Systems and methods for low-emissivity and / or thermally insulating formulations

Abstract

Systems and methods for controlling the temperature of a subject, including a spreadable formulation to coat a tissue surface, comprising a fluid-based carrier, and a thermal control material contacting the fluid-based carrier, wherein the thermal control material is configured to control one or more of radiative heating, conductive heating, convective heating, radiative cooling, conductive cooling, or convective cooling.

Description

Atty. Dkt. No. 125141.04952.MGH2025-112-02SYSTEMS AND METHODS FOR LOW-EMISSIVITY AND / OR THERMALLY INSULATING FORMULATIONSCross Reference to Related Applications

[0001] The present application is based on, claims priority to, and incorporates herein by reference in its entirety for all purposes, US Provisional Application Serial No. 63 / 752,038, fded January 31, 2025.Statement of Government Support

[0002] This invention was made with government support under FA9550-23-1-0656 awarded by the Air Force Office of Scientific Research. The government has certain rights in the invention.Background

[0003] Electromagnetic radiation is emitted by all matter at temperatures above OK (absolute zero). The amount and the wavelength distribution of this emitted energy is determined by an object's temperature, and by its emissivity. In classical physics, an object at thermal equilibrium in a vacuum (that is, having no heat loss or gain by conduction or convection) must be at thermal equilibrium with its environment by absorbing and emitting the same amount of radiation. An ideal black body is an object that absorbs all radiation at all wavelengths, and is also the ideal emitter of radiation. Emission of energy due to an object's temperature is therefore called blackbody radiation. At a fundamental level, blackbody radiation equates the ability of an object to emit, with the ability of the same object to absorb any given wavelength. Mathematically, for an object for which transmission (T) =0, A(absorptivity) = E(emissivity), at any given wavelength. A and E vary between 0 and 1. At any given wavelength, the perfect black body has A=E=1, and the perfect reflective body has A=E=0. The wavelength distribution of blackbody radiation emitted by an object depends on its temperature.

[0004] Blackbody radiation has its maximum intensity at a wavelength that varies inversely with the object's temperature. Specifically, the maximum wavelength (in micrometers) ~ 3000 / T(°K). This is known as the Wien displacement law. For example, the sun's emission maximum is approximately 0.5 micrometers (500nm) because surface temperature of the sun is about 6000 °K. The human body is normally at a temperature of about 300 - 310 °K. Human skin emission is concentrated in the mid-infrared, including wavelengths in the range of approximately 3-40Atty. Dkt. No. 125141.04952.MGH2025-112-02pm, with a peak near 9-10 pm. Human skin is close to an ideal blackbody, with A=E ~ 0.96. Human skin loses heat by a combination of blackbody emission (radiative cooling), and conduction / convection (cooling by contact). Depending on the particular environment, radiative heat losses can be up to 75% or more of total thermal losses (e.g. in an enclosed room at 0 °C with little to no wind).

[0005] Thus, there is a need to develop approaches to mitigate heat transfer to and from the skin when humans are exposed to extreme conditions or suffer from body temperature regulation conditions.Summary

[0006] The present disclosure provides systems and methods that overcome the aforementioned drawbacks by providing systems for, including formulations, and methods of applying low-emissivity and / or thermally insulating coatings to the skin. The systems and methods disclosed herein may be configured for and / or utilized to (1) retain body heat, keeping the body warm especially in cold environments or as a result of body temperature regulation conditions (e.g., Raynaud’s disease) (2) stabilize body temperature, reducing heat load when exposed to a hot environment, (3) decrease the ability of infrared imaging to detect the human body, for example in military night-vision and targeting systems, (4) protect the skin against burns, including radiation burns, as well as conductive and convective burns, and more.

[0007] In one aspect of the present disclosure, a system for controlling a temperature of a subject is described. The system comprises a spreadable formulation to coat a tissue surface, comprising a fluid-based carrier, and a thermal control material contacting the fluid-based carrier, wherein the thermal control material is configured to control one or more of radiative heating, conductive heating, convective heating, radiative cooling, conductive cooling, or convective cooling.

[0008] In one aspect of the present disclosure, a method of controlling a temperature of a subject is described. The method comprises applying the spreadable formulation to a tissues surface of the subject.

[0009] These aspects are nonlimiting. Other aspects and features of the systems and methods described herein will be provided below.Atty. Dkt. No. 125141.04952.MGH2025-112-02Brief Description of the Drawings

[0010] The foregoing features of embodiments will be more readily understood by reference to the following detailed description, taken with reference to the accompanying drawings, in which:

[0011] FIG. 1A is a schematic of a thermal control formulation, according to aspects of the present disclosure.

[0012] FIG. IB is a schematic of a thermal control formulation, according to aspects of the present disclosure.

[0013] FIG. 1C is a schematic of a thermal control formulation, according to aspects of the present disclosure.

[0014] FIG. ID is a schematic of a thermal control formulation, according to aspects of the present disclosure.

[0015] FIG. 2A is a top view of a thermal control material pattern, according to aspects of the present disclosure.

[0016] FIG. 2B shows top views of a thermal control material patterns, according to aspects of the present disclosure.

[0017] FIG. 2C shows top views of a thermal control material patterns, according to aspects of the present disclosure.

[0018] FIG. 3 shows scanning electron microscopy (SEM) images of silver nanowires randomly arranged at different concentrations.

[0019] FIG. 4 shows results of excised swine skin with (right) and without (left) a low-E formulation comprising a gold leaf coating placed 30 cm beneath a radiative heat source of ~700°C.

[0020] FIG. 5A shows plots of surface temperature for skin coated with (left) and without (right) a low-E coating and various conductive insulation coatings compared to exposed skin in cold temperatures and with high wind, according to aspects of the present disclosure.

[0021] FIG. 5B shows plots of surface temperature for skin coated with (left) and without (right) a low-E coating and various conductive insulation coatings compared to exposed skin in cold temperatures and still air, according to aspects of the present disclosure.

[0022] FIG. 5C shows plots of surface temperature for skin coated with (left) and without (right) a low-E coating and various conductive insulation coatings compared to exposed skin in freezing water, according to aspects of the present disclosure.Atty. Dkt. No. 125141.04952.MGH2025-112-02

[0023] FIG. 5D shows a plot of surface temperature for skin coated with various conductive insulation coating compared to a neoprene wetsuit without a low-E formulation coating and exposed skin in freezing water, according to aspects of the present disclosure.

[0024] FIG. 6 is a plot showing radiation protection of skin exposed to a hot radiative source (approximately 700 °C).

[0025] FIG. 7 shows skin sections coated (right) or uncoated (left) with a thermal insulation formulation contacted with a 100°C iron applied with a force of 0.7N for 5 seconds.

[0026] FIG. 8 shows skin sections with coated various thermal insulation formulations contacted with a 100°C iron applied with a force of 0.7N for 5 seconds.Detailed Description

[0027] The systems, including formulations, and methods described herein can be used to limit blackbody radiation emission from the skin, limit convective heat losses from the skin, or otherwise protect skin and / or other tissue against extreme conditions. By applying formulations to the skin that are insulating against convective and conductive heat losses and / or that have high reflectance within the infrared spectrum, especially in the spectral range for blackbody emission from human skin (about 5-30 pm wavelength), the skin and underlying tissue can be protected from undesired conditions. Specifically, less than 1% of emission from human skin occurs under 3 pm, 25% of emission (at regular body temperature) occurs below 9.35 pm, 50% occurs below 13.25 pm, 75% occurs below 19.8 pm, 90% occurs below 30.24 pm, and 99% occurs below 73.6 pm. The "bulk" of emission is centered around the maximum, which is 9.35 - 9.45 pm. When applied to exposed skin, the formulation may retain body heat in cold environments or prevent body heating in hot environments. The formulations may also limit radiation heat exchange and / or convective and conductive exchange, both to and from the environment. In a non-limiting example, by limiting radiation exchange with the environment, skin may be protected from thermal radiation bums.

[0028] In a typical ambient environment at room temperature with little to no wind, blackbody emission from exposed skin accounts for about 50 - 75% of body heat loss. The formulations described herein provide several non-limiting benefits at various temperature ranges. For example, at mild temperatures, the formulations may lead to reduced heating or assuage symptoms of individuals suffering from body temperature regulation conditions.Atty. Dkt. No. 125141.04952.MGH2025-112-02

[0029] FIGS. 1 A-1D are cross-sectional views of non-limiting example formulations, according to present disclosure. The systems, including spreadable formulations, for application on tissue surface 100 (e.g., skin) can include a fluid-based carrier 105 that is spreadable to coat the tissue surface 100, and athermal control material 110 contacting the fluid-based carrier 105. The thermal control material 110 may be configured to control one or more of radiative heating, conductive heating, convective heating, radiative cooling, conductive cooling, or convective cooling. Moreover, the thermal control material 110 may be one or more of a low-emissivity (low-E) material, for controlling radiative cooling and radiative heating, or a thermal insulation material to control one or more of conductive or convective cooling. FIGS. 1 A-1C depict the thermal control material as particles disposed within the fluid-based carrier 105 homogeneously (FIG. 1A), along a concentration gradient along an axis (FIG. IB), and concentrated along a plane of the fluid based-carrier 105 (FIG. 1C). These example distribution patterns are nonlimiting. Alternatively, the thermal control material 110 is not limited to uniform particles, and may also be irregular particles, flakes, one or more wires, one or more fdaments, or the like. FIG. ID illustrates an example formulation where the thermal control material 110 is arranged as a sheet contacting a surface of the fluid-based carrier 105. As depicted, the thermal control material 110 sheet sits atop the upper surface of the fluid-based carrier 105 opposite the bottom surface in contact with the tissue surface 100.

[0030] In a non-limiting example, the formulation may be premixed in the case of FIGS. 1A-1C and applied directly onto the tissue surface 100. Alternatively, the formulation may be formed in situ, by first applying the fluid-based carrier 105 followed by application of the thermal control material 110 on the upper surface of the fluid-based carrier 105. In another example, the formulation may be applied as a mixture of the carrier 105 and the thermal control material 110 that self-separates into one or more layers based on physical properties of the components such as density, electrostatic charge, surface charge and / or immiscibility. Moreover, the thermal material 110 may self-separate in any order relative to the surface of the skin. The formulations may be applied in individual layers, or as layered composites. In some embodiments, the thermal control material may carry a net positive charge or may be surface functionalized to exhibit a selected charge, such that the thermal control material preferentially localizes above, below or at an interface within the carrier.Atty. Dkt. No. 125141.04952.MGH2025-112-02

[0031] In a non-limiting example, the fluid-based carrier 105 may be a cream, lotion, ointment, film-forming agents, or any other topically applied formulation. As used herein, “creams” refer to mixtures of aqueous and non-aqueous components, including oil-in water (cold creams) and water-in-oil (standard creams) mixtures. As used herein, “lotions” refer to mixtures of aqueous and non-aqueous components with higher water contents than creams. As used herein, “ointments” refer to hydrophobic formulations based on oils, petrolatum, waxes, and the like.

[0032] In some embodiments, the carrier 105 comprises a self-expanding material that forms a porous or cellular structure upon application, such that expansion of the carrier traps air within the structure and there by reduces conductive and convective heat transfer. The self-expanding material may comprise a foam, aerated polymer or expandable matrix that increases in volume after application to the skin or substrate. The porous structure may comprise open cell or closed cell regions and, in some embodiments, includes voids containing air, low thermal conductivity gases, or gases at reduced pressure.

[0033] In another example, the carrier 105 may comprise a cream, gel or fluid formulation containing heat activated, chemically activated or mechanically activated expanding materials that expand after application to form an insulating layer. Upon expansion, the carrier increases its effective thickness and air content thereby enhancing thermal insulation.

[0034] In a non-limiting example, the fluid-based carrier may further include components comprising any one of the ingredients on the Generally Regarded As Safe (GRAS) list for skin applications approved by the Federal Drug Administration (FDA). However, the fluid-based formulation is not limited thereto, and may include any ingredients one of skill in the art would find suitable for topical skin applications. In a non-limiting example, the formulations are further devoid of irritants, toxins, pathogens, and allergens.

[0035] These components may be disposed in the fluid-based carrier 105 in effective amounts to adjust one or more of an appearance, flowability, viscosity, adhesion, elasticity, thickness, odor, aqueous solubility, permeability, temperature resistance, durability, or the like based on the target environment and wearer’s need. For example, the formulation may have low water solubility for use in aqueous environments (e.g., swimming, inclement weather, etc.). In another example the formulation may be permeable to water vapor such that sweat can evaporate off the tissue surface. In yet another example, the appearance can include the inclusion of dyes or pigments to mimic normal skin color and appearance or to change the appearance such as forAtty. Dkt. No. 125141.04952.MGH2025-112-02camouflage. In another example, the formulation may have sufficient durability or substantivity such that the formulation remains on the skin during normal abrasion, movement, sweating, or general wear. The elasticity may also be controlled such that formulation does not fail mechanically when the underlying skin moves or stretches.

[0036] Furthermore, the components may include, but are not limited to, one or more surfactants, humectants, emollients, occlusives, antioxidants, preservatives, stabilizers, emulsifiers, thickeners, polymers, fragrances, or pigments.

[0037] In a non-limiting example, the fluid-based carrier 105 may include one or more of polysiloxane (or derivatives thereof) or acrylates (or derivates thereof). For example, the fluidbased carrier 105 may include a mixture of acrylate terpolymer (film forming agent), isooctane (solvent for dispersion and rapid drying), hexamethyldisiloxane (quickly evaporating solvent), and polymethylsiloxane copolymer (plasticizer and emollient).

[0038] In a non-limiting example, components of the formulation may be intentionally volatile, such as alcohols, some solvents, or water. Upon evaporation, loss of these volatile components can concentrate the remaining components and thermal materials on the tissue surface.

[0039] In a non-limiting example, the fluid-based carrier 105 may be commonly available products such as sunscreens, moisturizers, cosmetics, or the like.

[0040] Radiative Control

[0041] As mentioned previously, the thermal control material 110 may include low-E materials for controlling radiative heating or radiative cooling. The thermal control materials 110 may be provided in the fluid-based carrier 105 at a quantity necessary to achieve an emissivity of less than 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3. 0.2, 0.1, or any value therein. For example, the emissivity may be less than 0.5. Furthermore, the emissivity may be less than 0.2. In a specific example, the low-E materials have lower infrared (IR) emissivity than that of bare skin (about 0.96). In other words, the low-E formulation coating the tissue surface reduces IR emission from the tissue surface relative to the tissue surface being uncoated or bare. For example, the low-E materials have lower emissivity in the wavelengths ranging from 5-30 pm than that of bare skin. For instance, the low-E materials have lower emissivity at 10 pm than that of bare skin, as this is the approximate wavelength of maximum emission from skin at its normal temperature range.

[0042] In a non-limiting example, the formulations have a total IR reflectance, defined as the sum of specular and diffuse reflectance, greater than 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, orAtty. Dkt. No. 125141.04952.MGH2025-112-02any value therein. When light interacts with a sample, it may be transmitted, reflected, or absorbed, such thatR +A + T = l (1) where R is the reflectance, A is the absorptivity, and T is the transmission. For opaque materials, T=0 and R+A=l. For An object in thermal equilibrium, emissivity is equal to absorptivity, such thatE = AE = 1 - R , (2) for an opaque material. For example, the reflectance may be greater than 0.5. Furthermore, the reflectance may be greater than 0.8.

[0043] The infrared (IR) emissivity of the formulation may be adjusted based on one or more parameters including the intrinsic optical properties of the low-E materials, the physical thickness of the formulation, the concentration of the low-E materials, and the spatial distribution or structural organization of such materials within the formulation. In a given wavelength band, emissivity (s) is governed by the relationship:E = 1 - R - T , (3) where R is reflectance and T is transmission. Accordingly, reduced emissivity may be achieved by increasing reflectance and / or reducing transmission in the relevant wavelength band, while avoiding embodiments in which low transmission is achieved primarily through absorption.

[0044] Low-E materials may include conductive materials, conductive oxides, doped semiconductors, high-refractive-index materials, or combinations thereof. In certain embodiments, the low-E materials may include metals including gold, silver, aluminum, copper, chromium, and alloys thereof. Such metals exhibit high reflectance in the 8-25 pm wavelength band due to free-electron response and associated plasma behavior. When film thickness exceeds several electromagnetic skin depths in the relevant IR band, transmission becomes negligible and emissivity correspondingly decreases. Such films may exhibit predominantly specular reflectance when surface roughness is small relative to the wavelength.

[0045] In other embodiments, the low-E materials may include transparent conductive oxides (TCOs) or degenerately doped semiconductors, including indium tin oxide (ITO), fluorine-doped tin oxide (FTO), aluminum-doped zinc oxide (AZO), antimony-doped tin oxide (ATO), andAtty. Dkt. No. 125141.04952.MGH2025-112-02related materials, may be used. Carrier concentration and plasma frequency may be selected such that reflectance is enhanced in the mid-infrared while substantial visible light transmission is maintained.

[0046] In further embodiments, semiconductor or high-refractive-index materials including Germanium, silicon, and related materials may be used in continuous, particulate, or composite form to enhance infrared reflectance through Fresnel reflection and / or scattering mechanisms.

[0047] The low-E materials may be configured in one or more structural forms including continuous films, multilayer interference stacks, particulate dispersions, flakes, meshes, sheets, filaments, or core-shell structures. In certain embodiments, solid or hollow particles may be coated with a conductive or reflective material to form core-shell structures. For example, glass or polymer microspheres may be coated with silver, aluminum, or other conductive materials and dispersed within a carrier matrix. In a non-limiting example, hollow glass microspheres having diameters of approximately 40 pm may be coated with silver and dispersed within a polysiloxane-based carrier to enhance infrared reflectance while maintaining low density.

[0048] In some embodiments, thin-fdm optical interference structures may be employed.Alternating high-index and low-index dielectric layers may be configured as multilayer stacks to enhance reflectance within a selected infrared wavelength band through constructive interference while permitting transmission of visible light. Layer thickness and refractive index may be selected to achieve wavelength-selective reflectance within the 8-25 pm range.

[0049] In other embodiments, the formulation may comprise diffusely reflective scattering media in which incident infrared radiation undergoes multiple scattering events within a particulate or composite structure. The coating thickness may be selected to be transport-thick in the relevant IR band such that transmission is minimized while absorption remains low. For example, the coating thickness (L) may exceed multiple transport mean free paths (L » 1 / ps'), where ps' is the reduced scattering coefficient in the relevant wavelength range. Under such conditions, incident IR radiation is preferentially redirected outward as diffuse reflectance, thereby reducing effective emissivity of the underlying surface.

[0050] Conductive and / or Convective Control

[0051] In certain embodiments, the thermal control material 110 may further comprise thermally insulating materials configured to reduce conductive heat transfer and to limit convective heat transfer within the material. Non-limiting examples include air-filled glass microshells, hollowAtty. Dkt. No. 125141.04952.MGH2025-112-02microspheres, aerogels, and low-density particles containing gas-filled or partially evacuated internal volumes. As used herein, the term “aerogel” refers to a porous solid material in which a liquid phase of a gel has been replaced with a gas, resulting in extremely low thermal conductivity. Partially evacuated hollow structures, as close to evacuated as possible, reduce heat transfer by suppressing solid conduction and internal gas convection.

[0052] In some embodiments, formulations may comprise both low-E materials and thermally insulating materials. For example, hollow glass microspheres may be dispersed within a polysiloxane-based carrier to reduce conductive heat transfer, while a reflective metallic layer (e.g., gold or silver foil) may be disposed at or near the surface to reduce radiative heat transfer. In this manner, conductive, convective, and radiative heat transfer modes may be addressed simultaneously.

[0053] In certain embodiments, a continuous conductive film or foil may be applied to or embedded within the carrier material. Metallic materials such as gold, silver, aluminum, copper, chromium, and alloys thereof may provide high reflectance in the mid-infrared due to free-electron response and associated plasma behavior. When the thickness of such a film exceeds several electromagnetic skin depths in the relevant infrared band (e.g., 8-25 pm), transmission may become negligible and emissivity correspondingly reduced.

[0054] In other embodiments, the low-E material may be configured as a patterned conductive structure, including but not limited to a mesh, grid, lattice, wire array, perforated film, nanowire network, printed trace pattern, or combinations thereof. Such patterned conductive structures may function as a Faraday-like structure or frequency-selective surface in a target infrared wavelength band.

[0055] Without being bound by theory, when a characteristic opening dimension of the conductive pattern (e.g., gap size, pitch, or aperture width) is smaller than at least a portion of a target infrared wavelength range, transmission of incident infrared radiation may be attenuated and reflection correspondingly enhanced. In certain embodiments, the opening dimensions may be selected to be subwavelength relative to thermal infrared emission wavelengths (e.g., within approximately 8-25 pm, including wavelengths near peak human body emission around 9-10 pm), while remaining sufficiently large relative to visible wavelengths to permit visible light transmission. In this manner, a visibly transparent yet infrared-reflective formulation may be achieved.Atty. Dkt. No. 125141.04952.MGH2025-112-02

[0056] The degree of infrared reflection and transmission suppression in such patterned embodiments may depend on one or more parameters of the thermal control material including: (i) opening geometry and periodicity (regular or irregular), (ii) fill factor and effective surface impedance of the patterned structure, (iii) electrical continuity and percolation of the electrically conductive thermal control material, (iv) conductivity and free-carrier response of the thermal control material at mid-infrared frequencies, (v) thickness of individual electrically conductive thermal control material relative to their electromagnetic skin depth, and (vi) angle of incidence and polarization of the radiation.

[0057] In certain embodiments, the characteristic opening dimension may be less than about one wavelength, less than about one-half wavelength, or less than about one-quarter wavelength of a selected infrared wavelength. In further embodiments, the opening dimension may be substantially smaller than the wavelength (e g., on the order of one-fifth to one-tenth of the wavelength) to further suppress transmission. These ranges are provided as non-limiting examples, and effective infrared reflection may be achieved across a range of subwavelength geometries depending on material properties and structural configuration.

[0058] In grid-based or network embodiments, sufficient electrical continuity may be achieved when the conductive elements exceed a percolation threshold. As used herein, “percolation threshold” refers to the minimum concentration and degree of interconnection required to establish an electrically conductive pathway within the patterned structure. In certain embodiments, relatively low fill factors may be employed while maintaining sufficient electrical continuity and low effective surface impedance to provide meaningful infrared reflection.

[0059] For highly conductive materials such as gold, silver, or copper, effective infrared reflection may additionally depend on the thickness of individual conductive elements relative to electromagnetic skin depth in the relevant wavelength band. In certain embodiments, conductive elements having thicknesses greater than several skin depths may provide enhanced reflection with reduced resistive loss.

[0060] In certain embodiments, the thermal control material may be configured as a multilayer system comprising one or more infrared-reflective layers and one or more thermally insulating layers arranged in stacked, interpenetrating, or spatially distributed configurations. The insulating layer may reduce conductive and internal convective heat transfer, while the low-emissivity layer reduces radiative heat transfer.Atty. Dkt. No. 125141.04952.MGH2025-112-02

[0061] In some embodiments, insulating particles (e.g., hollow glass microspheres, aerogels, or partially evacuated particles) may be dispersed within a carrier matrix, and a reflective film or patterned conductive structure may be disposed at or near an external surface of the formulation. In other embodiments, reflective elements may be embedded within an insulating matrix such that radiative and conductive heat-transfer mechanisms are addressed throughout the thickness of the coating.

[0062] Referring now to FIG. 2A-C, top-views of example patterns are shown for the thermal control material 110 from FIG. ID. However, it is noted that the patterns depicted are not limited to the formulation embodied in FIG. ID.

[0063] FIG. 2A illustrates an area where any of the thermal control materials previously described form a continuous sheet on the fluid-based carrier. For example, low-E gold or silver foil may be applied to the top of the fluid-based carrier.

[0064] FIG. 2B illustrates two regular (uniform) patterns of the thermal control material at a lower grid density (left) and higher grid density (right). In a non-limiting example, the thermal control material is electrically conductive at IR frequencies, and the term “grid density” refers to number and spacing of the electrically conductive thermal control material per unit area. In this example, the grid density of the thermal control material may separately affect the emissivity of the IR emission wavelengths, independent of the emissivity of the thermal control material itself. FIG. 2C alternatively shows two irregular patterns of the thermal control material at a lower grid density (left) and higher grid density (right). Either of these patterns may be formed from an arrangement of particles, wires, filaments, printed traces, perforated sheets, or conductive particle networks.

[0065] FIG. 3 shows SEM images of silver nanowires at 20 mg / mL (top), 5 mg / mL (middle), and 0.1 mg / mL (bottom), illustrating the difference in size in the openings formed in the nanowire networks.

[0066] FIG. 4 illustrates representative experimental results demonstrating reduced radiative heating of excised tissue coated with a gold leaf low-E material compared to uncoated control tissue under exposure to a high-temperature radiative source. Thermocouples positioned superficially and at depth show substantially reduced temperature rise in the coated sample relative to control, consistent with reduced radiative heat transfer.Atty. Dkt. No. 125141.04952.MGH2025-112-02

[0067] The following examples illustrate the relative impact of insulative coatings and low-emissivity coatings in different environments.

[0068] Examples

[0069] Radiative heat losses (heat flux) depend on the difference in fourth power of temperature between the two objects (in this case Tskin and Tenv).where a = 0.97 (emissivity of human skin), and G = 5.67 * IO-8(Stefan Boltzmannconstant).

[0070] Convective heat losses (heat flux) are dependent on the difference in temperature between the two objects> where h is the convective heat transfer coefficient.

[0071] The total heat flux and relative contribution of each of these mechanisms depends on the environment.

[0072] Example 1

[0073] Table 1 provides different scenarios based on skin temperature, wind or water environments, environment temperature, and convective heat transfer coefficient and the effects on radiative heat loss, convective heat loss, and total heat loss.

[0074] Table 1Scenario q”rad q”conv q”totai Rad % Conv % Air: no wind, skin 33°C, air 77 26- 65 103 - 145 54 - 75 25 - 46 20°C, h = 2-5Air: no wind, skin 33°C, air 177 66 - 165 242 - 341 52 - 73 27 - 48 0°C, h = 2-5Air: light breeze, skin 33°C, 177 330 - 990 507-1167 15 - 35 65 - 85 air 0°C, h = 10 - 30Air: strong wind, skin 33°C, 177 990 -3300 1167 - 3478 5 - 15 85 - 95 air 0°C, h = 30 - 100Still water: skin 33°C, water 177 1650 - 16500 1826 - 16676 1 - 10 90- 99 0°C, h = 50 - 500Flowing Water: skin 33 °C, 177 16500- 33000 16677 -330177 0 - 1 99 - 100 water 0°C, h = 500 - 10000Atty. Dkt. No. 125141.04952.MGH2025-112-02

[0075] The relative contribution of radiative and convective heat transfer depends strongly on environmental conditions. In still air, radiative losses may comprise a significant fraction of total heat loss. As convective heat transfer coefficients increase (e.g., wind or flowing water), convective heat transfer increasingly dominates total heat flux.

[0076] Example 2

[0077] Table 2 provides emissivity values of various samples using an emissivity cooling chamber. Carrier l is a commercially available mixture of acrylate terpolymer, isooctane, hexamethyldisiloxane, and polymethylsiloxane copolymer. Carrier 2 is a commercially available body paint binder.Table 2

[0078] Example 3

[0079] The net convective heat flux may be expressed as:^baseline is equal to 1 / h. Additional resistance(s) (Radditionad °faparticular material is directly proportional to its thickness, and inversely proportional to its thermal conductivity.

[0080] For a 200 pm silicone-like layer (k ~ 0.1 W m ' K '):00002

[0081] For a 200 pm silicone / microshell composite (k ~ 0.05 W mLK ’):Atty. Dkt. No. 125141.04952.MGH2025-112-0200002

[0082] For stagnant air (k ~ 0.025 W m ’ K ’):Radditional = 0.008 m2KW1

[0083] Tables 3 and 4 demonstrate that as convective coefficients increase, additional thermal resistance becomes increasingly impactful in reducing total heat flux.

[0084] Aerogel-like layers (k ~ 0.015 W m ’ K ’) and evacuated particle systems (effective k » 0.004 W nr' K-1under idealized conditions) provide substantially greater thermal resistance per unit thickness.Table 3Table 4Atty. Dkt. No. 125141.04952.MGH2025-112-02

[0085] Example 4

[0086] Assuming short-duration exposure, metabolic heat generation and blood perfusion may be neglected, and a thermal reservoir of approximately 33 °C at a depth of 4 mm may be assumed. Under these simplifying assumptions, the following scenarios may be explored.

[0087] FIG. 5A assumes a 200 pm insulating layer having a thermal conductivity ranging from approximately 0.1 W nr' K"1(representative of a silicone fluid-based carrier) to approximately 0.004 W nr’ K-1(representative of a vacuum-like layer), with an outdoor temperature of 0 °C. A low-emissivity coating having emissivity of approximately 0.2 is positioned at the outer surface of the formulation. The convective heat transfer coefficient is taken as 50 W nr2K-1, representing fairly strong wind.

[0088] In the left plot of FIG. 5 A (low-E surface, a ~ 0.2), after approximately 25 seconds of exposure, the surface (0 mm) of exposed skin declines to approximately 26.6 °C. With a silicone-like layer, the surface temperature is approximately 27 °C. For the silicone / microshell mixture, the surface temperature is approximately 27.8 °C. With an aerogel-like coating, the surface temperature is approximately 29 °C.

[0089] In the right plot of FIG. 5 A (higher-emissivity surface, s ~ 0.97), under otherwise identical conditions, the exposed skin surface declines to approximately 26 °C after 25 seconds. With a silicone-like layer, the surface temperature is approximately 27 °C. For the silicone / microshell mixture, the surface temperature is approximately 27.5 °C. With an aerogellike coating, the surface temperature is approximately 29 °C. These results illustrate that under moderate convection, thermal insulation plays a dominant role, although reduced emissivity provides measurable additional benefit.

[0090] FIG. 5B illustrates the same formulations under low convection conditions (h ~ 2 W m"2K"’), representative of indoor still air. In the left plot (low-E surface, s ~ 0.2), after 25 seconds the exposed skin surface declines to approximately 32.5 °C. With a silicone-like layer, the surface temperature is approximately 32.6 °C. For the silicone / microshell mixture, the surface temperature is approximately 32.6 °C. With an aerogel-like coating, the surface temperature is approximately 32.6-32.7 °C.

[0091] In the right plot (higher-emissivity surface, s ~ 0.97), the exposed skin surface declines to approximately 31.9 °C. With the silicone-like layer, the surface temperature is approximately 32 °C. For the silicone / microshell mixture, the surface temperature is approximately 32 °C. With anAtty. Dkt. No. 125141.04952.MGH2025-112-02aerogel-like coating, the surface temperature is approximately 32.1 °C. These results demonstrate that under low convection conditions, reduced emissivity has a comparatively greater impact because radiative heat transfer constitutes a larger fraction of total heat loss.

[0092] FIG. 5C illustrates the same formulations in ice water (T = 0 °C) with a convective heat transfer coefficient of approximately 1000 W m"2K-1. In the left plot (low-E surface, s ~ 0.2), after 25 seconds the exposed skin surface declines to approximately 5 °C. With a silicone-like layer, the surface temperature is approximately 12 °C. For the silicone / microshell mixture, the surface temperature is approximately 16 °C. With an aerogel-like coating, the surface temperature is approximately 25 °C.

[0093] In the right plot (higher-emissivity surface, 8 = 0.97), substantially similar surface temperatures are observed under these high-convection conditions. This indicates that when convective heat transfer dominates (e g., water immersion), radiative heat transfer represents a comparatively small fraction of total heat loss, and thermal insulation thickness and conductivity become the primary determinants of surface temperature. For comparison, a wet neoprene (closed-cell) suit has thermal conductivity of approximately 0.05 W irr' K-1, similar to the silicone / microshell mixture.

[0094] FIG. 5D compares various thermal insulation configurations in 0 °C water after approximately 25 seconds of exposure. A 5 mm neoprene layer (k = 0.05 W nr’ K-1) maintains a surface temperature near 33 °C. Exposed skin declines to approximately 4-5 °C. A 200 pm silicone / microshell coating maintains approximately 16 °C at the surface. A 200 pm aerogel-like layer maintains approximately 25 °C. A 200 pm vacuum-like layer (k ~ 0.004 W nr' K-1) maintains approximately 30 °C. These results demonstrate the relative contributions of insulation thickness and thermal conductivity under high-convection conditions.

[0095] Example 5

[0096] FIG. 6 illustrates a plot of temperature increase over time of ex vivo skin samples coated with a variety of conductive / convective formulations. Top surfaces of skin samples were exposed to a hot radiative source (approximately 700 °C) and temperature measurements of an underside of the skin were made as a function of time following initiation of exposure. The samples include uncoated skin, Carrier 1 spray, Carrier 1 spray + glass microshells, Carrier 1 spray + glass microshells + a layer of silver nanowires on top, Carrier 1 spray + glass microshellsAtty. Dkt. No. 125141.04952.MGH2025-112-02+ aluminum powder on top, or Carrier 1 spray + glass microshells + a layer of silver coated microshells on top.

[0097] Example 6

[0098] FIG. 7 illustrates skin sections coated with a silicone gel + glass microshell thermal insulation formulation (right) and uncoated skin sections (left). Swine tissue is stained with NBTC showing viable tissue after contact with a 100 °C branding iron. In the uncoated tissue (left), there is ~lmm of nonviable dermis (white region at the top of the skin). For the coated tissue (right), the dermis remains viable.

[0099] FIG. 8 illustrates the conductive protection of ex vivo skin exposed to a branding iron at ~ 100 °C applied at a pressure of 0.7N for 5 seconds. The skin samples are either uncoated and unburned (panel A), uncoated and burned (panel B), coated with Carrier 1 spray (panel C), coated with Carrier 1 spray + glass microshells (panel D), coated with Carrier 1 spray + glass microshells + a layer of silver nanowires on top (panel E), coated with Carrier 1 spray + glass microshells + aluminum powder on top (panel F), or coated with Carrier 1 spray + glass microshells + a layer of silver coated microshells on top (panel G). NBTC staining shows that uncoated-burned and Carrier 1 -coated skin experienced burn damage, while samples with conductive / convective materials associated with Carrier 1 did not experience bum damage.

[0100] As used in this specification and the claims, the singular forms “a,” “an,” and “the” include plural forms unless the context clearly dictates otherwise.

[0101] As used herein, “about”, “approximately,” “substantially,” and “significantly” will be understood by persons of ordinary skill in the art and will vary to some extent on the context in which they are used. If there are uses of the term which are not clear to persons of ordinary skill in the art given the context in which it is used, “about” and “approximately” will mean up to plus or minus 10% of the particular term and “substantially” and “significantly” will mean more than plus or minus 10% of the particular term.

[0102] As used herein, the terms “include” and “including” have the same meaning as the terms “comprise” and “comprising.” The terms “comprise” and “comprising” should be interpreted as being “open” transitional terms that permit the inclusion of additional components further to those components recited in the claims. The terms “consist” and “consisting of’ should be interpreted as being “closed” transitional terms that do not permit the inclusion of additional components other than the components recited in the claims. The term “consisting essentiallyAtty. Dkt. No. 125141.04952.MGH2025-112-02of’ should be interpreted to be partially closed and allowing the inclusion only of additional components that do not fundamentally alter the nature of the claimed subject matter.

[0103] The phrase “such as” should be interpreted as “for example, including.” Moreover, the use of any and all exemplary language, including but not limited to “such as”, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed.

[0104] Furthermore, in those instances where a convention analogous to “at least one of A, B and C, etc.” is used, in general such a construction is intended in the sense of one having ordinary skill in the art would understand the convention (e.g., “a system having at least one of A, B and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and / or A, B, and C together.). It will be further understood by those within the art that virtually any disjunctive word and / or phrase presenting two or more alternative terms, whether in the description or figures, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A andB.”

[0105] All language such as “up to,” “at least,” “greater than,” “less than,” and the like, include the number recited and refer to ranges which can subsequently be broken down into ranges and subranges. A range includes each individual member. Thus, for example, a group having 1-3 members refers to groups having 1, 2, or 3 members. Similarly, a group having 6 members refers to groups having 1, 2, 3, 4, or 6 members, and so forth.

[0106] The modal verb “may” refers to the preferred use or selection of one or more options or choices among the several described embodiments or features contained within the same. Where no options or choices are disclosed regarding a particular embodiment or feature contained in the same, the modal verb “may” refers to an affirmative act regarding how to make or use an aspect of a described embodiment or feature contained in the same, or a definitive decision to use a specific skill regarding a described embodiment or feature contained in the same. In this latter context, the modal verb “may” has the same meaning and connotation as the auxiliary verb “can.”

Claims

Atty. Dkt. No. 125141.04952.MGH2025-112-02Claims1. A system for controlling a temperature of a subject, comprising:a spreadable formulation to coat a tissue surface, comprising:a fluid-based carrier; anda thermal control material contacting the fluid-based carrier, wherein the thermal control material is configured to control one or more of radiative heating, conductive heating, convective heating, radiative cooling, conductive cooling, or convective cooling.

2. The system of claim 1, wherein the fluid-based carrier is a cream, lotion, ointment, or film-forming agent.

3. The system of claim 1, wherein the fluid-based carrier further comprises components disposed therein in effective amounts to adjust one or more of an appearance, flowability, viscosity, adhesion, elasticity, thickness, odor, aqueous solubility, permeability, temperature resistance, or durability of the formulation.

4. The system of claim 3, wherein the components include one or more of surfactants, humectants, emollients, occlusives, antioxidants, preservatives, stabilizers, emulsifiers, thickeners, polymers, fragrances, or pigments.

5. The system of claim 1, wherein the fluid-based carrier includes one or more of polysiloxane or acrylate.

6. The system of claim 1, wherein the thermal control material configured to control radiative cooling or radiative heating includes one or more low-emissivity (low-E) materials.

7. The system of claim 6, wherein a plurality of parameters of the formulation adjusts infrared (IR) wavelength emission from the tissue surface relative to the tissue surface being uncoated.

8. The system of claim 7, wherein the plurality of parameters of the formulation adjusts emissions of wavelengths from 5-30 pm from the tissue surface relative to the tissue surface being uncoated.Atty. Dkt. No. 125141.04952.MGH2025-112-029. The system of claim 8, wherein the plurality of parameters includes one or more of intrinsic optical properties of the low-E materials, physical thickness of the formulation, concentration of the low-E materials, spatial distribution of the low-E materials within the formulation, or structural organization of the low-E materials within the formulation.

10. The system of claim 6, wherein the low-E materials include metals, metal-salts, or semiconductors.

11. The system of claim 10, wherein the low-E materials include solid particles, hollow particles, coated solid particles, coated hollow particles, flakes, one or more wires, one or more filaments, meshes, or continuous or perforated sheets.

12. The system of claim 10, wherein the low-E materials include one or more of gold, silver, copper, aluminum, Germanium, aluminum-doped zinc oxide, fluorine-doped tin oxide, antimony-doped tin oxide, or indium tin oxide.

13. The system of claim 6, wherein the low-E materials include alternating high refractive index and low refractive index dielectric layers configured to produce thin film interference.

14. The system of claim 13, wherein the high refractive index materials include germanium, silicone, or derivatives thereof.

15. The system of claim 6, wherein the low-E materials include diffusely reflective materials.

16. The system of claim 6, wherein the low-E material is distributed within the fluid-based carrier.

17. The system of claim 16, wherein the low-E material is homogeneously distributed within the fluid-based carrier.

18. The system of claim 16, wherein the low-E material is distributed along a concentration gradient within the fluid-based carrier.

19. The system of claim 6, wherein the low-E material contacts a surface of the fluid-based carrier opposite the tissue surface.

20. The system of claim 19, wherein the low-E material forms a regular or irregular pattern on the surface of the fluid-based carrier.Atty. Dkt. No. 125141.04952.MGH2025-112-0221. The system of claim 20, wherein the low-E material is electrically conductive at IR frequencies and is provided at a grid density necessary for the formulation to cross a percolation threshold.

22. The system of claim 21, wherein the grid forms a plurality of openings smaller than about one half of an IR emission wavelength.

23. The system of claim 6, wherein the low-E materials are provided at a quantity necessary to achieve an emissivity of less than 0.5.

24. The system of claim 6, wherein the low-E materials are provided at a quantity necessary to achieve an emissivity of less than 0.2.

25. The system of claim 1, wherein the thermal control material configured to control conductive heating, convective heating, conductive cooling, convective cooling, or combinations thereof includes thermal insulation materials.

26. The system of claim 25, wherein the thermal insulation material includes one or more airfilled glass microshells, hollow microspheres, aerogels, gas-filled low-density particles, or partially-evacuated low-density particles.

27. The system of claim 1, wherein the thermal control material is configured to self-separate within the carrier into one or more layers based on one or more of immiscibility, density differences between the thermal control material and fluid-based carrier, electrostatic charge, or surface charge.

28. The system of claim 1, where in the fluid-based carrier comprises one or more heat activated, chemically activated, or mechanically activated expanding materials.

29. The system of claim 28, wherein the mechanically activated expanding materials comprise expandable microstructures that form a cellular insulating structure upon expansion.

30. A method of controlling a temperature of a subject, comprising:applying the spreadable formulation of any one of claims 1-29 to a tissue surface of the subject.

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