liquid oxidizing agent to the surface, thereby modifying the lignin within it in situ. Therefore, compared to the treatment of transparent wood in the prior art, the processing time and the amount of chemicals used can be reduced. Also, compared to deligninizing agents that generate harmful chlorine gases such as NaClO2, H2O2 produces only water or oxygen as byproducts, so using hydrogen peroxide (H2O2) as a liquid oxidizing agent can provide a more environmentally friendly treatment method.

[0031] In some embodiments, transparent wood composites having a natural pattern (also called aesthetically pleasing wood) are provided. Aesthetically pleasing wood is provided based on spatially selective deligninization and infiltration with refractive index matching polymers (e.g., epoxy resin) to have excellent aesthetic properties (e.g., flawless wood pattern), excellent optical properties (e.g., average transmittance of 80% or less and haze of 93% or less), good UV blocking ability (e.g., transmittance of 20% or less), and low thermal conductivity (0.24 W·m). -1 K -1 It can also have a rapid manufacturing process for wood with a superior aesthetic appearance (e.g., chemical treatment in less than 2 hours) and mechanical robustness (e.g., high longitudinal tensile strength of 91.95 MPa and 2.73 MJ·m). -3 Its toughness allows for mass production while significantly saving time and energy compared to conventional complete deligninization processes. For example, aesthetically pleasing wood can be used in energy-efficient building applications such as glass ceilings, rooftops, transparent decorative elements, and interior panels.

[0032] In some embodiments, modified wood (also called in situ lignin-modified wood, lignin-modified wood, or photonic wood) is provided. Lignin in natural wood can be modified in situ using a rapid and scalable process, particularly by photocatalytic oxidation of the natural lignin in the wood using a liquid oxidizing agent (e.g., hydrogen peroxide) and UV light (e.g., UVA solar radiation or artificial lighting). The photocatalytic oxidation reaction selectively removes the chromophore of lignin while preserving the aromatic skeleton of lignin, thereby altering the optical properties of the wood. In the photonic wood thus obtained, less than 80% of the original lignin content is retained, so the photonic wood can continue to function as a strong binder and waterproofing agent. As a result, compared to deligninized wood, photonic wood exhibits significantly improved mechanical strength in humid environments (e.g., 20 times greater tensile strength and 12 times greater compressive strength), increased scalability (e.g., samples under 2 meters), and significantly reduced processing time (e.g., 1 to 6.5 hours compared to 4 to 14 hours). Furthermore, the structure of in-situ lignin-modified wood can have patterns due to a photocatalytic oxidation process, particularly the selective application of a liquid oxidizing agent or UV irradiation to the wood surface. The production of photonic wood using this photocatalysis enables the mass production of sustainable, bio-derived functional materials for various applications, including energy-efficient buildings, lighting management, and fluid, ion, electronic, and optical devices.

[0033] In some embodiments, transparent wood composites (also called transparent in situ lignin-modified wood composites, transparent wood composites with artificial patterns, or simply transparent wood) are provided. The lignin in natural wood can be modified by UV-assisted photocatalytic oxidation, similar to photonic wood. This preserves most of the natural lignin that acts as a binder, providing a robust wood skeleton for polymer permeation, while significantly reducing chemical and energy consumption, as well as processing time. After polymer permeation, the resulting transparent wood (e.g., less than 1 mm thick) can exhibit high transmittance (e.g., over 90%), high haze (e.g., over 60%), and excellent light-guiding effects for visible light wavelengths. Also, similar to photonic wood, patterns can be directly formed on the wood surface by selectively applying a liquid oxidizing agent (e.g., brushing or printing) or UV irradiation (e.g., masking or laser irradiation). Since modified lignin binds to highly oriented cellulose fibrils, lignin-modified wood has substantially higher tensile strength (e.g., 20.6 MPa) than deligninized wood (e.g., tensile strength of 0.4 MPa).

[0034] [Examples of the method] Figure 1A shows an exemplary method 100 for forming modified wood or transparent wood composites. The method 100 can begin with a process block 102, where a continuous piece 101 of natural wood is prepared. For example, the preparation of the process block 102 may include cutting, removing, or separating the wood piece from a parent tree. In some embodiments, cutting can form the natural wood into a substantially flat planar structure, where the orientation of the cellulose fibers extends either parallel to the plane of the structure (e.g., longitudinal or rotational cross-section) or perpendicular to the plane of the structure (e.g., radial cross-section). Optionally, in some embodiments, the preparation may include pretreatment of the natural wood piece. For example, this may include washing to remove undesirable material or contamination in preparation for subsequent processing, shaping the natural cellulosic material into a specific form (e.g., slicing into strips) in preparation for subsequent processing, or any combination thereof. In some embodiments, the continuous piece 101 of natural wood may be softwood, which has clearly defined naturally occurring sections with different properties, such as earlywood (EW) regions 103 and adjacent latewood (LW) regions 105. Alternatively, in some embodiments, the continuous piece 101 of natural wood may be hardwood or softwood that does not have clearly defined naturally occurring sections.

[0035] In process block 104, one or more chemical treatments are applied to a continuous piece of natural wood to modify the lignin properties of at least one section of the wood piece. In some embodiments, the modification of lignin properties results in at least one section having different lignin properties from adjacent sections. For example, in some embodiments, the lignin properties are the lignin content of a section of the continuous piece of treated wood 107, and the chemical treatment can be made such that the lignin content of one wood section 109 (e.g., the original EW region 103) is less than that of an adjacent wood section 111 (e.g., the original LW region 105), as will be described later with reference to Figure 1B. Alternatively, in some embodiments, the lignin properties are the presence of a chromophore, and the chemical treatment removes the chromophore in one wood section 109 while retaining the chromophore in the adjacent wood section 111, as will be described later with reference to Figures 1C-1D. Alternatively, in some embodiments, modification of the lignin properties is used to form a continuous fragment such that it has lignin properties (e.g., lignin content or presence of a chromophore). Next, the method 100 can proceed to the decision block 106. Here, it is determined whether a transparent composite is desirable. For example, if it is determined that using a transparent composite as photonic wood is undesirable, the method 100 can proceed from the decision block 106 to the process block 110. If it is determined that a transparent composite is desirable, the method 100 can proceed from the decision block 106 to the process block 108. Here, a refractive index matching polymer is impregnated into a continuous piece of modified wood.

[0036] In some embodiments, the step of impregnating process block 108 with the polymer can be achieved, for example, by immersing the modified wood in a container of liquid polymer or polymer precursor and applying a vacuum to the chamber containing the container, or by one or more vacuum-assisted impregnation sessions, as described in International Publication 2017 / 136714, filed on 3 February 2017, which is incorporated by reference herein. The polymer may be any polymer having a refractive index substantially matching that of cellulose (e.g., refractive index ≤ 1.47) and capable of penetrating the microstructure of the wood. For example, the impregnated refractive index-matching polymer may include any type of thermosetting polymer (e.g., epoxy resin), thermoplastic polymer (e.g., acrylic), cellulose derivative (e.g., cellulose acetate), and / or functional refractive index-matching materials (e.g., liquid crystal or piezoelectric materials). Non-limiting examples of polymers that can be impregnated into modified wood are those described in International Publication 2017 / 136714, which is incorporated by reference herein. In some embodiments, the polymer may be an epoxy resin (e.g., AeroMarine300 / 21 epoxy).

[0037] In some embodiments, the process block 110 may include a step of drying or polymerizing the impregnated precursor. In some embodiments, the polymer-impregnated modified wood is pressed during drying or polymerization. For example, if a first section 109 is deligninized in process block 104 and a second section 111 retains lignin, the different mechanical strengths of these sections may lead to warping as the polymer dries or polymerizes in these sections. Therefore, warping can be prevented or at least reduced by applying nominal pressure during drying or polymerization (e.g., without changing the thickness of a continuous piece by more than 10%).

[0038] Thus, by impregnating the wood section with polymer through the process block 110, part or all of the wood section can be made substantially transparent. For example, if the wood section 109 is substantially deligninized or its chromophore removed through chemical treatment in the process block 104, the impregnating polymer can make section 109 a substantially transparent section 115. On the other hand, if the wood section 111 retains lignin and its chromophore after chemical treatment in the process block, section 111 remains a translucent or opaque section 117 after polymer impregnation. Alternatively, in some embodiments, if the entire continuous fragment 107 is formed to have modified lignin properties, the entire fragment 113 becomes transparent after polymer impregnation.

[0039] If polymer impregnation is undesirable in process block 108, or if polymer impregnation is undesirable in determination block 106, the method 100 may proceed to process block 110. Here, the modified wood or transparent wood composite is used for a specific application or adapted for use for a specific application. For example, process block 110 may include steps of machining, cutting, or shaping continuous pieces into a specific form. The use of process block 110 may include using continuous pieces of modified wood or transparent wood composite by itself, or assembling them with non-wood materials (e.g., metal, metal alloy, plastic, ceramic, composite, etc.) to form a heterogeneous composite structure. In some embodiments, after polymer impregnation in process block 108, continuous pieces of transparent wood composite can be used as part of a building (e.g., a window or skylight). Alternatively, in some embodiments, if a transparent composite is undesirable in determination block 106, continuous pieces of modified wood can be used as an insulating structure or a visible light reflector. Other applications not specifically described above may also be applied to modified wood and transparent wood composite structures produced according to the disclosed technology. In fact, those skilled in the art will readily understand that the modified wood and transparent wood composite structures disclosed herein can be adapted for other uses based on the teachings of this disclosure.

[0040] Although blocks 102-110 of Method 100 have been described as being performed once, in some embodiments, multiple repetitions of a particular process block may be employed before proceeding to the next decision block or process block. Furthermore, although blocks 102-110 of Method 100 have been illustrated and described individually, in some embodiments, process blocks may be combined and performed together (simultaneously or sequentially). Also, while Figure 1A shows a specific order of blocks 102-110, the order is not limited to this in embodiments of the subject matter of this disclosure. In fact, in certain embodiments, blocks may be performed in a different order than shown in the figure, or simultaneously with other blocks.

[0041] Figure 1B shows a first exemplary subroutine 104a that may be used for the chemical treatment of process block 104 of method 100 in Figure 1A. For example, subroutine 104a may be used to form a transparent wood composite with a natural pattern based on the selective deligninization of naturally occurring EW and LW sections in softwood (e.g., pine, cedar, spruce, larch, or fir). Subroutine 104a can be started in process block 112, where a continuous piece of natural wood is immersed in one or more chemical solutions to remove lignin from the wood. The physical properties of the EW section (e.g., lower density, larger lumen, thinner cell wall) compared to the LW section (e.g., higher density, smaller lumen, thicker cell wall) allow the chemical solution to penetrate and react more easily with the EW section. This allows lignin to be removed more quickly from the EW section than from the LW section. By appropriately timing the chemical treatment of process block 112, the EW and LW sections can be treated to have different lignin content. In particular, by ending the chemical treatment of the EW section after or immediately after deligninization (for example, by removing continuous fragments from the solution), the LW section can retain a large amount of lignin.

[0042] In some embodiments, the chemical treatment of process block 112 may be carried out under vacuum. This facilitates complete penetration of the treatment solution into the cell walls and lumens of the continuous wood fragments. Alternatively, in some embodiments, the chemical treatment of process block 112 may be carried out under ambient pressure or under boosted pressure (e.g., 6 bar to 8 bar). In some embodiments, the chemical treatment of process block 112 may be carried out at any temperature between ambient temperature (e.g., below 23°C) and a high temperature at which the chemical solution boils (e.g., 70°C to 160°C). In some embodiments, the chemical solution is not stirred to avoid destruction of the cellulosic microstructure of the wood. In some embodiments, the chemical solution may contain sodium chlorite (NaClO2) alone or in combination with other chemicals (e.g., acetic acid). For example, in some embodiments, the chemical solution contains a boiling solution of NaClO2.

[0043] In some embodiments, the immersion time may be less than 5 hours, for example, 2 hours or less. The immersion time in the chemical solution may be a function of the amount of lignin removed, the size of the fragments, the density of the EW section, the temperature of the solution, the pressure of the process, and / or stirring. For example, a smaller amount of lignin removed, a smaller fragment size, a lower density of the EW section, a higher solution temperature, a higher processing pressure, and stirring may be associated with a shorter immersion time, while a larger amount of lignin removed, a larger fragment size, a higher density of the EW section, a lower solution temperature, a lower processing pressure, and no stirring may be associated with a longer immersion time.

[0044] In decision block 114, it is determined whether to continue processing in process block 112. Processing with a chemical solution may be continued (or repeated with subsequent solutions) until the lignin content in the EW section is reduced to a desired level, for example, until the desired light transmittance is obtained after penetration with a refractive index matching polymer in process block 108. In some embodiments, processing in process block 112 is continued until the lignin content in the EW section is reduced by at least 90% (for example, until less than 10% of the original lignin in the EW section is retained). This can correspond to at least 80% light transmittance for one or more wavelengths in the visible light spectrum (e.g., 600 nm). For example, after processing in process block 112, the EW section may have a lignin content of 3 wt% or less, for example, 1 wt% or less. In some embodiments, processing with process block 112 may be effective in reducing the lignin content in the LW section by 75% or less (e.g., retaining more than 25% of the original lignin in the LW section), for example, 65% or less, or even further by 50% or less. This can correspond to a light transmittance of less than 70% for one or more wavelengths in the visible light spectrum (e.g., 600 nm). For example, after processing with process block 112, the LW section may have a lignin content of 7.5 wt% or more, for example, 12.5 wt% or more.

[0045] Once sufficient lignin has been removed from the EW section, subroutine 104a can proceed from decision block 114 to process block 116. Here, the continuous pieces of modified wood are removed from the chemical solution in preparation for polymer infiltration in process block 108. In some embodiments, process block 116 may further include an optional rinsing step after the chemical treatment to remove any residual chemicals or particulate matter resulting from the delignin process. For example, the continuous wood blocks of modified wood may be partially or completely immersed in one or more rinsing solutions. The rinsing solutions may be, but are not limited to, deionized (DI) water, alcohol (ethanol, methanol, isopropanol, etc.), or any combination thereof. For example, the rinsing solution may be formed from water and ethanol. In some embodiments, rinsing may be repeated multiple times (e.g., at least three times) using a fresh mixed rinsing solution each time. In some embodiments, after rinsing, the continuous pieces may be stored in alcohol (e.g., ethanol). In some embodiments, after storage, the continuous fragments may be immersed in another solvent (such as toluene) to replace the alcohol therein before polymer infiltration in process block 108.

[0046] Although blocks 112-116 of subroutine 104a have been described as being executed once, in some embodiments, multiple repetitions of a particular process block may be employed before proceeding to the next decision block or process block. Furthermore, although blocks 112-116 of subroutine 104a have been illustrated and described individually, in some embodiments, process blocks may be executed together (simultaneously or sequentially) in combination. Also, while Figure 1B shows a specific order of blocks 112-116, the order is not limited to this in embodiments of the subject matter of this disclosure. In fact, in certain embodiments, blocks may be executed in a different order than shown in the figure, or simultaneously with other blocks.

[0047] Figure 1C shows a second exemplary subroutine 104b that may be used for the chemical treatment of process block 104 of method 100 in Figure 1A. For example, subroutine 104b may be used to form continuous pieces of in situ lignin-modified wood having a pattern or transparent wood composite having a pattern. Subroutine 104b can be started in any process block 118, where a predetermined pattern contour is formed on the upper exposed surface of the continuous piece of wood so as to define adjacent first and second sections in the wood. For example, the contour may be formed using a hydrophobic material such as petrolatum. This contour may be effective in preventing a liquid oxidizing agent (e.g., hydrogen peroxide) from flowing from the first section to the second section (or vice versa) when applied to the surface. However, in some embodiments, the contour may be omitted if, for example, the liquid oxidizing agent is applied in a way that avoids or at least reduces lateral spreading to adjacent sections. In some embodiments, a given pattern can define a plurality of first sections separated from each other by one or more intervening second sections.

[0048] Subroutine 104b can then proceed to any process block 120, where a first amount of alkali in solution is applied to the upper exposed surface portion of the continuous piece corresponding to the first section. For example, the alkali may be sodium hydroxide (NaOH), potassium hydroxide (KOH), ammonium hydroxide (NH4OH), calcium hydroxide (Ca(OH)2), or any combination thereof. In some embodiments, the concentration of alkali in solution is at least 10 wt%. Application can be by brushing, spraying, rolling, printing, or any other controlled surface application technique. In some embodiments, the first amount can be much less than the corresponding amount of liquid oxidizer applied in the subsequent process block 122. For example, the first amount may be 20% or less of the amount of liquid oxidizer. In some embodiments, the first amount is in the range of 1 ml to 3 ml (inclusive). Including a small amount of alkali can promote the decomposition of the liquid oxidizer (e.g., H2O2) without causing substantial lignin removal from the wood. However, in some embodiments, the application of alkali to continuous pieces of wood can be omitted.

[0049] Next, subroutine 104b can proceed to process block 122, where a second amount of liquid oxidizer is applied to the upper exposed surface portion of the contiguous piece corresponding to the first section. For example, the liquid oxidizer may be H2O2 with a concentration of at least 30 wt%. In some embodiments, the liquid oxidizer may be applied to the surface portion of the first section without being applied to the surface portion of the second section. The application of the oxidizer defines the pattern. The application can be done by brushing, spraying, rolling, printing, or any other controlled surface coating technique. In some embodiments, a portion of the second amount may be applied to the upper exposed surface portion, and the remainder of the second amount may be applied simultaneously or subsequently to the lower exposed surface portion on the opposite side of the contiguous piece.

[0050] In some embodiments, the second amount may be determined based on the surface area and / or thickness of the wood section to which the liquid oxidizing agent is applied. For example, if the thickness of a continuous piece (e.g., in the direction perpendicular to the upper exposed surface) is 0.6 mm or less, the second amount of liquid oxidizing agent to be applied may be at least 800 ml per square meter of surface area. If the thickness of a continuous piece is 0.8 mm or less, the second amount of liquid oxidizing agent to be applied may be at least 1200 ml per square meter of surface area. If the thickness of a continuous piece is 1 mm or less, the second amount of liquid oxidizing agent to be applied may be at least 2400 ml per square meter of surface area. Alternatively, the second amount of liquid oxidizing agent to be applied may be 0.1 mm thick and at least 125 ml per square meter of surface area. In some embodiments, the second amount of liquid oxidizing agent to be applied may be determined based on the volume of the wood section to which the liquid oxidizing agent is applied. For example, the second quantity can be at least equal to the volume of the wood section, or in the range of 1 to 5 times the volume of the wood section (including both ends). For example, the second quantity could be 10 ml to 20 ml (including both ends).

[0051] Next, subroutine 104b can proceed to process block 124, where the continuous wood blocks are subjected to UV irradiation from a natural light source (e.g., solar radiation with a UV index of 5 or higher) or an artificial light source (e.g., 20W in the UVA band). In some embodiments, the entire upper surface may be exposed to UV irradiation for a time sufficient to modify the lignin in the first section in situ via photocatalytic oxidation, in particular, for a time sufficient to remove the chromophore from the lignin. The exposure in process block 124 may be continued via determination block 126 until the photocatalytic oxidation reaction in the first section progresses to a completed state in which the first section becomes completely white. In some embodiments, the exposure time may be less than 2 hours, for example, 1 to 2 hours.

[0052] After exposure, the continuous wood block can retain at least 80% of the original lignin in the whitened first section (e.g., the lignin content is reduced to 20% or less). Furthermore, since the adjacent second section is not subjected to photocatalytic oxidation (e.g., because it is not coated with an oxidizing agent), substantially all of its original lignin is retained. Therefore, the second section can have a slightly higher lignin content than the first section. For example, after treatment in process block 124, both the first and second sections can have a lignin content of 15 wt% or more.

[0053] Although blocks 118-126 of subroutine 104b have been described as being performed once, in some embodiments, multiple repetitions of a particular process block may be employed before proceeding to the next decision block or process block. For example, the application of the liquid oxidizing agent in process block 122 can be achieved by multiple application amounts (e.g., by brushing the same surface area two or more times (e.g., three to ten or more times) to cumulatively apply the desired second amount). Also, although blocks 118-126 of subroutine 104b have been illustrated and described individually, in some embodiments, process blocks may be combined and performed together (simultaneously or sequentially). For example, the application of a first amount of alkali in solution in process block 120 may be performed in combination with the application of a second amount of liquid oxidizing agent in process block 122. Furthermore, although Figure 1C shows a specific order of blocks 118-126, the order is not limited to this in embodiments of the subject matter of this disclosure. In fact, in certain embodiments, blocks may be performed in a different order than shown in the figure, or simultaneously with other blocks.

[0054] Figure 1D shows a third exemplary subroutine 104c that may be used for the chemical treatment of process block 104 of method 100 in Figure 1A. For example, subroutine 104c may be used to form continuous pieces of in situ lignin-modified wood having a pattern or transparent wood composite having a pattern. Subroutine 104c can be started in any process block 128, where a first amount of alkali in solution is applied to some or all of the upper exposed surface of the continuous piece. Other details in process block 128 may be the same as those of process block 120 described above for subroutine 104b. Subroutine 104c can then proceed to process block 130, where a second amount of liquid oxidizing agent (e.g., H2O2) is applied to some or all of the upper exposed surface of the continuous piece. Other details in process block 130 may be the same as those of process block 122 described above for subroutine 104c. Alternatively, in some embodiments, coating in process block 130 may be carried out not by surface coating of the oxidizing agent, but by immersion of continuous pieces of wood in an oxidizing agent bath. The continuous pieces of wood may be removed from the bath after sufficient penetration of the oxidizing agent and before exposure to UV in process block 132.

[0055] Next, subroutine 104c can proceed to process block 132, where a series of wood blocks are subjected to UV irradiation from a natural or artificial light source. In some embodiments, UV irradiation may be applied to the upper exposed surface portion of the first section without being applied to the upper exposed surface portion of the second section. Exposure to UV defines a pattern. For example, UV irradiation from a light source may pass through a photomask to shield the second section from exposure. Alternatively or additionally, the UV light source may be a UV laser or laser diode (e.g., an Nd:YAG laser) configured and controlled to sequentially irradiate the upper exposed surface portions corresponding only to the first section. In some embodiments, exposure of the upper surface portion of the first section to UV may continue for a sufficient time to modify the lignin in the first section in situ via photocatalytic oxidation, in particular, for a sufficient time to remove the chromophore from the lignin. Exposure in process block 132 may continue via determination block 134 until the photocatalytic oxidation reaction in the first section progresses to a completed state in which the first section becomes completely white. In some embodiments, the exposure time may be 2 hours or less, for example, 1 to 2 hours.

[0056] After exposure, the continuous wood block can retain at least 70% of the original lignin in the whitened first section (e.g., the lignin content is reduced to 30%). Furthermore, since the adjacent second section has not been subjected to photocatalytic oxidation (e.g., UV irradiation has not been performed on it), substantially all of its original lignin is retained. Therefore, the second section can have a slightly higher lignin content than the first section. For example, after treatment in process block 132, both the first and second sections can have a lignin content of 15 wt% or more.

[0057] Although blocks 128-134 of subroutine 104c have been described as being performed once, in some embodiments, multiple repetitions of a particular process block may be employed before proceeding to the next decision block or process block. For example, the application of the liquid oxidizing agent in process block 130 can be effective through multiple application amounts (e.g., by brushing the same surface area two or more times (e.g., three to ten or more times) to cumulatively apply the desired second amount). Also, although blocks 128-134 of subroutine 104c have been illustrated and described individually, in some embodiments, process blocks may be combined and performed together (simultaneously or sequentially). For example, the application of a first amount of alkali in solution in process block 128 may be performed in combination with the application of a second amount of liquid oxidizing agent in process block 130. Furthermore, although Figure 1D shows a specific order of blocks 128-132, the order is not limited to this in embodiments of the subject matter of this disclosure. In fact, in certain embodiments, blocks may be performed in a different order than shown in the figure, or simultaneously with other blocks.

[0058] [Examples of transparent wood composite materials with natural patterns] The cell walls of natural wood consist mainly of cellulose (40 wt% to 50 wt%), hemicellulose (20 wt% to 30 wt%), and lignin (20 wt% to 30 wt% in hardwoods, and 25 wt% to 35 wt% in softwoods), and these three components intertwine to form a strong and rigid wall structure. As shown in the exemplary section 212 of Figure 2B, natural hardwood has a unique three-dimensional porous structure and has multiple channels or lumens formed by longitudinal cells, including vessels 214 that extend in the wood growth direction 210 (for example, with a maximum cross-sectional dimension in a plane perpendicular to its length, i.e., a diameter of 40 μm to 80 μm (including both ends)) and fibers 216 (for example, with a maximum cross-sectional dimension in a plane perpendicular to its length, i.e., a diameter of 10 μm to 30 μm (including both ends)). In contrast to hardwoods, softwoods rely on ray tissue and tracheids 215 extending along the wood growth direction 210 to transport water. The tracheids can have a maximum cross-sectional dimension, i.e., diameter, which can vary depending on the location of the tracheids within the wood cross-section.

[0059] Softwoods are woods composed of gymnosperms such as pine (Eastern white pine, lodgepole pine, Parana pine, Scott pine, Southern yellow pine, etc.), cedar (Surian, etc.), spruce (European spruce, Sitka spruce, etc.), larch, and fir (Douglas fir, etc.). Natural softwoods exhibit an excellent pattern of unique aesthetic appearance, known as annual rings, which have an alternating structure on macroscopic and microscopic scales. As shown in Figures 2C and 2D, from a macroscopic perspective, the annual rings are due to the alternating formation of spring EW218 and summer LW220. Each EW region 218 is generally wider, weaker, more porous, and lighter in color than the LW region 220. In terms of microstructure, cells within the EW region 218 have a relatively large lumen diameter 215a and a thin cell wall compared to the lumen 215b within the LW region 220, as shown in Figure 2E.

[0060] Fragments of natural wood can be cut in any direction relative to its longitudinal growth direction 210. Since the tracheids are naturally aligned in the growth direction, the cutting direction determines the orientation of the cellular lumen in the final structure. This orientation can affect the optical or mechanical properties of the final transparent wood composite. For example, in some embodiments, fragments of natural wood may be cut perpendicular or longitudinally (e.g., parallel to the longitudinal wood growth direction 210) from the trunk 202 of the tree 200 so that the longitudinal cell lumen is oriented substantially parallel to the principal surface (e.g., maximum surface area) of the longitudinally cut wood fragment 206. Alternatively, in some embodiments, fragments of natural wood may be cut horizontally or radially (e.g., perpendicular to the longitudinal wood growth direction 210, also called transverse cutting) so that the longitudinal cell lumen is oriented substantially perpendicular to the principal surface of the radially cut wood fragment 204. Alternatively, in some embodiments, a piece of natural wood may be cut in a rotational direction (e.g., perpendicular to the longitudinal wood growth direction 210 and along the circumferential direction of the trunk 202) such that the lumen of the longitudinal cells is oriented substantially parallel to the principal surface of the rotationally cut piece of wood 208. In some embodiments, a piece of natural wood may be cut in any other direction among the longitudinal, radial, and rotational cuts. For any cutting direction, the thickness of the piece of natural wood may be measured perpendicular to the principal surface and may be 10 mm or less.

[0061] Using the naturally occurring pattern of alternating EW regions 218 and LW regions 220 shown in Figures 2C to 2E, a transparent wood composite can be formed that inherits the naturally occurring pattern and possesses desirable optical and mechanical properties. For example, softwood can be subjected to spatially selective deligninization and subsequent polymer infiltration, as described above with respect to Figures 1A and 1B. After spatially selective deligninization, the EW regions 218 can become almost completely white due to the scattering of light and removal of light absorbers (e.g., lignin and some extracts), while the LW regions 220 partially retain lignin. Subsequently, penetration using refractive index-matching polymers yielded a continuous fragment 304 having adjacent sections with different optical properties, as shown in Figures 3A-3C, specifically section 318 based on the original EW region 218 which is substantially transparent (e.g., at least 80% transmittance for light with a wavelength of 600 nm), and section 320 based on the original LW region 220 which is substantially translucent or opaque (e.g., less than 70% transmittance for light with a wavelength of 600 nm). In addition to the different light transmittance values ​​(based on deligninization of the EW region 218 versus partial removal of only lignin in the LW region 220), the retention of lignin within the LW region 220 can impart enhanced mechanical strength and favorable UV absorption properties to the transparent wood composite with a natural pattern.

[0062] In some embodiments, transparent wood composites having a natural pattern can be produced using a batch manufacturing process. For example, Figure 4A shows an exemplary manufacturing setup 400 employing a batch operation. In a first step 402, a continuous piece 408 of softwood having clearly defined EW sections 410 and LW sections 412 can be immersed in a deligninized solution 406 (e.g., NaClO2) in a fluid chamber 404 for a predetermined period or until the EW sections 410 whiten. The continuous modified piece 420 thus obtained includes substantially deligninized EW sections 422 alternating with LW sections 424 that retain non-white lignin. In a subsequent second step 414, the continuous modified piece 420 is immersed in a liquid polymer or polymer precursor 418 in a chamber 416 (e.g., a vacuum chamber) to allow the modified EW sections 422 and LW sections 424 to penetrate into the cellulosic microstructure. This forms a transparent wood composite 432 having fully transparent sections 434 alternating with translucent or opaque sections 436.

[0063] In some embodiments, a continuous fragment is removed from the fluid chamber 404 in the first stage 402 and inserted into the chamber 416 in the second stage 414. Alternatively, in some embodiments, the fluid chambers 404 and 416 are identical, and the transition from the first stage 402 to the second stage 414 is brought about by replacing the delignin solution 406 with a liquid polymer or precursor 418. It should be noted that, although not specifically described above, the batch production setup 400 may include one or more rinsing steps (not shown).

[0064] In some embodiments, the batch manufacturing setup may optionally include a drying or polymerization step 426 employing a press setup (e.g., a hydraulic press). For example, the press setup may have an upper mounting plate 430 and a lower mounting plate 428, where one or both mounting plates can move toward the other to apply pressure to the wood composite 432 held between them. For example, the press setup may apply nominal pressure to maintain the thickness and / or flatness of the upper and lower surfaces of the composite 432 as the polymer therein hardens. In some embodiments, the pressing step 426 may include heating of the composite 432 while it is being pressed, for example by heating one or both of the mounting plates 428 and 430.

[0065] In some embodiments, transparent wood composites having a natural pattern may be produced using a semi-continuous manufacturing process. For example, Figure 4B shows an exemplary manufacturing setup 450 employing a semi-continuous operation. The natural softwood 452 may be in the form of a log or a cylindrical rod, its cavity extending along a direction 454. The natural wood 452 can be repeatedly cut by a longitudinal blade 456, for example using the quarto approach in Figure 4C, to produce long slices 458 having both EW (exhaust) regions 482 and LW (lung) regions 484. The sliced ​​layers 458 may be transported to a delignin station 460 for the next step in the manufacturing process, for example, as described above with respect to process block 112 of subroutine 104a, by immersing the wood 458 in a chemical solution 462 to deligninize the EW sections and partially remove lignin from the LW sections. In some embodiments, the size of station 460 and the conveying speed of the wood layer 458 through station 460 may correspond to a desired immersion time for chemical treatment. Thus, the time from when a portion of the layer 458 enters station 460 until it exits rinsing station 464 will correspond to the immersion time for a desired amount of lignin removal from the EW section.

[0066] After the delignin station 460, the modified slice layer 458 may continue to be transported to the next station, for example, a rinsing station 464. The rinsing station may include one or more solvents 466 (water, alcohol, etc.) and one or more agitators configured to remove any remaining delignin chemicals 462 in the modified layer. Although only a single rinsing station is shown in Figure 4B, multiple stations may be provided to allow for solvent exchange before polymer infiltration.

[0067] After rinsing station 464, the modified slice layer 458 may continue to be transported to the next station, such as polymer station 468, which contains a liquid polymer or polymer precursor 472 in a chamber (e.g., a vacuum chamber). The penetration of the modified EW and LW sections into the cellulosic microstructure forms a transparent wood composite 480 having completely transparent sections alternating with translucent or opaque sections.

[0068] In some embodiments, the manufacturing setup 450 may optionally include a drying or polymerization station 474 employing complementary rollers 476 and 478. In some embodiments, the upper roller 476 and lower roller 478 are spaced apart from each other at a fixed distance substantially equal to or slightly less than the thickness of the composite wood 480. This allows for the application of a nominal pressing force that suppresses warping during drying or polymerization. In some embodiments, one or both of the rollers 476 and 478 may be heated to raise the temperature of the composite 480 above room temperature. This promotes, for example, the solidification or polymerization of the polymer. Alternatively or additionally, the rollers 476 and 478 may not be heated, but a separate heating mechanism may be provided, and the environment including or following the station 474 may be heated.

[0069] [Examples of In Situ Lignin Modification] As shown in Figure 5A, in situ lignin modification in hardwoods or softwoods is achieved by a photocatalytic oxidation mechanism that occurs when the naturally occurring form of lignin 503 is simultaneously exposed 501 to both an oxidizing agent 505 (e.g., hydrogen peroxide) and UV radiation 507. Without being bound by any particular theory, UV light 507 acts as a photocatalyst, cleaving conjugated double bonds to produce a chromophore (Lig·) from lignin and promoting the decomposition of the oxygen / peroxy group (O· / HOO·) of H2O2. The photoexcited Lig· and O· / HOO· participate in the photocatalytic oxidation reaction to form unconjugated carboxyl groups 509, leading to the decolorization of the material and the formation of modified wood. In addition, a small reaction occurs in which the aromatic ring structure in a very small amount of lignin undergoes a ring-opening reaction, forming soluble low-molecular-weight H2O2. This reaction may slightly reduce the lignin content of the treated wood (e.g., to 20% or less). Since this reaction requires both UV light 507 and an oxidizing agent 505, both can be applied to sections where modification is desired, and either UV light or the oxidizing agent can be applied to sections where modification is undesirable, rather than both, to obtain the desired wood pattern. In some embodiments, the in situ lignin-modified wood is used as is without further processing. Alternatively, in some embodiments, the modified wood is further processed by impregnating it with a polymer to form a transparent wood composite.

[0070] In some embodiments, patterned transparent wood composites can be manufactured using a batch manufacturing process. For example, Figure 5B shows the operation of an exemplary batch manufacturing method. In the initial stage 500, a continuous piece 502 of wood of any cut (e.g., R-cut, L-cut, T-cut, etc.) and any type of wood (e.g., softwood or hardwood) is provided. The continuous piece 502 may have an upper surface 504 to which an oxidizing agent is applied in the second stage 506. In some embodiments, a predetermined pattern contour 508 is first formed on the upper surface 504 to demarcate the first section 510 from the second section 512. For example, the pattern contour 508 may be formed using a hydrophobic material such as petrolatum. Alternatively, in some embodiments, no physical contour 508 is provided. Instead, a physical application of an oxidizing agent (and optionally an alkali before or concurrently with the oxidizing agent) to a specific portion of the upper surface 504 can define the predetermined pattern 508. For example, a controlled amount of oxidizing agent can be applied to the first section 510 by painting, coating, printing, or other means using a brush 514, without applying it to the second section 512. Other mechanisms for applying a controlled amount to the surface are also possible according to one or more intended embodiments.

[0071] In the third step 516, the entire upper surface 504 may be exposed to UV irradiation 518 from a natural or artificial light source. Alternatively, in some embodiments, only the first section 510 may be exposed to UV irradiation 518 (for example, in a similar manner to the UV exposure step 540 in Figure 5C). In either case, the combination of oxidizing agent and UV irradiation in the first section 510 rather than the second section 512 causes photocatalytic oxidation only in the first section 510. The modified wood 522 (e.g., photonic wood) thus obtained in step 520 has a first section 524 that is lignin-modified in situ and substantially whitened, and a second section 526 that retains its natural lignin and is substantially non-white (e.g., the color of natural wood). In some embodiments, the modified wood 522 in step 520 can be used as is, for example, as a thermal insulator or optical reflector.

[0072] Alternatively, in some embodiments, the modified wood 522 is subjected to further processing in the final stage 528. For example, the wood 522 can be impregnated with a refractive index-matching polymer to form a patterned transparent wood composite 530 having a transparent first section 532 and adjacent translucent or opaque second section 534. For example, as described above with respect to Figure 1A, the microstructure of the modified wood 522 can be impregnated with a liquid polymer or polymer precursor by immersing it in the microstructure and applying a vacuum for a certain period of time.

[0073] Figure 5C shows another exemplary batch operation for producing a transparent wood composite with a pattern. In the second step 536, an oxidizing agent 538 may be applied to the entire upper surface 504 of a continuous piece of wood 502. In some embodiments, a controlled amount of the oxidizing agent can be applied to the entire upper surface 504 using a brush or other mechanism, for example, in the same manner as described above for the second step 506 in Figure 5B. Alternatively, the application of the oxidizing agent may be carried out by immersing the entire surface 504 or continuous piece 502 in a bath of the oxidizing agent. In the third step 540, only a portion of the upper surface 504 corresponding to a predetermined pattern is exposed to UV irradiation. For example, a uniform UV irradiation field 542 may be incident on a photomask 544 that has an open or transparent area 546 that allows light to pass through to expose the upper surface of the first section 548, and blocks light to expose the upper surface of the second section 550.

[0074] The combination of oxidizing agent and UV irradiation in the first section 548, rather than the second section 550, causes photocatalytic oxidation only in the first section 548. The modified wood 553 (e.g., photonic wood) thus obtained in step 552 has a first section 554 that is lignin-modified in situ and substantially whitened, and a second section 556 that retains its natural lignin and is substantially non-white (e.g., the color of natural wood). In some embodiments, the modified wood 553 in step 552 can be used as is, for example, as a thermal insulator or optical reflector.

[0075] Alternatively, in some embodiments, the modified wood 553 is subjected to further processing in the final step 558. For example, the wood 553 can be impregnated with a refractive index matching polymer to form a patterned transparent wood composite 560 having a transparent first section 562 and adjacent translucent or opaque second section 564. For example, as described above with respect to Figure 1A, the polymer can be impregnated into the microstructure of the modified wood 553 by immersing it in a liquid polymer or polymer precursor and applying a vacuum for a certain period of time.

[0076] Figure 5D shows an exemplary batch operation for producing a transparent wood composite. In the second step 566, the oxidizing agent may be applied to the entire upper surface 504 of a continuous piece of wood 502 via the application of a controlled amount of the oxidizing agent using a brush 514 or other mechanism, for example, in the same manner as in the second step 536 in Figure 5C and / or in the same manner as described above for the second step 506 in Figure 5B. Alternatively, the application of the oxidizing agent may be carried out by immersing the entire surface 504 or the continuous piece 502 in a bath of the oxidizing agent. In the third step 568, the entire upper surface 504 may be exposed to UV irradiation 518 from a natural or artificial light source. The combination of oxidizing agent and UV irradiation on the entire continuous piece 502 causes photocatalytic oxidation of all parts (e.g., without pattern). The modified wood 572 (e.g., photonic wood) obtained in step 570 is lignin-modified as a whole in situ and substantially whitened. In some embodiments, the modified wood 572 in step 570 can be used as is, for example, as a thermal insulator or optical reflector. Alternatively, in some embodiments, the modified wood 572 is subjected to further processing in the final step 574. For example, a refractive index matching polymer can be impregnated into the wood 572 to form a transparent wood composite 576. For example, as described above with respect to Figure 1A, the polymer can be impregnated into the microstructure of the modified wood 572 by immersing it in a liquid polymer or polymer precursor and applying a vacuum for a certain period of time.

[0077] In some embodiments, transparent wood composites (with or without patterns) can be manufactured using semi-continuous or continuous manufacturing processes. For example, Figure 6 shows an exemplary manufacturing setup 600 employing a continuous operation. The natural wood 602 may be in the form of logs or cylindrical rods, with their internal cavities extending perpendicular to the plane of the paper. The natural wood 602 may be continuously cut by a rotary lathe 604 to separate, for example, continuous thin layers 606 of natural wood for subsequent processing. The natural wood layers 606 may be transported to the next step in the manufacturing process, for example, to a station 608 for surface application of a controlled amount of liquid oxidizer 612 using a brush 610 or other mechanism.

[0078] After station 608, the wood layer 606 may be transported to the next station, for example, a UV exposure station 614. The UV exposure station 614 may include an artificial light source 616 and one or more optical elements 620 (e.g., reflectors) designed to irradiate the wood with a substantially uniform light beam 618. Alternatively, in some embodiments, the UV exposure station 614 utilizes natural sunlight instead of using an artificial light source. Similar to the embodiments described above, the combination of UV exposure and an oxidizing agent in the wood results in photocatalytic oxidation that modifies the lignin in situ, particularly removing its chromophore, without substantially reducing the lignin content. In some embodiments, the size of station 614 and the transport rate of the wood layer 606 through station 614 may correspond to a desired UV exposure time (e.g., 1-2 hours). Thus, the time from when a portion of the layer 606 enters station 614 until it exits polymer penetration station 624 corresponds to the exposure time for in situ lignin modification.

[0079] In some embodiments, the modified wood 622 obtained at station 614 can be used without further processing. Alternatively, in some embodiments, the modified wood 622 may be further transported to a subsequent station, such as a polymer station 624, which contains a liquid polymer or polymer precursor 626 in a chamber 628 (e.g., a vacuum chamber). The penetration of the modified wood 622 into the cellulosic microstructure forms a transparent wood composite 630.

[0080] [Manufacturing examples and experimental results] [[First Example: Transparent Wood Composite with Natural Pattern]] In particular, we fabricated transparent wood composites with natural patterns (also called aesthetically pleasing wood) based on two different cuts of wood: radial (R) cuts in which aligned channels of cellulosic microstructure extend perpendicular to the main surface (e.g., the surface exposed to transmitted incident light), and longitudinal (L) cuts in which aligned channels of cellulosic microstructure extend parallel to the main surface. Douglas fir was selected because of the prominent contrast in color and density between the earlywood (EW) and latewood (LW) sections. As shown in Figure 7A, the cellulosic microstructure of Douglas fir showed a clear boundary between the EW and LW sections. The microstructure of the EW sections (as shown in Figures 7A and 7B) differed from that of the LW sections (as shown in Figures 7A and 7C), with the EW sections having thinner sidewalls (e.g., thickness ≤ 3.8 μm in a plane substantially parallel to the radial direction of the wood) and larger lumens (e.g., cross-sectional dimensions in a plane substantially parallel to the radial direction of the wood). The distribution of tracheids in the wood (e.g., hollow tubular structures shown in Figure 7D) varied depending on the specific wood section, with the EW sections having a lumen diameter range of approximately 20 μm to 80 μm (see Figure 7E), and the LW sections having a lumen diameter range of approximately 5 μm to 35 μm (Figure 7F). Thus, the different pore size distributions indicate different densities in the EW and LW sections.

[0081] For the analysis of the deligninization effect, continuous R-cut wood blocks of 60mm x 60mm x 2mm Douglas fir were used. Coloring components (mainly lignin and extracts) were removed from the bulk wood using an acidic NaClO2 (80%) solution. The solution was prepared by dissolving NaClO2 powder in deionized (DI) water and adjusting the pH (below 4.6) with acetic acid. Each wood sample was placed in the boiling NaClO2 solution and left for a certain period (e.g., 2 hours) until the EW section turned white. The deligninized wood samples were then rinsed at least three times with DI water and stored in ethanol until further processing. To form wood composites with a natural pattern, epoxy resin (e.g., AeroMarine 300 / 21 epoxy, a clear, low-viscosity cycloaliphatic epoxy from Aeromarine Products, San Diego, California) was impregnated into the treated wood samples. The epoxy resin was allowed to solidify for approximately 24 hours to obtain wood composites with a natural pattern.

[0082] Immersion in a boiling NaClO2 solution for approximately two hours allowed for different (e.g., spatially selective) deligninization between EW and LW sections (at least partially based on the density difference between EW and LW). After two hours of treatment, the EW sections became almost completely white, while the LW sections retained their color due to residual lignin and other coloring components. The main factor contributing to spatially selective deligninization was the inherent structural difference between the EW and LW sections, which led to faster diffusion of the solution in the EW sections than in adjacent LW sections. After two hours of immersion in a boiling NaClO2 solution, the weight of each wood sample decreased by approximately 13.5%. However, the nanoscale and macroscale features of the natural wood (e.g., cellulosic microstructure) were substantially preserved. Longer treatment times (e.g., approximately 10 hours) were required to completely whiten the LW sections, and the weight loss increased accordingly (e.g., a weight loss of approximately 35%). With longer processing times, the structural integrity of the deligninized wood is not sufficiently maintained, and the EW section (e.g., 284.6 kg·m)-3 ) and the clear density difference with the LW section (e.g., 846 kg·m -3 ), as well as the absence of lignin in both the EW section and the LW section, led to the deterioration of mechanical properties.

[0083] To evaluate the distribution of lignin in the skeleton of softwood after spatially selective delignification, Raman spectroscopy imaging and vertex component analysis (VCA) were used in combination. Figure 7G shows the Raman spectra obtained for both the EW and LW sections of both natural wood and spatially selectively delignified wood. In particular, Figure 7G shows the 1598 cm -1 , 1656 cm -1 , and 1269 cm -1 (marker bands for aryl OH and aryl OCH3 of the guaiacyl (G) unit in lignin), which are attributed to aromatic C=C stretching, coniferyl alcohol C=C, C=O stretching, and C-H bands of C=C, aromatic C=C stretching, respectively. Compared with the EW and LW sections in natural wood, the typical lignin bands in the cell walls of the EW section of the spatially selectively delignified wood almost disappeared, and the typical lignin bands in the cell walls of the LW section of the spatially selectively delignified wood remained. On the other hand, each cellulose peak (e.g., 1095 cm -1 (C-O-C stretching vibration)) remained relatively unchanged after treatment with NaClO2. From these results, it can be seen that in the spatially selectively delignified wood, most of the lignin in the EW section was removed and a small amount of lignin remained in the LW section, forming a natural pattern in the continuous wood block.

[0084] Using the same procedure as described above, continuous wood blocks of Douglas fir were fabricated by L-cutting them to have a linear pattern rather than an annular pattern (using the quarter-slice cuts in Figure 4C). The efficient, spatially selective deligninization process provided excellent structural integrity and facilitated the large-scale production of transparent wood composites with L-cut natural patterns. For example, continuous wood blocks of transparent wood composites with L-cut natural patterns measuring 320 mm × 170 mm × 0.6 mm were fabricated, which is significantly larger than the conventional production of transparent wood using deligninized wood as a framework. The transparent wood composites with L-cut natural patterns were optically transparent, with a total transmittance of 87% at 600 nm (e.g., from both the EW and LW sections) and an optical haze of 65%.

[0085] The transparent wood composite, with its natural L-cut pattern, exhibited a large number of aligned microchannels along the wood growth direction after successful infiltration. In the cross-sectional view, the lumens in the LW section were much smaller than those in the EW section, but all lumens were dense. Furthermore, the channels and openings in each section were completely filled with polymer (e.g., epoxy resin). This acts as an adhesive, creating a strong interaction between the cell wall and the polymer itself. Further Raman spectroscopy imaging was performed to identify the distribution of the impregnating polymer in the cells of the resulting wood, including the cell corners (CC), composite intermediate film (CML), cell wall (CW), and lumens. According to the corresponding Raman spectra in Figure 7H, the strong signal peak in the lumen indicates epoxy bonding expansion and contraction, particularly at 640 cm⁻¹. -1 (Aromatic CH out-of-plane deformation), 1001 cm -1 (Polyamidoamine adduct, amino group), and 1608 cm -1 It exhibited an aromatic ring respiration pattern. Since polymer signals were detected in CML / CC and CW, it is thought that the polymer sufficiently penetrated the wood cells and formed a strong interface with cellulose in the deligninized wood skeleton.

[0086] The retrospective cellular structure of spatially deligninized wood resulted in unique anisotropic mechanical characteristics. For example, transparent wood composites with natural patterns formed from R-cut wood showed significantly improved tensile strength (e.g., 21.56 MPa) compared to R-cut natural wood (e.g., 6.24 MPa), and transparent wood composites with natural patterns formed from L-cut wood showed even higher tensile strength (e.g., 91.95 MPa). The toughness of transparent wood composites with natural patterns formed from R-cut and L-cut wood was 0.523 MJ m, respectively. -3 and 2.733 MJ m -3 That was the case.

[0087] Furthermore, the non-uniform lignin distribution and cellular structure between the EW and LW sections in transparent wood composites with natural patterns can result in non-uniform transmittance. As shown in Figure 7I, eight locations within the EW sections (1-8) and LW sections (1'-8') of a transparent wood composite with natural patterns formed from R-cut wood were selected, and the light transmittance at 600 nm was measured. The LW sections showed lower transmittance (e.g., approximately 68% on average) than the EW sections (e.g., approximately 86% on average). Despite the lower transmittance values ​​in the LW sections, the LW sections only slightly reduced the average transmittance of the transparent wood composite with natural patterns with respect to light in the visible light spectrum (e.g., wavelengths of at least 600 nm to 700 nm (inclusive)).

[0088] Furthermore, by retaining lignin in the LW section, a unique UV-blocking capability can be imparted to transparent wood composites with a natural pattern (for example, for wavelengths in the range of 200nm to 400nm (including both ends)). This can be adjusted by the timing of the deligninization treatment. For example, when a continuous block of wood with a thickness of 2 mm was subjected to deligninization treatment for less than 2 hours, the subsequent transparent wood composite was able to block almost 100% of the UVC (200nm to 275nm) and UVB (275nm to 320nm) spectra, and almost all of the UVA (320nm to 400nm) spectrum. However, when the deligninization treatment time was increased to, for example, 9 hours, the UVA blocking capability of the resulting transparent wood composite decreased significantly, as shown in Figure 7K. This excellent UV-blocking property is due to the presence of phenylpropane structures and phenolic hydroxyl groups in the lignin molecules that have UV-absorbing capabilities. As a result, the transparent wood composite material with a natural pattern, formed from continuous wood blocks subjected to a 2-hour delignin treatment, exhibited a unique combination of characteristics: good UV absorption in the 200nm-400nm range (e.g., over 80%), high average transparency at 600nm (e.g., over 80%), and low reflectivity to visible wavelengths (e.g., less than 20%).

[0089] Furthermore, transparent wood composites with natural patterns exhibited anti-glare and light-guiding capabilities. For example, as shown in Figure 7L, transparent wood composites with natural patterns scattered light significantly forward, resulting in an optical haze of less than 93%. Because transparent wood composites inherit the aligned microstructure of natural wood, when refractive index-matching polymers (e.g., epoxy) fill the wood cavities, light can propagate along microchannels. These microchannels function as lossy waveguides, which gives transparent wood composites the properties described above.

[0090] The pattern of transparent wood composites is defined by the natural patterns of the EW and LW sections in a continuous piece of the original wood. However, other types of patterns can be achieved by stacking multiple layers 700 of transparent wood composites together. Each of these layers may be from the same wood, from the same wood species (e.g., both Douglas fir but different woods), or from different softwoods (e.g., one fir and the other pine). For example, as shown in Figure 7M, a grid pattern in assembly 704 can be formed by stacking two (or more) layers 700a and 700b having patterns rotated relative to each other in a stack 702. Based on high transparency and an inherently superior aesthetic appearance, this capability can enable potential applications in ceilings with patterns.

[0091] At the same time, wood, which has a superior aesthetic appearance, also offers better insulation than glass, thus improving energy efficiency. For example, transparent wood composites with natural patterns have a thermal insulation of 0.24 W·m in the radial direction (for example, perpendicular to the longitudinal growth direction). -1 K -1 This shows the thermal conductivity. This is lower than in the case of growth in the longitudinal direction (e.g., 0.41 W·m). -1 K -1 The isotropic thermal conductivity of typical window glass (e.g., 1 W·m) is shown below. -1 K -1 It is lower than the following. The anisotropic heat transport of transparent wood composites, combined with such low thermal conductivity, is useful for replacing glass in energy-efficient buildings.

[0092] To demonstrate the use of transparent wood composite materials with natural patterns as building materials with high transparency and low haze, a model house was constructed with skylights made of glass and transparent wood composite materials. Using an external white light source directed towards the skylight, the light intensity at each point within each model house was detected and compared. In the model house employing glass skylights, the maximum light intensity (e.g., 56.8 mW·cm) was measured. -2 ) is the minimum luminous intensity (for example, 3.4 mW·cm²).-2 The light intensity increased to approximately 17 times that of the previous model, resulting in uneven illumination. In contrast, the model house using a transparent wood composite skylight had a maximum light intensity of 48.2 mW·cm². -2 The minimum light output is 20.9 mW·cm². -2 As a result, the diffuse light distribution became more uniform.

[0093] Furthermore, the weather resistance of transparent wood composites with natural patterns was evaluated by exposing them outdoors for three weeks and measuring their optical and mechanical properties. In transparent wood composites formed from R-cut wood, the transmittance after exposure decreased slightly compared to before exposure, and the haze increased to 94% to 98% at wavelengths in the range of 400 nm to 800 nm. Transparent wood composites formed from L-cut wood showed similar changes in transmittance and haze properties after exposure. Similarly, the aesthetically superior wood-L also showed similar trends in transmittance and haze. However, exposure did not affect the mechanical properties of any of the cut pieces of transparent wood composites. Rather, no significant degradation in the strength of the transparent wood composites was observed due to exposure, indicating that this composite has short-term weather resistance.

[0094] In the examples described above, softwood was used to utilize spatially selective deligninization based on the original portion within a continuous wood fragment. While both hardwood and softwood are fundamentally suitable, they have significantly different structures, as hardwood consists of vessels and fibers, while softwood consists mainly of tracheids. For example, basswood, a type of hardwood, has a substantially uniform cell wall thickness of 5.8 μm, which is much thinner than the cell wall thickness of the LW section of Douglas fir. Furthermore, the vessel channels in basswood have a larger inner diameter than the relatively narrow tracheids of Douglas fir, and the vessel channels exhibit a bimodal pore size distribution. As a result, the reactions in the EW and LW sections of basswood proceed substantially in sync, and almost no apparent wood pattern is retained after 2 hours of treatment. Similar results were obtained with balsa wood (another type of hardwood with bimodal pores, resulting in substantially uniform solution diffusion). However, hardwoods that exhibit substantial differences in density, porosity, cell wall thickness, luminal surface dimensions, or any combination thereof, resulting in different solution diffusion or reaction efficiencies between different naturally occurring sections therein, may be used to form transparent wood composites having natural patterns according to embodiments of the subject matter of this disclosure.

[0095] [[Second Example: IN SITU Lignin-Modified Wood]] Modified wood (also called in situ lignin-modified wood, lignin-modified wood, or photonic wood) was fabricated by chemically modifying natural lignin in continuous wood blocks in situ using a UV-assisted photocatalytic oxidation method. During the UV-assisted photocatalytic oxidation process, conjugated double bonds were cleaved, removing the chromophore of lignin while retaining the bulk aromatic skeleton of lignin. This provides mechanical strength. Thus, in the modified wood, while retaining a large portion (e.g., over 80%) of the original wood, the removal of the chromophore imparted unique optical properties. In particular, compared to deligninization techniques in prior art used to generate the optical properties of wood, the modified wood exhibited optical whiteness (e.g., reflectance of over 90% for light with wavelengths in the range of 400 nm to 800 nm (inclusive)), intact cellulosic microstructure, improved mechanical strength (e.g., wet tensile strength of less than 20 MPa), excellent water stability, and improved scalability (e.g., up to 2 meters).

[0096] In natural wood, vertically aligned wood channels allow H2O2 and UV light to efficiently penetrate the wood structure, enabling rapid and thorough decolorization in less than 7 hours (e.g., 1 to 6.5 hours depending on the thickness of the continuous wood fragments perpendicular to the surface of the wood fragment into which UV light is incident). Furthermore, H2O2-printed wood combined with UV light irradiation (e.g., by using a paperboard engraving as a mold for applying H2O2 to the wood surface) allowed for selective decolorization of the wood. This made it possible to directly generate regions with custom, predetermined patterns and different optical properties within continuous wood fragments.

[0097] Due to its low density and hierarchical porous microstructure, balsa wood was used to prepare the modified wood, although other hardwoods or softwoods could also be used. First, samples of continuous wood blocks were immersed in a 30% H2O2 solution with a 10% NaOH solution added to impregnate the balsa wood samples with H2O2. A small amount of alkali was able to accelerate the decomposition of H2O2 without causing substantial lignin removal from the balsa wood. Next, each H2O2-impregnated balsa wood sample was exposed to UV irradiation using an artificial light source (UVA band, 20W power) until the sample turned completely white. For example, natural balsa wood changed from brown to completely white after about 2 hours of UV exposure (in combination with H2O2 exposure). In contrast, when H2O2 was used without UV light, the wood changed color to yellow. Furthermore, lignin contains many light-sensitive chromophores (such as quinone groups and conjugated double bonds), making it easy to absorb photons from UV light and generate chromophore radicals. Therefore, photo-excited chromophore radicals enable photocatalytic oxidative decomposition, allowing for the removal of the brown parts of natural wood. On the other hand, despite lignin's sensitivity to UV irradiation, irradiation with UV light alone did not significantly change the wood's color. Additionally, when H2O2 treatment and UV exposure were used in combination, 10 hours of H2O2 exposure was insufficient to modify natural balsa wood to the same level of whiteness achieved by the combination of H2O2 and UV exposure alone. This indicates that chemical oxidizing agents alone cannot completely bleach wood, or at least cannot bleach it on the same timescale as the combination of chemical oxidizing agents and UV exposure.

[0098] Furthermore, the combination of H2O2 and UV exposure allowed for modification of the optical properties of the wood without significantly removing lignin. This resulted in improved mechanical strength compared to conventional deligninization techniques. The component content of the modified wood was measured by acid hydrolysis, and acid-insoluble lignin (crasone lignin) was determined by acid hydrolysis. Figure 8A shows that in UV-assisted photocatalytic oxidation treatment, the normalized lignin content decreased only slightly with increasing treatment time. For example, two hours after UV-assisted photocatalytic oxidation (sufficient time to completely whiten the sample), the lignin content in the modified wood was 19.29 wt%. This corresponds to less than 82% of the original lignin content in the starting material of natural balsa wood (e.g., 23.5 wt%). Also, as shown in the Fourier transform infrared spectroscopy (FTIR) spectrum in Figure 8B, the modified wood (photonic) had a 1592 cm⁻¹ spectrum. -1 , 1505cm -1 , and 1430cm -1 It showed an absorbance peak. This indicates that the aromatic skeleton lignin structure was well preserved.

[0099] Furthermore, the chemical structure of the modified wood was analyzed using X-ray diffraction spectroscopy (XDS) and X-ray photoelectron spectroscopy (XPS). X-ray diffraction (XRD) patterns were collected using a Rigaku Ultima III (operating tube voltage 40kV, tube current 30mA, Cu Kα, λ=1.5406Å) equipped with a curved detector from Rigaku Americas. As shown in Figure 8C, the XRD pattern of the cellulose crystal structure in the modified wood showed diffraction peaks at 16° and 22.6°. This represents the original cellulose crystal lattice type I structure (CrI), confirming that the crystal structure had not changed from the original wood due to the UV-assisted photocatalytic oxidation process. In the XPS experiment, the peak positions were calibrated relative to the C1s binding energy of 284.6eV. Figure 8D shows the C1s spectra of natural wood and modified wood. The XPS spectrum of the photonic wood had a high energy shift compared to the starting material. The calculated oxygen / carbon (O / C) ratio changed from 0.26 to 0.42 after UV-assisted photocatalytic oxidation treatment, indicating that the modified wood had a higher proportion of oxygen atoms and a lower proportion of carbon atoms. This is thought to be due to an increase in the amount of OC=O and C=O groups resulting from oxidation reactions on the lignin surface. From this, it is thought that the conjugated double bond (C=C) of the chromophore opened, and an unconjugated carboxyl group was formed.

[0100] These results confirm that UV-assisted photocatalytic oxidation, in addition to whitening wood, has the effect of modifying lignin into a chromophore in situ, while largely preserving the lignin skeleton. Unlike other non-in situ lignin modification techniques, the disclosed technique enables in situ modification of natural lignin. This consists of a phenyl skeleton and oxygen-containing branches, linked by a series of CO and CC bonds. Such an intact lignin structure facilitates the removal of its chromophore while preserving the lignin skeleton structure as much as possible during the photocatalytic oxidation process.

[0101] As described above, natural wood can have large vessel channels with diameters of several hundred micrometers (100 μm to 300 μm) and small fibrous lumens with diameters of several micrometers (20 μm to 50 μm). This can be modified with pits of varying sizes (0.8 μm to 10 μm). These hierarchical and interconnected microstructures function as efficient pathways for the photocatalytic oxidation process, promoting H2O2 penetration and UV light capture, allowing for the production of modified wood through an efficient synergistic reaction. Furthermore, the wood skeletal structure with hierarchical pores was maintained even after the photocatalytic oxidation process. In particular, the cell wall thickness of the modified wood (less than 2.06 μm) was similar to that of the natural balsa wood starting material (2.09 μm). For comparison, deligninized wood was prepared by immersing natural balsa wood in a boiling chemical solution (e.g., a 5 wt% NaClO2 aqueous solution with acetic acid added to adjust the pH to 4.6 or less) until it was completely white. As shown in Figure 8F, the cell walls of such deligninized wood became significantly thinner after treatment (less than 1.46 μm), accompanied by a major change in the underlying cellulosic microstructure.

[0102] To investigate the uniformity of the treatment with respect to the thickness of the modified wood, a cross-section of a continuous wood block (38mm × 30mm × 9mm) of modified wood was taken in the longitudinal growth direction and divided into three sections: section "I" corresponding to the 3mm thick portion adjacent to the top surface of the wood block exposed to UV, section "III" corresponding to the 3mm thick portion adjacent to the bottom surface of the wood block opposite the top surface, and section "II" corresponding to the 3mm thick portion between sections I and III. No significant visual differences were observed between the three sections. All showed the same level of whiteness, indicating that the wood was consistently decolorized by UV-assisted photocatalytic oxidation. Furthermore, the microscopic structures of the three sections were also similar, indicating that they were the microstructure of intact wood. In addition, FTIR analysis showed that the three sections had the same composition and retained the bulk structure of lignin. Furthermore, the reflectance spectra shown in Figure 8E show that all three sections showed high reflectance of visible light (90%~96%). Without being bound by any particular theory, the uniform properties of modified wood are thought to be due to the rapid penetration of O· / HOO·· made possible by the channel structure of natural wood, and the efficient movement of UV light deep into the interior of the wood.

[0103] Compared to deligninization methods, the disclosed photocatalytic oxidation technology exhibited several superior properties. First, the use of H2O2, an environmentally friendly oxidizing agent that decomposes into water and oxygen without generating toxic gases or liquids, is considered more environmentally friendly than deligninization methods (e.g., using NaClO2 solutions which can generate large amounts of harmful chlorine gas). Also, the processing time required for photocatalytic oxidation can be substantially shorter than that required for deligninization. For example, the disclosed photocatalytic oxidation can decolorize (whiten) a 5mm thick wood block in as little as 3.8 hours, whereas deligninization methods may require at least 6 hours to achieve similar decolorization. Furthermore, the photocatalytic oxidation process can retain lignin content better than deligninization by selectively removing chromophores while preserving the bulk aromatic structure of lignin (82% vs. 1.4%). In fact, by retaining most of the lignin after treatment, the modified wood can retain the original cellulosic microstructure of the wood, as shown in Figure 8F. In contrast, the cell walls of deligninized wood are characterized by large gaps and partial kinks, resulting in a loss of structural form.

[0104] The preserved lignin in modified wood acts as a mechanical binder, providing mechanical strength and preventing the wood from decomposing. After immersing wood samples in ultrapure water for 20 minutes to remove excess moisture from the sample surface, mechanical testing was performed. Tensile properties of natural wood, modified wood, and deligninized wood samples were measured using a Tinius Olsen H5KT testing machine. The dimensions of the tensile samples were approximately 50 mm × 5 mm × 1.5 mm. The samples were stretched along the length of the sample at a test speed of 5 mm per minute until fracture. Under these wet conditions, the modified wood exhibited a tensile strength of 20 MPa (along the longitudinal growth direction). This is 20 times the tensile strength of completely deligninized wood (1 MPa) and essentially the same as the tensile strength of unmodified natural wood. In this case, the in situ modified lignin in the modified wood was able to bond the cellulose fibers together, improving the tensile properties of the wood compared to deligninized wood.

[0105] The compressive properties of photonic wood and deligninized wood samples were measured using a Tinius Olsen H5KT testing machine. The dimensions of the tensile sample were approximately 20 mm × 10 mm × 10 mm. The sample was compressed at a constant test speed of 5 mm per minute along directions perpendicular and parallel to the tree's growth direction. The modified wood showed high compressive strength, supported by hard lignin, but when pressure was applied to the deligninized wood, the cell walls irreversibly collapsed. After the pressure was released, the modified wood recovered without any apparent deformation (thickness change after compression Δh = 1.5 mm). In contrast, the deligninized wood was unable to recover and showed high compressive deformation (Δh = 8.4 mm). Furthermore, a compression test was performed on a wood sample in good condition along the direction parallel to the tree's growth direction. At the same compressive displacement (1.6 mm), the deligninized wood showed cell wall collapse, but the modified wood showed no structural damage and no significant decrease in compressive strength.

[0106] In situ-modified lignin, due to the hydrophobicity of the lignin's aromatic rings, acted as a barrier against water, improving the water stability of modified wood. Water stability tests were conducted by placing natural wood blocks, modified wood blocks, and deligninized wood blocks in water. The dimensions of the wood in this experiment were 4.5 cm × 4.5 cm × 0.45 cm. Natural wood, photonic wood, and deligninized wood were placed in water simultaneously, and the thickness was recorded every minute. The deligninized wood absorbed more water, resulting in a greater change in mass than the modified wood. In this case, without the shielding of hydrophobic lignin, the loose cellulose fibers of the hydrophilic deligninized wood became sensitive to water. On the other hand, the high water absorption rate of the deligninized wood made the change in material thickness more pronounced. The water absorption rate of samples with one end of the wood placed in a methylene blue (MB) solution was also measured. The amount of MB absorbed was highest for the deligninized wood, followed by the modified wood. This further demonstrates that deligninized wood is more susceptible to water penetration because it lacks hydrophobic lignin.

[0107] To investigate water stability, samples were immersed in water for three weeks. Deligninized wood completely decomposed into short fibers, while modified wood maintained its shape without significant change. Because it lacked lignin, water penetrated the deligninized wood, disrupting the accessible and loose cellulose hydrogen bonds and weakening its mechanical properties. Conversely, the hydrophobic and bonding properties of lignin, which cross-links microfibers, prevented water from breaking the cellulose hydrogen bond structure, resulting in improved mechanical properties and superior water stability for photonic wood.

[0108] In the above-described fabrication example, the entire continuous block of wood was modified. However, using photocatalytic oxidation technology, adjacent sections within a continuous block of wood can be formed with different properties according to a predetermined two- or three-dimensional pattern independent of the wood's natural pattern. In particular, since both UV light and a chemical oxidizing agent (H2O2) are used to achieve decolorization within a specific processing time, the controlled application of both to a specific part of the wood can define the resulting properties. For example, H2O2 can be printed on the surface of natural wood in a specific pattern (e.g., using a carved cardboard mold) (e.g., by brushing, painting, spraying, or applying to the surface without immersing the entire continuous block of wood). This surface is then irradiated with UV light. Sections of wood that receive both UV and H2O2 are modified, while sections that receive only one or neither remain unmodified. For example, a pattern was printed on the surface of a continuous block of wood using 30% H2O2, and then the surface was exposed to UV light to form modified wood with the pattern. Figures 8G and 8H showed Chinese knot patterns and star patterns formed on each of the following continuous wood blocks using this technique. Here, the lignin in sections 804, 808, and 812 was modified in situ, from which the chromophore was removed to become white, while the lignin in sections 802, 806, 810m, and 814 was substantially unmodified (e.g., the original form of lignin). Alternatively, H2O2 can be applied to the entire wood block, and then the surface of the natural wood can be UV irradiated in a specific pattern. Thus, natural wood can be selectively decolorized on-demand by this easy, sustainable, large-scale, and low-cost synergistic photocatalytic oxidation treatment.

[0109] [[Third Example: Transparent Wood Composite Material]] Modified wood was prepared by chemically modifying natural lignin in a continuous block of wood in situ using UV-assisted photocatalytic oxidation. Next, a refractive index matching polymer was impregnated into the modified wood to form a transparent wood composite (also called in situ lignin-modified transparent wood composite, transparent wood composite with an artificial pattern, or transparent wood). Balsa wood logs were cut transversely and longitudinally to obtain wood slices (with a thickness of 0.6 mm to 3.5 mm (including both ends)). For each balsa wood slice, in order to improve the oxidation efficiency of H2O2, a small amount of NaOH (2 ml to 3 ml at a concentration of 10 wt%) was applied to the top surface (perpendicular to the thickness direction) (e.g., by brushing) before brushing with H2O2. Then, H2O2 was brushed onto the top surface of each wood slice (15 ml or more at a concentration of 30 wt%, the amount depending on the thickness of the wood), and the top surface was then irradiated with light until the sample was completely white. For UV irradiation of the modified wood, a UV lamp emitting wavelengths of 380nm to 395nm was used. For example, 15 ml of H2O2 (30 wt%) was brushed onto a 200 mm × 10 mm × 0.6 mm sample of natural balsa wood, and then exposed to UV light for 1 hour until the natural wood color completely turned white. This process removed the chromophores in the lignin, changing the wood color from brown to white. Next, the treated wood fragments were immersed in ethanol for 5 hours to remove any remaining chemicals, and then transferred to toluene to replace the ethanol in the wood. Subsequently, each of the treated wood fragments was impregnated with epoxy resin (e.g., AeroMarine 300 / 21 epoxy, a clear, low-viscosity cycloaliphatic epoxy system from Aeromarine Products, Inc. (San Diego, California)) under vacuum for 1.5 hours. Finally, the epoxy-impregnated wood samples were stored at room temperature to allow the epoxy to fully cure.

[0110] Figure 9A shows the FTIR spectra of lignin-modified wood compared to natural wood, and the subsequent formation of transparent wood. (Approximately 1595 cm²) -1 , 1505cm -1 , and 1435cm -1The absorption peak is attributed to the aromatic vibrations of lignin. This confirms that the aromatic skeleton is maintained even when the chromophore of lignin deteriorates due to in situ lignin modification and subsequent polymer infiltration. FTIR spectrum at 1734 cm⁻¹ -1 The peak is attributed to the carboxyl group of hemicellulose (xylan / glucomannan) at 1235 cm⁻¹. -1 The peaks can be attributed to the uronic acid groups of hemicellulose or the ester bonds between lignin and the carboxyl groups of hemicellulose. Compared to natural wood, lignin-modified wood has a 1734 cm² peak. -1 Peak disappearance and 1235cm -1 The decrease in peak intensity indicates that the hemicellulose in the natural wood was partially dissolved / removed by the photocatalytic oxidation treatment.

[0111] Figure 9B compares the lignin content of lignin-modified wood and the subsequent transparent wood formed with that of natural wood. The lignin content of the natural wood and lignin-modified wood samples was 23.5% or less and 19.9% ​​or less, respectively. This confirms that the lignin structure is largely preserved after photocatalytic oxidation treatment. The preserved lignin acts as a binder to enhance the mechanical properties of lignin-modified wood and can provide a strong wood skeleton for subsequent polymer penetration when forming transparent wood composites.

[0112] Figures 9C–9E show scanning electron microscopy (SEM) images of natural wood, lignin-modified wood, and transparent wood. As shown in Figure 9C, natural wood exhibits a 3D hierarchical and interconnected porous microstructure, characterized by microchannels (e.g., lumens) with cross-sectional dimensions (e.g., diameter) ranging from 15 μm to 300 μm. This unique porous microstructure is beneficial for the rapid penetration / diffusion of H2O2 solution and efficient capture of UV light within the wood's microchannels, allowing for efficient removal of light-absorbing chromophores during the photocatalytic oxidation process. As shown in Figure 9D, lignin-modified wood substantially retains the porous microstructure of wood, with cross-sectional dimensions (e.g., diameter) of microchannels within the lignin-modified wood ranging from 10 μm to 270 μm. As shown in Figure 9E, epoxy resin can penetrate the pores of lignin-modified wood. This allows for the formation of a dense, compact composite structure, which helps suppress light spawning and improve light transmittance.

[0113] In particular, transparent wood formed from wood cut radially / transversely (T) (e.g., with dimensions of 70mm × 30mm × 1.5mm) and transparent wood formed from wood cut longitudinally (L) (e.g., with dimensions of 400mm × 110mm × 1mm) both exhibited excellent optical properties. Figure 9F shows the light transmittance of natural wood and transparent wood from 200nm to 2000nm. Transparent wood along the L and T directions had high light transmittance of less than 90% for wavelengths in the range of 400nm to 800nm ​​(including both ends). In contrast, natural wood in the same range showed lower light transmittance (e.g., less than 6% in the L direction and less than 36% in the T direction). Because the light-absorbing chromophore of lignin is removed by photocatalytic oxidation, almost all visible light is transmitted through the transparent wood. Therefore, as shown in Figure 9G, the absorptivity of the transparent wood approaches 0% for wavelengths in the range of 400nm to 800nm ​​(including both ends), which is much lower than the absorptivity of natural wood in the same range. On the other hand, due to the preservation of the cellulose microstructure, the transparent wood exhibits improved haze properties along with high transparency. For example, Figure 9H shows the transmittance haze values ​​of the transparent wood along the L and T directions. Here, each cut of the transparent wood showed haze values ​​in the range of 60% to 80% for wavelengths in the range of 400nm to 800nm ​​(including both ends).

[0114] In the examples described above, balsa wood was used, but transparent wood can be made from any type of hardwood or softwood. In fact, transparent wood with excellent optical transparency has been made from other wood species with different densities, particularly oak and poplar. This suggests the universality of this approach. Furthermore, transparent wood can retain the aligned channels of the original wood's microstructure, guiding light propagation along the channel direction and providing anisotropic light transmittance.

[0115] As mentioned above, retaining lignin within transparent wood composites can improve their mechanical properties. The mechanical properties of natural wood and transparent wood were measured when the tensile direction was changed. The tensile strengths of natural wood along the L and T directions were 24.5 MPa and 0.7 MPa, respectively, while the tensile strengths of L-transparent wood and T-transparent wood samples were 46.2 MPa and 31.4 MPa, respectively (corresponding to strength improvements of 1.8 and 44.8 times, respectively, compared to natural wood). Furthermore, L-transparent wood and T-transparent wood were found to have a tensile strength of (L: 0.263 MJ m) compared to natural wood. -3 T:0.033MJ m -3 ) compared to 0.933 MJ m -3 and 1.643 MJ m -3 This demonstrated a significant improvement in toughness. The toughness of transparent wood L was lower than that of transparent wood T, which is due to the smaller elongation at break of the L sample (3.4% < 7.4%). Benefiting from its high mechanical strength, the transparent wood was very flexible and did not break even when bent at angles greater than 90° (e.g., up to 180°).

[0116] Conventional solution-based deligninization methods immerse the entire wood block in a chemical solution, making it difficult to selectively bleach specific areas of the material. In contrast, combining surface application of a liquid oxidizing agent (e.g., brushing of H2O2 onto the wood) with UV light irradiation allows for selective in situ lignin modification of specified areas of a wood sample. This enables the preparation of transparent wood composites with a predetermined, unique pattern, independent of the natural pattern beneath the wood. In particular, in continuous wood blocks, a pattern can be selectively and precisely formed to define lignin-modified and unmodified (e.g., natural lignin) areas, and then a patterned transparent wood composite can be formed by impregnating the continuous wood blocks with a polymer. In polymer-impregnated continuous wood blocks, the lignin-modified areas exhibited relatively high light transmittance (e.g., less than 90% at visible wavelengths), while the unmodified areas exhibited light transmittance similar to natural wood (e.g., 6% to 36% at visible wavelengths).

[0117] To form a transparent wood composite with a pattern, first, the desired pattern was drawn on the surface of a natural wood sample using a brush as "ink." Then, UV light was shone on the surface of the wood to whiten the area beneath the brushed surface. Next, epoxy resin was impregnated into the microchannels of the lignin-modified wood to obtain a transparent wood composite with the desired pattern. For example, Figure 9I shows a transparent L wood composite 900 having a pattern in the shape of a yin-yang symbol using the method described above. The lignin in section 902 was modified in situ, and the chromophore was removed from it to make it white, while section 904 was substantially unmodified (e.g., the original form of lignin). By impregnating with polymer, section 902 can be made transparent, while section 904 can remain substantially opaque.

[0118] In the above-described embodiment, an artificial UV light source was used, but sunlight can also be used as the UV light source. Of the UV light (100nm to 400nm) emitted from the sun, more than 95% of the wavelengths that reach the Earth's surface are in the UVA region (e.g., 315nm to 400nm), and this wavelength is effective in exhibiting the desired photocatalytic effect. For example, using sunlight (global solar UV index: 7 to 8), three large pieces of balsa wood (1m in length) were in situ lignin-modified in just one hour of exposure. Subsequently, by impregnating them with a polymer, the whitened modified wood sections were transformed into highly transparent wood composite sections.

[0119] [Additional examples of the disclosed technology] In view of the above-mentioned implementation examples of the subject matter of this disclosure, the Application discloses additional embodiments in the following appendix. Note that a single feature of a single appendix, or two or more features of a combination of appendixes, and optionally a combination of one or more features of one or more further appendixes are also embodiments included in the disclosure of this Application.

[0120] [Note 1] A material comprising a continuous block of chemically modified wood impregnated with a polymer, Chemically modified wood retains the cellulosic microstructure of wood in its natural state, and the polymer has a refractive index that substantially matches that of cellulose, filling in the empty spaces within the microstructure. A continuous block of wood has a first section and a second section adjacent to the first section. At least one of the first section and the second section is chemically modified such that the lignin properties of the first section differ from those of the second section. The first section is substantially transparent to light having a wavelength of 600 nm. The second section is semi-transparent or opaque to light with a wavelength of 600 nm. material.

[0121] [Note 2] Materials described in either the appendices or examples of this specification, particularly the materials described in Appendix 1, wherein lignin properties mean lignin content, and the first section has a lower lignin content than the second section.

[0122] [Note 3] Materials described in either the appendices or examples of this specification, particularly the materials described in appendice 1 or 2, wherein the wood in its natural state is softwood.

[0123] [Note 4] Materials described in any of the appendices or examples of this specification, particularly materials described in any one of appendices 1 to 3, wherein a first section is substantially transparent to some or all wavelengths in the visible light spectrum (e.g., 380 nm to 750 nm), and a second section is translucent or opaque to some or all wavelengths in the visible light spectrum (e.g., 380 nm to 750 nm).

[0124] [Note 5] Materials described in any of the appendices or examples of this specification, particularly materials described in any one of appendices 1 to 4, wherein a first section has a transmittance of at least 85% to light having a wavelength of 600 nm, a first section has a transmittance of at least 80% to some or all wavelengths in the visible light spectrum (e.g., 380 nm to 750 nm), a second section has a transmittance of 70% or less to some or all wavelengths in the visible light spectrum (e.g., 380 nm to 750 nm), a second section has a transmittance of 60% or less to light having a wavelength of 600 nm, or any combination thereof.

[0125] [Note 6] A material described in any of the appendices or examples of this specification, in particular a material described in any one of appendices 1 to 5, wherein the amount of lignin removed in the first section is greater than the amount of lignin removed in the second section.

[0126] [Note 7] A material described in any of the appendices or examples of this specification, in particular a material described in any one of appendices 1 to 7, wherein the first section has 10% or less natural wood lignin, and the second section has at least 25% (e.g., at least 35%, or at least 50%) natural wood lignin.

[0127] [Note 8] A material described in any of the appendices or examples of this specification, particularly a material described in any one of appendices 1 to 7, wherein the lignin content of the first section is 3 wt% or less.

[0128] [Note 9] A material described in any of the appendices or examples of this specification, particularly a material described in any one of appendices 1 to 8, wherein the lignin content of the first section is 1 wt% or less.

[0129] [Note 10] A material described in any of the appendices or examples of this specification, particularly a material described in any one of appendices 1 to 9, wherein the lignin content in Section 2 is 7.5 wt% or more.

[0130] [Note 11] A material described in any of the appendices or examples of this specification, particularly a material described in any one of appendices 1 to 10, wherein the lignin content in Section 2 is 12.5 wt% or more.

[0131] [Note 12] A material as described in any of the appendices or examples of this specification, particularly a material as described in any one of appendices 1 to 11, wherein the first section is a material from which more than 90% of the natural lignin of the wood has been removed by chemical modification, and the second section is a material from which less than 75% of the natural lignin of the wood has been removed by chemical modification.

[0132] [Note 13] Materials described in any of the appendices or examples of this specification, in particular the materials described in any one of appendices 1 to 12, wherein the second section is a material from which 65% or less (e.g., 50% or less) of the lignin of the wood in its natural state has been removed by chemical modification.

[0133] [Note 14] A material described in any of the appendices or examples of this specification, particularly a material described in any one of appendices 1 to 13, wherein a continuous block of wood has a transmittance of 20% or less to some or all of the light having wavelengths in the range of 200 nm to 400 nm (inclusive).

[0134] [Note 15] A material described in any of the appendices or examples of this specification, particularly a material described in any one of appendices 1 to 14, wherein a continuous block of wood exhibits at least 50% haze to light having a wavelength of 600 nm.

[0135] [Note 16] A material described in any of the appendices or examples of this specification, particularly a material described in any one of appendices 1 to 15, wherein a continuous block of wood exhibits at least 65% haze to light having wavelengths in the range of 400 nm to 600 nm (inclusive), or a continuous block of wood exhibits at least 65% haze to some or all of wavelengths in the range of 400 nm to 600 nm (inclusive).

[0136] [Note 17] Materials described in any of the appendices or examples of this specification, in particular the materials described in any one of appendices 1 to 16, wherein the first section corresponds to the earlywood region of wood in its natural state, and the second section corresponds to the latewood region of wood in its natural state.

[0137] [Note 18] Materials described in any of the appendices or examples of this specification, in particular the materials described in any one of appendices 1 to 17, The first section has a first density, the cellulosic microstructure within the first section has a first lumen defined by a first cell wall, the first lumen has a first average cross-sectional dimension, and the first cell wall has a first average thickness. The second section has a second density, the cellulosic microstructure within the second section has a second lumen defined by a second cell wall, the second lumen has a second average cross-sectional dimension, and the second cell wall has a second average thickness. The second density is greater than the first density, the first average cross-sectional dimension is greater than the second average cross-sectional dimension, the first average thickness is less than the second average thickness, or Any combination of these materials.

[0138] [Note 19] Materials described in any of the appendices or examples of this specification, particularly materials described in any one of appendices 1 to 18, wherein the cellulosic microstructure has lumens defined by cell walls, the lumens extending along the longitudinal growth direction of the natural wood, and the cellulose nanofibers forming the cell walls extending substantially perpendicular to the longitudinal and radial growth directions of the natural wood.

[0139] [Note 20] A material described in any appendix or example of this specification, particularly the material described in Appendix 19, wherein the tensile strength substantially along the radial direction of a continuous block of wood is at least three times that of wood in its natural state.

[0140] [Note 21] A material described in any of the appendices or examples of this specification, particularly the material described in appendice 19 or 20, wherein the tensile strength substantially along the radial direction of a continuous block of wood is at least 20 MPa.

[0141] [Note 22] A material described in any of the appendices or examples of this specification, particularly a material described in any one of appendices 19 to 21, wherein the tensile strength substantially along the longitudinal growth direction of a continuous block of wood is at least 60 MPa.

[0142] [Note 23] A material described in any of the appendices or examples of this specification, particularly a material described in any one of appendices 19 to 22, wherein the tensile strength substantially along the longitudinal growth direction of a continuous block of wood is at least 80 MPa.

[0143] [Note 24] A material as described in either the appendix or example of this specification, particularly the material as described in Appendix 1, wherein the lignin properties include the chromophore state of the lignin, the chromophore state in the first section is modified from the chromophore state of wood in its natural state, and the lignin in the second section retains the chromophore state of wood in its natural state.

[0144] [Note 25] Materials described in any appendix or example of this specification, particularly the material described in Appendix 24, wherein the altered chromophore state includes the removal of the chromophore from lignin via oxidation.

[0145] [Note 26] A material described in any of the appendices or examples of this specification, particularly the material described in appendice 24 or 25, wherein the wood in its natural state is hardwood or softwood.

[0146] [Note 27] A material described in any of the appendices or examples of this specification, particularly a material described in any one of appendices 24 to 26, wherein a first section is substantially transparent to some or all wavelengths in the visible light spectrum (e.g., 380 nm to 750 nm), and a second section is opaque to some or all wavelengths in the visible light spectrum (e.g., 380 nm to 750 nm).

[0147] [Note 28] A material described in any of the appendices or examples of this specification, particularly a material described in any one of appendices 24 to 27, wherein a first section has a transmittance of at least 85% to light having a wavelength of 600 nm, a first section has a transmittance of at least 80% to some or all wavelengths in the visible light spectrum (e.g., 380 nm to 750 nm), a second section has a transmittance of 60% or less to some or all wavelengths in the visible light spectrum (e.g., 380 nm to 750 nm), a second section has a transmittance of 50% or less to light having a wavelength of 600 nm, or any combination thereof.

[0148] [Note 29] A material described in any of the appendices or examples of this specification, particularly a material described in any one of appendices 24 to 28, wherein the first section is a material having a transmittance of 90% or more for some or all of the wavelengths in the range of 400 nm to 800 nm (inclusive).

[0149] [Note 30] A material described in any of the appendices or examples of this specification, in particular a material described in any one of appendices 24 to 29, wherein both the first section and the second section have at least 70% of the lignin of wood in its natural state.

[0150] [Note 31] Materials described in any of the appendices or examples of this specification, particularly materials described in any one of appendices 24 to 30, wherein the lignin content in the second section is greater than the lignin content in the first section.

[0151] [Note 32] A material as described in any of the appendices or examples of this specification, particularly a material as described in any one of appendices 24 to 31, wherein the lignin content of the first section, the lignin content of the second section, or the lignin content of both the first and second sections is at least 15 wt%.

[0152] [Note 33] Materials described in any of the appendices or examples of this specification, particularly materials described in any one of appendices 24 to 32, wherein the first and second sections are materials from which 30% or less of the natural lignin of the wood has been removed by chemical modification.

[0153] [Note 34] A material described in any of the appendices or examples of this specification, particularly a material described in any one of appendices 24 to 33, wherein a continuous block of wood has a transmittance of 20% or less for some or all of the wavelengths in the range of 200 nm to 350 nm (including both ends).

[0154] [Note 35] A material described in any of the appendices or examples of this specification, particularly a material described in any one of appendices 24 to 34, wherein a continuous block of wood has an absorption rate of at least 80% for some or all of the wavelengths of light in the range of 200 nm to 350 nm (inclusive).

[0155] [Note 36] A material described in any of the appendices or examples of this specification, particularly a material described in any one of appendices 24 to 35, wherein a continuous block of wood exhibits at least 50% haze to light having a wavelength of 600 nm.

[0156] [Note 37] A material described in any of the appendices or examples of this specification, particularly a material described in any one of appendices 24 to 36, wherein a continuous block of wood exhibits at least 60% haze for some or all of the wavelengths of light in the range of 400 nm to 800 nm (inclusive), or a continuous block of wood exhibits at least 65% haze for some or all of the wavelengths of light in the range of 400 nm to 800 nm (inclusive).

[0157] [Note 38] A material described in any of the appendices or examples of this specification, in particular a material described in any one of appendices 24 to 37, wherein the first and second sections have a predetermined pattern independent of the cellulosic microstructure beneath the natural wood.

[0158] [Note 39] Materials described in any of the appendices or examples of this specification, particularly those described in any one of appendices 24 to 38, wherein the cellulosic microstructure has a lumen defined by a cell wall, the lumen extends along the longitudinal growth direction of the natural wood, and the cellulose nanofibers forming the cell wall extend substantially perpendicular to the longitudinal and radial growth directions of the natural wood. [Note 40] Materials described in either the appendix or example of this specification, in particular the material described in appendix 39, The tensile strength substantially along the radial direction of a continuous block of wood is at least 40 times that of wood in its natural state. The tensile strength of a continuous block of wood substantially along the longitudinal growth direction is at least 1.5 times that of wood in its natural state. The tensile strength substantially along the radial direction of a continuous block of wood is at least 25 MPa. The tensile strength substantially along the longitudinal growth direction of a continuous block of wood is at least 40 MPa, or Any combination of these, material [Note 41] A material comprising sections of wood that have been chemically modified so as to alter or remove the chromophore of lignin in the wood in its natural state, The section retains at least 70% of the lignin of the wood in its natural state, and the cellulosic microstructure of the wood in its natural state. material.

[0159] [Note 42] A material described in either the appendix or example of this specification, particularly the material described in Appendix 41, wherein the lignin content of the section is at least 15 wt%.

[0160] [Note 43] A material described in any appendix or example of this specification, particularly the material described in appendix 41 or 42, wherein the section has at least 80% of the lignin of wood in its natural state.

[0161] [Note 44] Materials described in any of the appendices or examples of this specification, in particular the materials described in any one of appendices 41 to 43, Each of the three orthogonal dimensions of the section is 0.5 mm or greater. Each of the three orthogonal dimensions of the section is 1 cm or more. At least two of the three orthogonal dimensions of the section are 10 cm or more. At least one of the three orthogonal dimensions of the section is 20 cm or more, or Any combination of these, material.

[0162] [Note 45] Materials described in any of the appendices or examples of this specification, in particular the materials described in any one of appendices 41 to 44, wherein the section includes an entire continuous block of wood.

[0163] [Note 46] Materials described in any of the appendices or examples of this specification, in particular the materials described in any one of appendices 41 to 44, The section includes the first section of a continuous block of wood, The materials include a second section of continuous wooden blocks adjacent to the first section, The lignin in the second section maintains the chromophore state of the wood in its natural state. material.

[0164] [Note 47] A material described in any of the appendices or examples of this specification, particularly the material described in appendice 45 or 46, wherein the continuous wood blocks are essentially made of wood.

[0165] [Note 48] Materials described in any of the appendices or examples of this specification, particularly the materials described in any one of appendices 41 to 47, wherein the section has a reflectance of 90% or more to some or all of the wavelengths of light in the range of 400 nm to 800 nm (inclusive), [Note 49] Materials described in any of the appendices or examples of this specification, particularly the materials described in any one of appendices 41 to 48, wherein the section is substantially white.

[0166] [Note 50] A material described in any of the appendices or examples of this specification, particularly a material described in any one of appendices 41 to 48, wherein the section further comprises a polymer that penetrates a cellulosic microstructure, the polymer having a refractive index substantially matching that of cellulose, filling empty spaces in the microstructure, and the section being substantially transparent to light having a wavelength of 600 nm.

[0167] [Note 51] A material described in any appendix or example of this specification, particularly the material described in Appendix 50, wherein the section is substantially transparent to some or all wavelengths in the visible light spectrum (e.g., 380 nm to 750 nm).

[0168] [Note 52] Materials described in either the appendices or examples of this specification, particularly the materials described in appendice 50 or 51, the section of which is: Transmittance of at least 80% for light with a wavelength of 600 nm, Transmittance of 90% or more for some or all of the wavelengths of light in the range of 400nm to 800nm ​​(including both ends), A transmittance of 20% or less for some or all of the wavelengths of light in the range of 200nm to 350nm (including both ends), Absorption rate of at least 80% for some or all of the wavelengths of light in the range of 200nm to 350nm (including both ends), For light with a wavelength of 600 nm, at least 65% haze, For some or all of the wavelengths of light in the range of 400nm to 800nm ​​(including both ends), there is at least 50% (e.g., at least 60% or at least 65%) haze, Any combination of these, material.

[0169] [Note 53] Materials described in any of the appendices or examples of this specification, in particular the materials described in any one of appendices 50 to 52, wherein the section comprises essentially wood and a penetrating polymer.

[0170] [Note 54] A step of subjecting a continuous block of wood to a first-time chemical treatment to remove lignin from a first section and a second section within the continuous block of wood, while substantially preserving the cellulosic microstructure of the wood, wherein the first section is adjacent to the second section, and the first time is selected such that at least 90% of the lignin of the wood in the first section is removed and 75% or less (e.g., 65% or less, or 50% or less) of the lignin in the second section is removed. The steps include impregnating a continuous block of wood with a polymer to fill the empty spaces within the retained cellulosic microstructure of the first and second sections, wherein the polymer has a refractive index substantially matching that of cellulose, and A method including, After the penetration step, the first section is substantially transparent to light with a wavelength of 600 nm, and the second section is semi-transparent to light with a wavelength of 600 nm. method.

[0171] [Note 55] A method according to any of the appendices or examples described herein, particularly the method according to appendice 54, wherein the wood is a softwood.

[0172] [Note 56] A method according to any of the appendices or examples described herein, particularly the method according to appendice 54 or 55, wherein, after the penetration step, the first section has a transmittance of at least 85% for light having a wavelength of 600 nm, the first section has a transmittance of at least 80% for some or all wavelengths in the visible light spectrum (e.g., 380 nm to 750 nm), the second section has a transmittance of 70% or less for some or all wavelengths in the visible light spectrum (e.g., 380 nm to 750 nm), the second section has a transmittance of 60% or less for light having a wavelength of 600 nm, or any combination thereof.

[0173] [Note 57] A method according to any of the appendices or examples described herein, particularly the method according to any one of appendices 54 to 56, wherein, after the steps of providing, the lignin content of the first section is 3 wt% or less.

[0174] [Note 58] A method according to any of the appendices or examples described herein, particularly the method according to any one of appendices 54 to 57, wherein, after the steps provided, the lignin content of the first section is 1 wt% or less.

[0175] [Note 59] A method according to any of the appendices or examples described herein, particularly the method according to any one of appendices 54 to 58, wherein, after the steps provided, the lignin content of the second section is 7.5 wt% or more.

[0176] [Note 60] A method according to any of the appendices or examples described herein, particularly the method according to any one of appendices 54 to 59, wherein, after the steps provided, the lignin content of the second section is 12.5 wt% or more.

[0177] [Note 61] A method according to any of the appendices or examples described herein, particularly a method according to any one of appendices 54 to 60, wherein the first section corresponds to the earlywood region of natural wood, and the second section corresponds to the latewood region of natural wood.

[0178] [Note 62] A method according to any of the appendices or examples described herein, particularly the method according to any one of appendices 54 to 61, wherein the chemical treatment comprises a solution of sodium chlorite (NaClO2).

[0179] [Note 63] A method according to any of the appendices or examples described herein, particularly the method according to any one of appendices 54 to 62, wherein the chemical treatment comprises a solution of sodium chlorite (NaClO2) and acetic acid.

[0180] [Note 64] A method according to any of the appendices or examples described herein, particularly the method according to appendice 63, wherein the solution is boiled while being provided.

[0181] [Note 65] A method according to any of the appendices or examples described herein, in particular the method according to any one of appendices 54 to 64, wherein the first time is less than 5 hours or substantially equal to 5 hours.

[0182] [Note 66] A method according to any of the appendices or examples described herein, in particular the method according to any one of appendices 54 to 65, wherein the first time is 2 hours or less.

[0183] [Note 67] A method according to any of the appendices or examples described herein, in particular the method according to any one of appendices 54 to 66, wherein the penetration step is: The steps include immersing a series of wooden blocks in a liquid polymer or polymer precursor, The steps include applying a vacuum to flow a liquid polymer or polymer precursor into a cellulosic microstructure, The process involves drying a liquid polymer or polymerizing a precursor to form a solid polymer in situ within the microstructure of a continuous block of wood, Methods that include...

[0184] [Note 68] A method according to any of the appendices or examples described herein, in particular the method according to Appendix 67, wherein the infiltration step further comprises the step of pressing a continuous block of wood during drying or polymerization.

[0185] [Note 69] A method according to any of the appendices or examples described herein, particularly the method according to any one of appendices 54 to 68, wherein the polymer comprises an epoxy resin.

[0186] [Note 70] The steps include applying a first amount of liquid oxidizing agent to the outer surface of a continuous section of wood blocks, The process involves, during or after the coating step, exposing a continuous section of wood blocks to ultraviolet (UV) light, A method including, The lignin chromophore within the section is chemically oxidized and removed in situ by UV exposure in the presence of a liquid oxidizing agent. After the exposure step, at least 70% of the cellulosic microstructure of the wood and the lignin in the section prior to the coating step are retained. method.

[0187] [Note 71] A method according to any of the appendices or examples described herein, particularly the method according to appendice 70, wherein the liquid oxidizing agent comprises a solution of hydrogen peroxide (H2O2).

[0188] [Note 72] A method according to any of the appendices or examples described herein, particularly the method according to appendice 71, wherein the concentration of hydrogen peroxide in the solution is at least 30 wt%.

[0189] [Note 73] A method according to any of the appendices or examples described herein, particularly the method according to any one of appendices 70 to 72, wherein, after the exposure step, the lignin content of the section is at least 15 wt%.

[0190] [Note 74] A method according to any of the appendices or examples described herein, particularly the method according to any one of appendices 70 to 73, wherein the outer surface of the section has a surface area, and the first amount is at least 800 ml / m² of the surface area. 2 The method.

[0191] [Note 75] A method according to any of the appendices or examples described herein, particularly the method according to any one of appendices 70 to 74, wherein the section has thickness in a direction perpendicular to the outer surface, and the first amount is at least 125 ml per square meter of surface area per 0.1 mm thickness.

[0192] [Note 76] A method according to any of the appendices or examples described herein, in particular the method according to any one of appendices 70 to 75, wherein the first amount is less than 1.5 times the volume of the section, or the first amount is in the range of 1 to 5 times (inclusive).

[0193] [Note 77] A method according to any of the appendices or examples described herein, in particular the method according to any one of appendices 70 to 76, comprising the step of applying a second amount of alkali to the outer surface of a continuous section of wood block before or simultaneously with the coating step.

[0194] [Note 78] A method according to any of the appendices or examples described herein, particularly the method according to appendice 77, wherein the second amount is 20% or less of the first amount.

[0195] [Note 79] A method according to any of the appendices or examples described herein, particularly the method according to appendice 77 or 78, wherein the second amount is 3 ml or less.

[0196] [Note 80] A method according to any of the appendices or examples described herein, particularly the method according to any one of appendices 77 to 79, wherein the alkali comprises sodium hydroxide (NaOH), potassium hydroxide (KOH), ammonium hydroxide (NH4OH), calcium hydroxide (Ca(OH)2), or any combination thereof.

[0197] [Note 81] A method according to any of the appendices or examples described herein, particularly the method according to any one of appendices 77 to 80, wherein the concentration of alkali in the solution is at least 10 wt%.

[0198] [Note 82] A method according to any of the appendices or examples described herein, in particular the method according to any one of appendices 70 to 81, wherein the coating step comprises immersing a series of wood blocks in a first amount of liquid oxidizing agent.

[0199] [Note 83] A method described in any of the appendices or examples described in this specification, particularly the method described in any one of Appendices 70 to 81, wherein the coating step includes direct coating on the outer surface without immersing continuous wood blocks.

[0200] [Appendix 84] A method described in any of the appendices or examples described in this specification, particularly the method described in Appendix 83, wherein the coating step includes multiple divided coatings to achieve a first amount.

[0201] [Appendix 85] A method described in any of the appendices or examples described in this specification, particularly the method described in Appendix 83 or 84, wherein the direct coating includes brushing, spraying, rolling, or any combination thereof.

[0202] [Appendix 86] A method described in any of the appendices or examples described in this specification, particularly the method described in any one of Appendices 83 to 85, wherein the coating step includes applying a first amount on the outer surface in a predetermined pattern without applying a liquid oxidant to a second section of continuous wood blocks adjacent to the section.

[0203] [Appendix 87] A method described in any of the appendices or examples described in this specification, particularly the method described in Appendix 86, wherein after the exposure step, the second section has a lignin content greater than the lignin content of the section.

[0204] [Appendix 88] A method described in any of the appendices or examples described in this specification, particularly the method described in Appendix 86 or 87, wherein after the exposure step, the section is substantially white and the second section is non-white.

[0205] [Appendix 89] A method according to any of the appendices or examples described herein, in particular the method according to any one of appendices 86 to 88, further comprising the step of placing a hydrophobic material on the outer surface to define the boundaries of a predetermined pattern before the coating step.

[0206] [Note 90] A method according to any of the appendices or examples described herein, particularly the method according to appendice 89, wherein the hydrophobic material comprises petrolatum.

[0207] [Note 91] A method according to any of the appendices or examples described herein, in particular the method according to any one of appendices 70 to 90, wherein the exposure step includes irradiating a section using a mask having a predetermined pattern, without irradiating a second section of a continuous block of wood adjacent to the section.

[0208] [Note 92] A method according to any of the appendices or examples described herein, in particular the method according to appendice 91, wherein, after the exposure step, the second section has a lignin content greater than the lignin content of the section.

[0209] [Note 93] A method according to any of the appendices or examples described herein, particularly the method according to appendice 91 or 92, wherein after the exposure step, the section is substantially white and the second section is not white.

[0210] [Note 94] A method described in any of the appendices or examples described herein, in particular a method described in any one of appendices 70 to 93, The step of impregnating a continuous block of wood with a polymer after the exposure step to fill the empty spaces in the retained cellulosic microstructure of the section, wherein the polymer has a refractive index substantially matching that of cellulose. It further includes, After the penetration step, the section is substantially transparent to light having a wavelength of 600 nm. method.

[0211] [Note 95] A method according to any of the appendices or examples described herein, in particular the method according to appendice 94, wherein the penetration step is: The steps include immersing a series of wooden blocks in a liquid polymer or polymer precursor, The steps include applying a vacuum to flow a liquid polymer or polymer precursor into a cellulosic microstructure, The process involves drying a liquid polymer or polymerizing a precursor to form a solid polymer in situ within the microstructure of a continuous block of wood, Methods that include...

[0212] [Note 96] A method according to any of the appendices or examples described herein, particularly the method according to appendices 94-95, wherein the polymer comprises an epoxy resin.

[0213] [Note 97] A method according to any of the appendices or examples described herein, in particular the method according to any one of appendices 94 to 96, wherein after the infiltration step, the section is: Transmittance of at least 90% for light with a wavelength of 600 nm, Transmittance of at least 80% for some or all of the wavelengths of light in the range of 400nm to 800nm ​​(including both ends), Transmittance of at least 90% for some or all of the wavelengths of light in the range of 400nm to 800nm ​​(including both ends), Transmittance of at least 80% for some or all wavelengths of light, A transmittance of 20% or less for some or all of the wavelengths of light in the range of 200nm to 350nm (including both ends), Absorption rate of at least 80% for some or all of the wavelengths of light in the range of 200nm to 350nm (including both ends), At least 50% haze for light having a wavelength of 600 nm, At least 65% haze for some or all of the wavelengths of light in the range of 400 nm to 800 nm (including both ends), or Including any combination of these, Method.

[0214] [Appendix 98] The method described in any of the appendices or examples described in this specification, particularly the method described in any one of Appendices 70 to 97, wherein the UV irradiation is from an artificial light source that generates at least 20 W of UVA band radiation. Method.

[0215] [Appendix 99] The method described in any of the appendices or examples described in this specification, particularly the method described in any one of Appendices 70 to 97, wherein the UV irradiation is sunlight at a UV index (UVI) of at least 5. Method.

[0216] [Appendix 100] The method described in any of the appendices or examples described in this specification, particularly the method described in any one of Appendices 70 to 99, wherein the exposure time is 2 hours or less. Method.

[0217] [Appendix 101] The method described in any of the appendices or examples described in this specification, particularly the method described in any one of Appendices 70 to 99, wherein the exposure time is 1 hour or less. Method.

[0218] [Appendix 102] (a) A step of oxidizing a section of a continuous wood block with a photocatalyst to chemically modify the natural lignin in the section in situ and removing its chromophore while maintaining its bulk aromatic skeleton, Method.

[0219] [Appendix 103] The method described in any of the appendices or examples described in this specification, particularly the method described in Appendix 102, Prior to (a), the section has a first lignin content, (a) After the section, the section has a second lignin content, The second content is at least 70% of the first content. Prior to (a), the section has a first lignin content, (a) After the section, the section has a second lignin content, The second content is at least 70% of the first content. method.

[0220] [Note 104] A method according to any of the appendices or examples described herein, particularly the method according to appendice 103, wherein the second lignin content is at least 15 wt%.

[0221] [Note 105] A method according to any of the appendices or examples described herein, in particular a method according to any one of appendices 102 to 104, wherein, after (a), the section becomes substantially white.

[0222] [Note 106] A method according to any of the appendices or examples described herein, in particular the method according to any one of appendices 102 to 105, wherein, following (a), the section has a reflectance of at least 85% for light having wavelengths in the range of 400 nm to 800 nm (inclusive).

[0223] [Note 107] A method described in any of the appendices or examples described herein, in particular a method described in any one of appendices 102 to 106, (b) Following (a), a step of impregnating a continuous block of wood with a refractive index matching polymer to make the section substantially transparent. Methods that further include the above.

[0224] [Note 108] The method described in any of the appendices or examples in this specification, in particular the method described in Appendix 107, wherein after (b), The section has a transmittance of at least 85% for some or all of the wavelengths of light in the range of 400nm to 800nm ​​(including both ends), or The section has at least 65% haze corresponding to some or all of the wavelengths of light in the range of 400nm to 800nm ​​(including both ends), or It is both of these. method.

[0225] [Note 109] A method according to any of the appendices or examples described herein, in particular the method according to any one of appendices 102 to 108, wherein photocatalytic oxidation comprises a combination of hydrogen peroxide and ultraviolet irradiation.

[0226] [Note 110] A method according to any of the appendices or examples described herein, particularly the method according to appendice 109, wherein hydrogen peroxide is applied to the outer surface of a section without immersion of a continuous block of wood in a solution.

[0227] [Note 111] A method according to any of the appendices or examples described herein, in particular a method according to any one of appendices 102 to 110, wherein (a) in which another section of a continuous block of wood is not subjected to photocatalytic oxidation, and the sections and other sections constitute a predetermined pattern.

[0228] [Note 112] A method according to any of the appendices or examples described herein, in particular the method according to Appendix 111, wherein (a) one of hydrogen peroxide and ultraviolet light is applied to another section.

[0229] [Note 113] Materials described in any of the appendices or examples described herein, in particular the materials described in any one of appendices 54 to 112.

[0230] [Note 114] Materials described in any of the appendices or examples of this specification, particularly those described in any one of appendices 1 to 53 and 113, which are adapted for use as building or structural materials.

[0231] [Conclusion] The features illustrated or described in Figures 1A to 9I and Appendices 1 to 114 can all be combined with other features illustrated or described in Figures 1A to 9I and Appendices 1 to 114 to provide materials, structures, methods, apparatus, and embodiments not illustrated or specifically described herein. All features described herein are independent of each other and can be used in combination with other features described herein, except where structurally impossible.

[0232] Considering the many possible embodiments to which the principles of the disclosed technology may be applied, it should be noted that the illustrated embodiments are merely preferred examples of the disclosed technology and do not limit the technology described herein. Rather, the scope of the technology of the present invention is defined by the appended claims. Accordingly, the applicant may claim that everything within the scope and spirit of these claims constitutes the present invention.

Claims

1. A material comprising a continuous block of chemically modified wood impregnated with a polymer, Chemically modified wood retains the cellulosic microstructure of wood in its natural state, and the polymer has a refractive index substantially matching that of cellulose, filling the empty spaces within the microstructure. The aforementioned continuous wood block is a single continuous piece of wood taken from a single tree, and has a first section and a second section adjacent to the first section. At least one of the first section and the second section is chemically modified such that the lignin content of the first section is lower than the lignin content of the second section. The first section has a transmittance of at least 85% for light having a wavelength of 600 nm, The second section has a transmittance of 60% or less for light having a wavelength of 600 nm. material.

2. The material according to claim 1, wherein the wood in its natural state is softwood.

3. The material according to claim 1, wherein the transmittance of the second section is 36% or more for light having a wavelength of 600 nm.

4. The material according to claim 1, wherein the first section has 10% or less of the lignin of the wood in its natural state, and the second section has at least 25% of the lignin of the wood in its natural state.

5. The material according to claim 1, wherein the lignin content of the first section is 3 wt% or less, and the lignin content of the second section is 7.5 wt% or more.

6. The material according to claim 1, wherein the lignin content of the first section is 1 wt% or less, and the lignin content of the second section is 12.5 wt% or more.

7. The material according to claim 1, wherein the first section corresponds to the earlywood region of the wood in its natural state, and the second section corresponds to the latewood region of the wood in its natural state.

8. The first section has a first density, the cellulosic microstructure within the first section has a first lumen defined by a first cell wall, the first lumen has a first average cross-sectional dimension, and the first cell wall has a first average thickness. The second section has a second density, the cellulosic microstructure within the second section has a second lumen defined by a second cell wall, the second lumen has a second average cross-sectional dimension, and the second cell wall has a second average thickness. The second density is greater than the first density, the first average cross-sectional dimension is greater than the second average cross-sectional dimension, the first average thickness is smaller than the second average thickness, or Any combination of these, The material according to claim 1.

9. The material according to claim 1, wherein the cellulosic microstructure has a lumen defined by a cell wall, the lumen extends along the longitudinal growth direction of the natural wood, and the cellulose nanofibers forming the cell wall extend along a direction substantially perpendicular to the longitudinal growth direction and radial direction of the natural wood.

10. The material according to claim 9, wherein the tensile strength of the continuous wood block substantially along the radial direction is at least three times that of the wood in its natural state.

11. A step of subjecting a continuous block of wood to a first-time chemical treatment to remove lignin from a first section and a second section within the continuous block of wood while substantially preserving the cellulosic microstructure of the wood, wherein the continuous block of wood is a single continuous piece of wood taken from a single tree, the first section is adjacent to the second section, and the first time is selected such that at least 90% of the lignin in the wood in the first section is removed and 75% or less of the lignin in the second section is removed. The process involves impregnating the continuous wood blocks with a polymer to fill the empty spaces within the retained cellulosic microstructure of the first and second sections, wherein the polymer has a refractive index substantially matching that of cellulose. Includes, After the penetration step, the first section has a transmittance of at least 85% to light having a wavelength of 600 nm, and the second section has a transmittance of 60% or less to light having a wavelength of 600 nm. method.

12. The method according to claim 11, wherein the wood is a softwood.

13. The method according to claim 11, wherein, after the penetration step, the second section has a transmittance of 36% or more for light having a wavelength of 600 nm.

14. The method according to claim 11, wherein, after the step of subjecting to the chemical treatment, the lignin content of the first section is 3 wt% or less, and the lignin content of the second section is 7.5 wt% or more.

15. The method according to claim 11, wherein, after the step of subjecting the section to the chemical treatment, the lignin content of the first section is 1 wt% or less, and the lignin content of the second section is 12.5 wt% or more.

16. The method according to claim 11, wherein the first section corresponds to the earlywood region of the wood in its natural state, and the second section corresponds to the latewood region of the wood in its natural state.

17. The aforementioned chemical treatment involves sodium chlorite (NaClO ２ A solution of ) and acetic acid, or sodium chlorite (NaClO ２ The method according to claim 11, comprising a solution of ).

18. The aforementioned penetration step is, The steps include immersing the aforementioned continuous wood blocks in a liquid polymer or polymer precursor, The steps include applying a vacuum to flow the liquid polymer or polymer precursor into the cellulosic microstructure, The steps include drying the liquid polymer or polymerizing the precursor to form a solid polymer in situ within the microstructure of the continuous wood block, The method according to claim 11, including the method described in claim 11.

19. The method according to claim 18, wherein the impregnation step further comprises the step of pressing the continuous wood blocks during the drying or polymerization.

20. The method according to claim 11, wherein the polymer includes an epoxy resin.

Images