Confocal surface microlens array, microlens chip, preparation method and application

Abstract

The application provides a confocal surface microlens array and a method, comprising: a flexible positioning layer, comprising a plurality of microstructures, the microstructures being in the form of micro-pits, and the plurality of microstructures being arranged to form a micro-pit array; a plurality of microlenses, which are arranged correspondingly to the microstructures, any microlens being arranged in the microstructure, and the bottom edge of the microlens being closely attached to the bottom surface of the pit of the microstructure to form an initial coplanar array; and a cladding layer, which covers the surface of the initial coplanar array and embeds the part of the microlens exposed to air, the application achieving controllable array position, unified focal surface and stable structure through flexible microstructure guiding positioning, flip transfer coplanar retention and double-layer flexible or plastic material cladding strategies, and having good reproducibility and platform adaptability. In addition, the application also provides a microlens chip, a preparation method and an application.

Description

Technical Field

[0001] This application relates to the field of optical device technology, and in particular to a confocal microlens array, a microlens chip, a fabrication method, and its application. Background Technology

[0002] Microlenses (including but not limited to microspheres, perforated microspheres, micropillars, microellipsoids, microrings, etc.) are widely used in bioimaging, fluorescence detection, and single-molecule analysis due to their optical focusing, scattering modulation, and signal enhancement capabilities. With the increasing demand for standardization and high-throughput detection systems, researchers have gradually realized that constructing microlenses into structurally ordered and uniformly arranged arrays can effectively improve the comparability and reproducibility of detected images or signals. Especially when the microlens array is coplanar, all microlenses are located on a unified focal plane. Modulating the excitation beam on the confocal plane further helps obtain uniform and repeatable enhanced signals. Therefore, microlens arraying, especially the construction of coplanar arrays with unified focal planes, has become a key direction in the construction of optical enhancement platforms in recent years.

[0003] Existing methods for constructing microlens arrays mainly include liquid-phase self-assembly, interface-induced assembly, spin-coating deposition methods, template-assisted positioning, electric / magnetic / optical field-assisted assembly, and acoustic wave-driven assembly. Liquid-phase self-assembly is currently the most widely used method. It typically involves adding microlens suspension droplets to the substrate surface, utilizing the capillary force generated during solvent evaporation to drive the microlenses to migrate and aggregate in space, forming a tightly packed two-dimensional or three-dimensional structure. This method is simple to operate, suitable for constructing periodic structures such as colloidal crystals and photonic crystal films, and possesses a certain capacity for large-area film formation. In spin-coating deposition methods, researchers use the centrifugal force generated by high-speed rotation to push the microlenses towards the substrate edge, gradually distributing them radially and achieving a certain degree of uniform arrangement under controlled spin-coating rate and concentration. This method is suitable for rapid, large-area pattern coverage. In addition, interface assembly methods have also been applied in the construction of microlens arrays. These methods control the surface tension of the liquid-gas interface or liquid interface to make microlenses gather near the interface to form a single-layer array structure. Then, the microlens array is transferred to the target substrate through interface transfer and other methods. This method has certain advantages in the construction of thin-film arrays.

[0004] To further improve array positioning accuracy, existing technologies have also introduced template-assisted microstructure array guidance strategies. These methods involve pre-constructing micropores, micropillars, or pits on a substrate, such as through photolithography, nanoimprinting, or etching, to form structural units with specific dimensions and spacing. These units guide microlenses to precise positioning under gravity, capillary force, or imprinting. Commonly used template materials include SU-8 and polydimethylsiloxane (PDMS). Template-assisted methods typically combine drying deposition, imprinting curing, and spin-coating encapsulation to form immobilized arrays. These methods have all advanced the construction of microlens arrays to varying degrees, providing multiple pathways for array structure control, array region film formation, and microlens positioning, and are frequently used in research on optical device fabrication, enhanced imaging, and biosensing.

[0005] In existing self-assembly methods, the arrangement of microlenses on the substrate is affected by uncontrollable factors such as hydrodynamics and solution evaporation rate, resulting in random array positions, easy breakage, uneven density, and local accumulation, making it difficult to form a highly consistent array structure. In addition, due to the inherent fluctuations in microlens particle size, and the lack of tolerance adjustment mechanisms in traditional construction methods, the vertical height of microlenses is dispersed, and the focal plane position cannot be unified, significantly reducing the consistency of imaging signals and detection stability. Furthermore, existing technologies lack sufficient precision in controlling the array position, number, and spacing, and their construction results are limited by variables such as material concentration and spin coating parameters, making it difficult to achieve repeatable large-scale production. Summary of the Invention

[0006] In view of this, the present invention provides a confocal microlens array, a microlens chip, a fabrication method, and an application, which can improve the stability, standardization, and detection performance of the microlens array in the imaging system.

[0007] To solve the above problems, this application adopts the following technical solution: One objective of this application is to provide a confocal microlens array, comprising: The flexible positioning layer includes multiple microstructures, each microstructure being in the form of a micro-pit, and the multiple microstructures are arranged to form a micro-pit array; Multiple microlenses are disposed corresponding to the microstructure, with any one of the microlenses disposed within the microstructure and its bottom edge closely attached to the bottom surface of the pit of the microstructure to form an initial coplanar array. A coating layer covers the surface of the initial coplanar array and embeds the air-exposed portions of the microlenses.

[0008] In some embodiments, the flexible positioning layer is a curable polymer, and the surface of the curable polymer forms a regular array of micro-dimples. The micro-dimples include square arrays, honeycomb arrays, strip arrangements, or other regular patterns, and their arrangement density is designed from sparse arrays to dense and compact structures. The curable polymer system is selected from polydimethylsiloxane, polymethyl methacrylate, polyimide, epoxy resin, photosensitive resin, hydrogel, liquid crystal elastomer, or blends or copolymers thereof.

[0009] In some embodiments, the microlens is made of one or more combinations of barium titanate glass, titanium dioxide, polystyrene, melamine, polymethyl methacrylate, silicon, quartz, zirconium oxide, metal core-shell structure, and liquid crystal elastomer; the refractive index of the microlens is in the range of 1.1–3.5; and the diameter of the microlens can range from 50 nm to 1 mm.

[0010] In some embodiments, the upper and lower surfaces of the microlens lie in two parallel planes, and the equivalent principal plane or focal plane of all microlenses coincides with or is parallel to the planes.

[0011] In some embodiments, the coating layer includes PDMS, photosensitive resin, hydrogel, ionogel, liquid crystal elastomer, low refractive index fluoropolymer, porous film, quantum dot doped film, or a composite stack thereof.

[0012] The second objective of this application is to provide a method for fabricating a confocal microlens array, comprising the following steps: A flexible positioning layer is prepared, which includes multiple microstructures, each microstructure being in the form of a micro-pit, and the multiple microstructures are arranged to form a micro-pit array. Microlenses are respectively disposed within the microstructure, and the bottom edge of any microlens is closely attached to the bottom surface of the pit in the microstructure to form an initial coplanar array. A cladding layer is applied to the surface of the initial coplanar array, and the portion of the microlens exposed to air is embedded within the cladding layer.

[0013] In some embodiments, the flexible positioning layer is prepared by the following method: SU-8 photoresist microstructure templates are fabricated on templates using standard photolithography processes. The surface of the SU-8 photoresist microstructure templates is provided with a micropillar array. The PDMS prepolymer is coated onto the SU-8 photoresist microstructure template and the PDMS prepolymer fills the gaps between the micropillars. PDMS is cured by heating and then peeled off from the SU-8 photoresist microstructure template. A regular array of micro-concaves corresponding to the micropillar array is formed on the surface of the PDMS. At this time, the PDMS layer is the flexible positioning layer.

[0014] In some embodiments, the template includes silicon, quartz, glass, sapphire, metal, polymer, carbon nanotube array, two-dimensional material, or a stacked structure thereof.

[0015] In some embodiments, the micropillar array includes microstructural units, the shapes of which include cylinders, square pillars, elliptical cylinders, frustums, inverted cones, annular shapes, V-grooves, U-grooves, multi-step structures, or any combination thereof, and the size of the microstructural units is 50 nm–1 mm.

[0016] In some embodiments, the step of respectively arranging microlenses within the microstructure, with the bottom edge of any microlens closely adhering to the bottom surface of the pit in the microstructure to form an initial coplanar array, specifically includes the following steps: The microlenses are placed within the microstructure using methods such as roller coating, brush coating, spray coating, electrostatic spraying, microfluidic directional injection, centrifugal deposition, gravity sedimentation, vacuum adsorption, optical tweezers manipulation, magnetic manipulation, acoustic manipulation, or combinations thereof. The interaction of various forces causes the bottom edges of all the microlenses to conform to the bottom surface of the pits within the microstructure, forming an initial coplanar array structure.

[0017] In some embodiments, the step of covering the initial coplanar array surface with a cladding layer and embedding the air-exposed portion of the microlens within the cladding layer specifically includes the following steps: On the surface of the initial coplanar array, a coating material is spin-coated, and the spin-coating speed and viscosity are controlled so that the coating material can flow into the gaps between the microlenses and embed the air-exposed portions of the microlenses therein; the microlenses are then cured by heating or ultraviolet irradiation, and are bonded to the newly cured coating.

[0018] The third objective of this application is to provide a microlens chip, comprising: a confocal microlens array and a substrate as described in any one of claims 1 to 11, wherein: The coating layer is brought into close contact with the substrate, and the flexible positioning layer is peeled off, so that the microlens array is transferred onto the glass substrate, and the top of the microlens is fixed to the substrate surface by the coating layer.

[0019] In some embodiments, the substrate is selected from glass, quartz, sapphire, silicon, silicon carbide, silicon nitride, metal foil, polymer film, paper, fabric, biodegradable material, or a laminated structure thereof.

[0020] The fourth objective of this application is to provide a method for fabricating the aforementioned microlens chip, comprising the following steps: The entire structure with the coating and microlenses is flipped over so that the coating comes into contact with the substrate; The microlens array is transferred to the substrate as a whole using structural inversion and bonding techniques; The flexible positioning layer is peeled off, allowing the microlens array to be transferred onto the glass substrate, and the top of the microlens is fixed to the substrate surface by the covering layer.

[0021] In some embodiments, the structure inversion and bonding techniques include plasma bonding, ultraviolet ozone bonding, thermocompression bonding, adhesive bonding, van der Waals force bonding, metal eutectic bonding, anodic bonding, laser-assisted bonding, or combinations thereof.

[0022] In some embodiments, the method further includes the step of coating an optical film on the surface of the microlens array and controlling the film thickness so that it covers the top and sidewalls of the microlens but does not form an excessively thick planar layer on top of the microlens, thus forming a semi-enclosed state.

[0023] In some embodiments, the optical film includes PDMS, optical-grade UV adhesive, optical epoxy resin, or liquid crystal elastomer.

[0024] The fifth objective of this application is to provide an application of the aforementioned microlens chip in fluorescence imaging, scattering imaging, surface plasmon imaging, holographic imaging, photoacoustic imaging, Raman enhancement, digital pathology, AI training sample preparation, AR / VR display coupling, beam shaping, optical communication coupling, or a combination thereof.

[0025] The present application adopts the above technical solution, and its beneficial effects are as follows: The confocal microlens array provided in this application does not have randomly distributed microlenses. Instead, the positions of the microlenses are predefined by an array of micro-dimples on a flexible positioning layer. During the roll coating process, the micro-dimples act as predetermined seats, and their physical dimensions and spatial arrangement forcefully guide the microlenses to their designated positions. Since each dimple can only accommodate one microlens of a matching size, lens aggregation or misalignment is effectively avoided, ensuring a uniform and consistent lens distribution throughout the field of view and eliminating optical performance fluctuations caused by random positioning. Furthermore, this application utilizes gravity settling and the geometry of the dimples to achieve passive coplanarity calibration. After each microlens falls into a dimple, its bottom edge fits tightly against the bottom surface of the dimple. Because the bottom surfaces of all micro-dimples lie on the same continuous plane, the bottom edges of all microlenses are automatically aligned to the same initial focal plane, ensuring a natural consistency in focal plane height, optimizing optical imaging quality, and constructing a microlens array with consistent focal plane (optical axis direction) height, laying the foundation for high-quality imaging. The cladding layer covers and partially embeds the microlenses, flowing into the gaps between them, connecting the individual microlenses into an integrated composite structure. This mechanical interlocking greatly enhances the integrity of the array, and the stable structure makes subsequent operations such as flipping, plasma processing, and substrate bonding possible without compromising the array's integrity. This invention achieves controllable array position, unified focal plane, and structural stability through flexible microstructure-guided positioning, coplanar flipping and transfer maintenance, and a double-layer flexible or malleable material cladding strategy, exhibiting good reproducibility and platform adaptability.

[0026] The microlens chip provided in this application, with its current "partially embedded" structure fabricated from a confocal microlens array, is a key precursor for ultimately achieving semi-encapsulated or fully encapsulated optical interfaces. After removing the flexible positioning layer and spin-coating another layer of encapsulating material, the microlens is encased in a flexible thin film with a refractive index between that of the lens material and air. This encapsulating layer, acting as a refractive index gradient layer, significantly reduces Fresnel reflection between the microlens surface and air. According to optical principles, the intensity of reflected light is proportional to the square of the refractive index difference between the media on both sides of the interface. The encapsulating layer reduces this difference, thereby lowering the intensity of reflected light, allowing more incident light to be transmitted and used for imaging. This reduces stray light interference, directly improving image contrast and signal-to-noise ratio. Furthermore, for beam collection or illumination applications, higher transmittance translates to higher energy efficiency. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments of this application or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the structure of the confocal microlens array provided in Embodiment 1 of this application.

[0029] Figure 2 This is an SEM image of the flexible positioning layer provided in Embodiment 1 of this application.

[0030] Figure 3 This is a flowchart illustrating the fabrication process of the confocal microlens array provided in Embodiment 1 of this application.

[0031] Figure 4 This is a schematic diagram of the structure of the microlens chip provided in Embodiment 2 of the present invention.

[0032] Figure 5 This is a flowchart of the steps in the fabrication method of the microlens chip provided in Embodiment 3 of the present invention.

[0033] Figure 6 This is a schematic diagram of SEM imaging of the microlens chip provided in Embodiment 4 of the present invention.

[0034] Figure 7 This is a schematic diagram of bright-field microscopy imaging of a microlens chip provided in Embodiment 5 of the present invention.

[0035] Figure 8 This is a schematic diagram of fluorescence microscopy imaging of a microlens chip provided in Embodiment 5 of the present invention.

[0036] Figure 9 This is a schematic diagram of fluorescence microscopy imaging of a self-assembled microlens chip provided in Embodiment 5 of the present invention. Detailed Implementation

[0037] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application. In the description of this application, it should be understood that the terms "upper", "lower", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified. To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments.

[0038] Example 1 Please see Figure 1 This is a schematic diagram of the structure of a confocal microlens array provided in an embodiment of this application, including a flexible positioning layer, multiple microlenses, and a coating layer. The technical solution for its implementation is described in detail below.

[0039] The flexible positioning layer includes multiple microstructures, which are in the form of micro-pits, and the multiple microstructures are arranged to form a micro-pit array.

[0040] Please see Figure 2 The image shown is an SEM image of the flexible positioning layer. In this embodiment, the flexible positioning layer is a curable polymer. The surface of the curable polymer forms a regular array of micro-concave structures. The micro-concave array includes square arrays, honeycomb arrays, strip arrangements, or other regular patterns. The arrangement density is designed from sparse arrays to dense and compact structures. The curable polymer system is selected from polydimethylsiloxane, polymethyl methacrylate, polyimide, epoxy resin, photosensitive resin, hydrogel, liquid crystal elastomer, or their blends or copolymers.

[0041] It should be noted that the core function of this flexible positioning layer is to act as a high-precision "temporary mold" or "fixture," providing the physical basis for the precise positioning and coplanarity of the microlens. The surface of the flexible positioning layer is not flat, but rather has a large number of regularly arranged micro-dimples. These dimples are negative structures replicated from the SU-8 micropillar template prepared by photolithography using a molding process.

[0042] The arrangement of the micro-concave array can be flexibly designed according to the final optical requirements, and can take the following shapes: Square array structure: regular rectangular arrangement, simple to process, and easy to align with the pixels of digital image sensors.

[0043] Cellular array (hexagonal arrangement): This is the densest arrangement, which can achieve the highest fill factor, maximize the use of light transmission area, and reduce light energy loss. It is often used for high-performance imaging and beam homogenization.

[0044] Striped arrangement: suitable for specific applications such as line scan imaging, spectral analysis, or one-dimensional beam shaping.

[0045] Furthermore, the designability from sparse arrays to dense, compact structures means that this technology can cover a wide range of applications, from monitoring individual sample points to full-domain high-resolution imaging. High-density design enhances the integration and optical efficiency of the microlens array.

[0046] In this embodiment, the flexible positioning layer is composed of a curable polymer, and the specific system includes: Polydimethylsiloxane (PDMS): This is the preferred option due to its excellent flexibility, high transparency, extremely low curing shrinkage, good chemical stability, and inherent release properties.

[0047] Polymethyl methacrylate (PMMA), polyimide (PI), and epoxy resin: These materials offer higher rigidity and hardness, making them suitable for applications with extremely high requirements for dimensional stability, but they have poor flexibility.

[0048] Photosensitive resin: Suitable for direct molding using 3D printing technologies such as stereolithography (SLA) or digital light processing (DLP), and is suitable for rapid prototyping and the preparation of complex three-dimensional microstructures.

[0049] Hydrogels offer unique biocompatibility and adaptability to wet environments for biomedical applications such as cell culture and imaging integration.

[0050] Liquid crystal elastomers are a type of smart material whose micro-concave array structure can undergo controllable deformation under external stimuli (such as heat and light), laying the foundation for the development of reconfigurable and dynamically focusing microlens arrays.

[0051] The above materials can be modified by blending or copolymerization, and their mechanical modulus, surface energy, refractive index and other parameters can be precisely controlled to better adapt to the needs of different microlens materials and subsequent processes.

[0052] The flexible positioning layer provided in this embodiment enables "precise positioning" and "high-throughput self-assembly" of microlenses. The micro-dimples, acting as predefined seats, fundamentally ensure that each microlens reaches its designated position through their fixed spatial coordinates. During the roll coating process, a large number of microlenses can be automatically and in parallel filled into the dimples, representing a high-throughput, bottom-up self-assembly process. Compared to the traditional method of picking up microlenses one by one, efficiency is increased by orders of magnitude while avoiding mechanical damage. The bottom surfaces of all the micro-dimples together form an ideal reference plane. When a microlens sinks to the bottom of a dimple under gravity, its bottom edge fits tightly against this bottom surface. This physical process automatically aligns the optical reference planes of all microlenses to the same height, forming an "initial coplanar array." This coplanarity achieved through geometric structure is more fundamental, reliable, and efficient than active leveling or post-calibration. The flexible material properties make subsequent complex transfer processes possible; the flexibility allows the entire positioning layer to be bent and flipped, thus smoothly transferring the microlens array fixed on it to a rigid substrate (such as glass). The wide selection of polymer systems means that the most suitable positioning layer material can be selected according to different microlens materials (hydrophobic / hydrophilic) and different application environments (biological / industrial). By changing the master design, micro-concave arrays of different shapes (circular, square, annular), different arrangements, and different densities can be easily fabricated, thereby generating optical fields with different functions to meet various needs from standard imaging to advanced beam manipulation.

[0053] This flexible positioning layer solution achieves precise, coplanar positioning of microlenses through its regular micro-concave structure, and ensures the feasibility and multifunctionality of the process through its diverse flexible material system. Ultimately, it provides an indispensable foundation for the fabrication of high-performance, highly consistent, and customizable confocal microlens array chips.

[0054] Multiple microlenses are disposed corresponding to the microstructure, with any one of the microlenses disposed within the microstructure and its bottom edge closely attached to the bottom surface of the pit of the microstructure to form an initial coplanar array.

[0055] Each micro-dimple on the flexible positioning layer can be understood as a size-matched "seat" prepared for a single microlens. The opening diameter and depth of the dimple are calculated to ensure that, ideally, each dimple can only accommodate a microlens of the target particle size. Excess microlenses are dispersed on the surface of the positioning layer using roller coating or scraping techniques. Under the action of mechanical forces (rolling, vibration), the microlenses move randomly and fall into the size-matched dimples. The microlenses that fall into the dimples settle naturally under gravity. Their bottom edges (i.e., the lowest point in contact with the dimple) eventually achieve a tight fit with the optically flat bottom surface of the micro-dimple. Since the bottom surfaces of all dimples are on the same plane, the bottom edges of all microlenses are automatically aligned, forming an "initial coplanar array."

[0056] It is understandable that having all lenses at the same focal plane height avoids image blurring caused by height differences in traditional methods, ensuring high resolution across the entire field of view. A uniform focal plane means the highest concentration of light energy on the image plane, reducing crosstalk and significantly improving image contrast and signal-to-noise ratio. Precise coplanarity and parallelism reduce tilt aberrations caused by alignment errors, providing high-quality raw data for subsequent image processing.

[0057] Furthermore, this method utilizes gravity settling and geometric constraints to achieve self-assembly, a parallel process capable of handling millions of microlenses simultaneously. Compared to serial processes that require picking and placing each microlens individually, this significantly improves production efficiency, reduces manufacturing costs, and avoids mechanical damage.

[0058] In this embodiment, the microlens is made of one or more combinations of barium titanate glass, titanium dioxide, polystyrene, melamine, polymethyl methacrylate, silicon, quartz, zirconium oxide, metal core-shell structure, and liquid crystal elastomer. The refractive index of the microlens is between 1.1 and 3.5; the diameter of the microlens can range from 50 nm to 1 mm.

[0059] Specifically, high refractive index lenses are made of materials such as titanium dioxide (TiO2, n~2.4-2.7), zirconium oxide (ZrO2, n~2.1-2.2), and barium titanate glass (n~1.9-2.2) to achieve strong focusing capabilities and miniaturization.

[0060] Conventional refractive index lenses are made from polymers such as polystyrene (PS, n~1.59), melamine (n~1.55), and PMMA (n~1.49), which are low in cost and easy to synthesize into monodisperse microspheres.

[0061] Silicon (Si, n~3.5+) and quartz (SiO2, n~1.45): used in the infrared or ultraviolet bands.

[0062] Metal core-shell structures (such as Au@SiO2): Utilizing the plasmon effect of the metal core, surface-enhanced Raman scattering (SERS) detection and imaging are integrated.

[0063] Liquid crystal elastomers: provide the ability to respond to external stimuli (heat, light) to realize dynamic lenses with adjustable focus.

[0064] By selecting or combining materials from the above material library (such as preparing core-shell structured microspheres with different core and shell materials), a wide range of refractive indices, from below water (1.33) to far above ordinary glass, can be systematically covered to meet different needs from biological liquid environments to high-density integrated optical devices, enabling cross-scale diameter (50 nm – 1 mm) approaches.

[0065] In this embodiment, the upper and lower surfaces of the microlens are respectively located in two mutually parallel planes, and the equivalent principal plane or focal plane of all microlenses coincides with or is parallel to the planes.

[0066] It is understandable that the lower surface of all microlenses is defined as the first plane (reference plane) by the mechanism of "bottom edge fitting the bottom surface of the pit". Since the diameter of the microlenses is highly monodisperse, after they are "elevated" by the same reference plane, the envelope formed by the highest point of their top spherical surface naturally forms a second plane, which is parallel to the reference plane.

[0067] For a standard spherical microlens, its principal optical plane and focal plane are perpendicular to the lens's geometric axis of symmetry. When all the geometric axes of the lenses are perpendicular to the base plane (i.e., the upper and lower surfaces are parallel), their principal optical planes and focal planes must also be parallel to each other and parallel to or coincide with the reference plane. This, from an optical principle perspective, ensures that the convergence point (focal spot) of the outgoing rays lies on the same image plane.

[0068] It is understandable that this microlens assembly technology solves multiple complex problems such as "precise positioning," "coplanarity control," and "multifunctional integration" through a simple yet ingenious physical principle. It not only provides a method for fabricating high-performance microlens arrays but also represents a highly flexible and scalable multifunctional optical platform technology with direct, significant, and far-reaching technical effects.

[0069] The coating layer covers the surface of the initial coplanar array and embeds the air-exposed portion of the microlens.

[0070] In this embodiment, the coating layer includes PDMS, photosensitive resin, hydrogel, ionogel, liquid crystal elastomer, low refractive index fluoropolymer, porous film, quantum dot doped film, or a composite stack thereof.

[0071] It should be noted that the coating layer is a multi-step precision process. Its core lies in transforming the liquid precursor into a stable solid film that is tightly bonded to the microlens and substrate through spin coating and curing processes.

[0072] It can be understood that after the microlenses form an "initial coplanar array" in the flexible positioning layer through gravity settling, an uncured liquid prepolymer of the selected coating material (such as PDMS prepolymer, photosensitive resin, etc.) is spin-coated onto the array surface. By controlling the spin-coating speed, time, and liquid viscosity, the material can fully flow into and fill the gaps between the microlenses, and wrap the upper half of the spherical cap of each microlens, achieving "partial embedding." The curing at this stage aims to temporarily fix the microlenses into a whole, providing mechanical strength for subsequent flipping and transfer.

[0073] The selection of the coating material is key to achieving different technical effects. The materials listed in the solution can be divided into the following categories: PDMS: The preferred material. Due to its high light transmittance, excellent flexibility, low curing shrinkage, and good biocompatibility with glass / silicon substrates, it can perfectly achieve mechanical fixation and basic optical encapsulation.

[0074] Photosensitive resins (such as SU-8, acrylate UV adhesives): suitable for high-precision patterning (such as forming specific structures through mask exposure) or applications requiring higher hardness, with fast curing speed.

[0075] Hydrogels and ionogels: Introduce environmental responsiveness into devices. For example, the optical properties (such as focal length) of hydrogel-coated microlens arrays can change with variations in ambient humidity or pH, making them suitable for biosensing and wearable devices.

[0076] Liquid crystal elastomer: This is a smart material. Using it as a coating layer allows the entire microlens array to undergo controllable macroscopic deformation under external stimuli such as heat and light, thereby dynamically adjusting the focal length or arrangement of the microlenses and achieving adaptive optics.

[0077] Low-refractive-index fluoropolymers: Their refractive index (down to 1.3) is significantly lower than that of conventional polymers. Using them as the final coating layer can increase the refractive index difference between the microlens (n~1.5-1.9) and the coating layer. According to optical principles, this can increase the numerical aperture (NA) of the lens, thereby improving focusing ability and resolution.

[0078] Porous membranes (such as aerogels and porous SiO2 films): By using the air filled in the pores, a coating layer with an extremely low refractive index (n<1.2) can be prepared, which can further enhance the refractive index (NA) or be used as an anti-reflective layer.

[0079] Quantum dopant films: Quantum dots (CdSe / ZnS, perovskites, etc.) are incorporated into the coating matrix to endow the microlens array with wavelength conversion capabilities. For example, an ultraviolet light source can be converted into visible light of a specific color after passing through this chip, realizing a microstructured fluorescent light source with high color purity and high efficiency.

[0080] Thin films of different materials can be stacked to achieve multifunctional integration. For example, a layer of PDMS can be spin-coated first to achieve mechanical encapsulation, a layer of quantum dot-doped film can be spin-coated to achieve color conversion, and finally a layer of low-refractive-index fluoropolymer can be coated to protect and improve optical performance.

[0081] The coating layer effectively bonds individual microlenses into a single unit. This prevents the microlenses from shifting or detaching during subsequent demanding processes (such as plasma treatment, flipping, and tearing) and use, ensuring the long-term structural integrity of the array and forming the basis for high chip reliability. As a refractive index transition layer between the microlenses and air, the coating layer significantly reduces interface reflection losses caused by abrupt changes in refractive index, improving light transmittance and directly enhancing the signal-to-noise ratio and contrast of the image. By selecting low-refractive-index fluoropolymers or porous films, the effective focal length (NA) of the microlenses can be actively designed and increased, resulting in a smaller focused spot and higher optical resolution. The coating layer isolates sensitive microlens materials (such as easily oxidized metal core-shell structures and easily degradable perovskite quantum dots) from the external environment (oxygen, moisture), significantly improving the device's environmental stability and lifespan. Furthermore, coatings such as hydrogels and ionogels provide compatibility for applications in biological liquid environments.

[0082] The coating technology solution provided in this embodiment goes far beyond simple "encapsulation". It is a highly modular platform that, through diverse material selection and ingenious layered structure design, achieves basic mechanical fixation and optical anti-reflection while endowing the entire microlens array chip with outstanding characteristics of high performance, multifunctionality and intelligence, greatly expanding its application boundaries and technological ceiling.

[0083] The confocal microlens array provided in this application does not have randomly distributed microlenses. Instead, the positions of the microlenses are predefined by an array of micro-dimples on a flexible positioning layer. During the roll coating process, the micro-dimples act as predetermined seats, and their physical dimensions and spatial arrangement forcefully guide the microlenses to their designated positions. Since each dimple can only accommodate one microlens of a matching size, lens aggregation or misalignment is effectively avoided, ensuring a uniform and consistent lens distribution throughout the field of view and eliminating optical performance fluctuations caused by random positioning. Furthermore, this application utilizes gravity settling and the geometry of the dimples to achieve passive coplanarity calibration. After each microlens falls into a dimple, its bottom edge fits tightly against the bottom surface of the dimple. Because the bottom surfaces of all micro-dimples lie on the same continuous plane, the bottom edges of all microlenses are automatically aligned to the same initial focal plane, ensuring a natural consistency in focal plane height, optimizing optical imaging quality, and constructing a microlens array with consistent focal plane (optical axis direction) height, laying the foundation for high-quality imaging. The cladding layer covers and partially embeds the microlenses, flowing into the gaps between them, connecting the individual microlenses into an integrated composite structure. This mechanical interlocking greatly enhances the integrity of the array, and the stable structure makes subsequent operations such as flipping, plasma processing, and substrate bonding possible without compromising the array's integrity. This invention achieves controllable array position, unified focal plane, and structural stability through flexible microstructure-guided positioning, coplanar flipping and transfer maintenance, and a double-layer flexible or malleable material cladding strategy, exhibiting good reproducibility and platform adaptability.

[0084] Example 2 Please see Figure 3 This is a schematic flowchart of a method for fabricating a confocal microlens array provided in this embodiment, including the following steps: Step S10: Prepare a flexible positioning layer. The flexible positioning layer includes multiple microstructures, which are in the shape of micro-pits. The multiple microstructures are arranged to form a micro-pit array.

[0085] In this embodiment, the flexible positioning layer is prepared by the following method: Step S11: Prepare an SU-8 photoresist microstructure template on a template using a standard photolithography process. The surface of the SU-8 photoresist microstructure template is provided with a micropillar array.

[0086] In this embodiment, the template includes silicon, quartz, glass, sapphire, metal, polymer, carbon nanotube array, two-dimensional material or its stacked structure.

[0087] In this embodiment, the micropillar array includes microstructure units, the shape of which includes cylinder, square cylinder, elliptical cylinder, frustum, inverted cone, ring, V-groove, U-groove, multi-step or any combination thereof, and the size of the microstructure unit is 50 nm–1 mm.

[0088] Step S12: Coat the PDMS prepolymer onto the SU-8 photoresist microstructure template and fill the gaps between the micropillars with the PDMS prepolymer.

[0089] Step S13: Heat and cure PDMS and peel PDMS off from the SU-8 photoresist microstructure template. The PDMS surface forms a regular micro-concave array corresponding to the micropillar array. At this time, the PDMS layer is the flexible positioning layer.

[0090] A SU-8 photoresist microstructure template is fabricated on a silicon wafer using standard photolithography processes (such as ultraviolet lithography). The surface of this template is a designed array of micropillars, the size, shape, and spacing of which determine the final arrangement of the microlens array.

[0091] The process involves mixing a prepolymer of a flexible or malleable material (most typically polydimethylsiloxane (PDMS)) with a curing agent and pouring it onto an SU-8 template. The material is then spread evenly and fills the gaps between the micropillars using a doctor blade or a centrifuge (spin coating). The PDMS is then cured at a specific temperature (e.g., 60-80°C). After curing, the PDMS is carefully peeled off from the SU-8 template. At this point, a regular array of micro-pits corresponding to the SU-8 micropillar array has formed on the PDMS surface; this PDMS layer is called the "flexible positioning layer."

[0092] It should be noted that the core function of this flexible positioning layer is to act as a high-precision "temporary mold" or "fixture," providing the physical basis for the precise positioning and coplanarity of the microlens. The surface of the flexible positioning layer is not flat, but rather has a large number of regularly arranged micro-dimples. These dimples are negative structures replicated from the SU-8 micropillar template prepared by photolithography using a molding process.

[0093] Step S20: Microlenses are respectively arranged in the microstructure, and the bottom edge of any microlens is closely attached to the bottom surface of the pit of the microstructure to form an initial coplanar array.

[0094] Specifically, this embodiment employs a roller coating or scraper coating method. Excess microlens particles are dispersed on the surface of the PDMS positioning layer, and then gently rolled over the surface with a soft roller or scraper. Under the influence of mechanical force and vibration, the microlenses fall one by one into appropriately sized recesses. The diameter of the recess is slightly larger than the microlens particle size, but the depth is carefully designed to ensure that only one microlens can be accommodated in each recess. Under the influence of gravity, the microlenses falling into the recesses will naturally sink, and their bottom edges will closely adhere to the bottom surface of the recess. Since the bottom surfaces of all recesses are on the same plane (i.e., the lower surface of the PDMS layer), the bottom edges of all microlenses are naturally aligned, forming an "initial coplanar array." Excess microlenses that have not fallen into the recesses are removed by tilting or gently blowing air.

[0095] It is understandable that having all lenses at the same focal plane height avoids image blurring caused by height differences in traditional methods, ensuring high resolution across the entire field of view. A uniform focal plane means the highest concentration of light energy on the image plane, reducing crosstalk and significantly improving image contrast and signal-to-noise ratio. Precise coplanarity and parallelism reduce tilt aberrations caused by alignment errors, providing high-quality raw data for subsequent image processing.

[0096] Furthermore, this method utilizes gravity settling and geometric constraints to achieve self-assembly, a parallel process capable of handling millions of microlenses simultaneously. Compared to serial processes that require picking and placing each microlens individually, this significantly improves production efficiency, reduces manufacturing costs, and avoids mechanical damage.

[0097] Step S30: Cover the surface of the initial coplanar array with a cladding layer and embed the air-exposed portion of the microlens into the cladding layer.

[0098] Specifically, a layer of liquid-phase, flexible or malleable coating material (e.g., another layer of PDMS prepolymer or UV-curable adhesive) is spin-coated onto the surface of the array of microlenses. The spin-coating speed and viscosity are controlled to allow the coating material to flow into the gaps between the microlenses, partially embedding them without completely submerging them. Curing is then performed by heating or UV irradiation. At this point, the microlenses are "glued" into this newly cured coating, significantly enhancing their alignment stability.

[0099] As we can understand it, the cladding layer firmly bonds the individual microlenses into a single unit. This prevents the microlenses from shifting or detaching during subsequent demanding processes (such as plasma treatment, flipping, and tearing) and use, ensuring the long-term structural integrity of the array and forming the basis for high chip reliability. As a refractive index transition layer between the microlenses and air, the cladding layer significantly reduces interface reflection losses caused by abrupt changes in refractive index, improves light transmittance, and directly enhances the signal-to-noise ratio and contrast of the imaging.

[0100] The confocal microlens array provided in this application does not have randomly distributed microlenses. Instead, the positions of the microlenses are predefined by an array of micro-dimples on a flexible positioning layer. During the roll coating process, the micro-dimples act as predetermined seats, and their physical dimensions and spatial arrangement forcefully guide the microlenses to their designated positions. Since each dimple can only accommodate one microlens of a matching size, lens aggregation or misalignment is effectively avoided, ensuring a uniform and consistent lens distribution throughout the field of view and eliminating optical performance fluctuations caused by random positioning. Furthermore, this application utilizes gravity settling and the geometry of the dimples to achieve passive coplanarity calibration. After each microlens falls into a dimple, its bottom edge fits tightly against the bottom surface of the dimple. Because the bottom surfaces of all micro-dimples lie on the same continuous plane, the bottom edges of all microlenses are automatically aligned to the same initial focal plane, ensuring a natural consistency in focal plane height, optimizing optical imaging quality, and constructing a microlens array with consistent focal plane (optical axis direction) height, laying the foundation for high-quality imaging. The cladding layer covers and partially embeds the microlenses, flowing into the gaps between them, connecting the individual microlenses into an integrated composite structure. This mechanical interlocking greatly enhances the integrity of the array, and the stable structure makes subsequent operations such as flipping, plasma processing, and substrate bonding possible without compromising the array's integrity. This invention achieves controllable array position, unified focal plane, and structural stability through flexible microstructure-guided positioning, coplanar flipping and transfer maintenance, and a double-layer flexible or malleable material cladding strategy, exhibiting good reproducibility and platform adaptability.

[0101] Example 3 Please see Figure 4 This is a schematic diagram of a microlens chip structure provided in this embodiment, including the confocal microlens array and the substrate, wherein: The coating layer is brought into close contact with the substrate, and the flexible positioning layer is peeled off, so that the microlens array is transferred onto the glass substrate, and the top of the microlens is fixed to the substrate surface by the coating layer.

[0102] Specifically, a flat substrate is plasma-treated. This treatment cleans the substrate surface and generates numerous active groups such as hydroxyl (-OH) groups, increasing surface energy and making it highly hydrophilic and easily bonded. The entire structure, including the coating and microlenses, is flipped over, bringing the coating into contact with the treated substrate. Slight pressure is applied to ensure tight contact between the coating and the substrate. Due to their chemical properties (both are silicon-based) and the high surface energy after plasma treatment, irreversible bonding (usually covalent bonding) occurs. Once the bonding is stable, the initial flexible positioning layer is carefully peeled off. Because the interfacial bonding between the flexible positioning layer elastomer and the cured coating is weak, it can be completely peeled off. After peeling, the microlens array is successfully "released" from the pit and transferred to the glass substrate, with the top (original bottom edge) of the microlenses firmly fixed to the substrate surface by the coating.

[0103] In some embodiments, the substrate is selected from glass, quartz, sapphire, silicon, silicon carbide, silicon nitride, metal foil, polymer film, paper, fabric, biodegradable material, or a laminated structure thereof.

[0104] It's understandable that high-performance optical substrates such as glass and quartz are the standard choice, offering good light transmission and high surface flatness, making them suitable for most imaging and optical systems. Sapphire: Possesses extremely high hardness, wear resistance, and thermal stability, making it suitable for harsh environments or ultraviolet optics. Silicon, silicon carbide, and silicon nitride: These are key to optoelectronic co-integration; microlens arrays can be directly fabricated on the surface of CMOS or CCD image sensor chips, realizing chip-level optical systems, greatly reducing system size, and improving alignment accuracy and stability. Metal foils (such as polyimide copper-clad foil) and polymer films (such as PET and PI): These allow microlens chips to be bent and stretched, suitable for emerging fields such as flexible displays, skin-adhesive biosensors, and wearable health monitoring devices. Paper and fabrics: These enable low-cost, disposable, and reusable diagnostic devices (such as paper-based microfluidic imaging detection) and smart textiles (such as clothing with light-sensing capabilities). Biodegradable materials (such as polylactic acid PLA) give devices environmentally friendly and bioabsorbable properties, and can be used in temporary implantable medical devices. They degrade on their own after completing the monitoring task in the body, without the need for a second surgery to remove them.

[0105] By combining thin layers of different materials (such as covering a flexible PI film with a thin layer of glass), the advantages of both flexibility and ultra-flat surfaces can be obtained simultaneously.

[0106] Understandably, in the initial state, the coplanarity of the microlenses is guaranteed by the recessed bottom surface of the flexible positioning layer. After transfer, this coplanarity is frozen to the rigid substrate. The top of the microlens is fixed to the absolutely flat, rigid substrate surface by the cladding layer. Because all fixing points are in the same plane and the substrate itself does not deform, the focal plane consistency of the microlens array will be permanently maintained throughout the entire lifespan of the device, eliminating the inherent dimensional temperature drift and deformation risks of the flexible positioning layer, giving the chip excellent long-term dimensional and thermal stability. After transfer, the microlenses are firmly supported by the substrate, which provides a rigid base platform, and the cladding layer, which wraps around them from the top and sides, provides strong anchoring force and a strong chemical bond between the cladding layer and the substrate. This structure enables the chip to withstand mechanical stresses such as vibration and shock, meeting the stringent reliability requirements of commercial products. After transfer, light first passes through the high-optical-quality substrate, then directly into the microlens, and finally through the cladding layer into the air. This structure provides a protected, flat optical entrance window. Integration with image sensors (which typically come with their own protective glass) has become straightforward and standard. This creates ideal conditions for fabricating optical thin films such as anti-reflective coatings on the other side of the substrate, further optimizing overall optical performance.

[0107] Example 4 Please see Figure 5 The present application provides a flowchart of a method for fabricating a microlens chip, comprising the following steps: Step S40: Flip the entire structure with the coating layer and microlens so that the coating layer comes into contact with the substrate.

[0108] Specifically, at this point, the microlens has been filled into the recesses of the flexible positioning layer (such as PDMS) and has been "pre-fixed" by spin-coating a layer of uncured polymer (such as another layer of PDMS or UV adhesive). This pre-fixed coating has cured, encapsulating the upper part of the microlens to form a workable whole.

[0109] Specifically, the exposed surfaces of the pre-fixed coating and the glass substrate are treated with oxygen plasma to remove surface organic contaminants. For polymers such as PDMS, the plasma breaks the Si-CH3 bonds on their surfaces, generating a large number of silanol groups (-Si-OH). For glass, the number of silanol groups on its surface is also increased. This transforms both surfaces from hydrophobic to superhydrophilic.

[0110] The entire "flexible positioning layer-microlens-pre-fixed coating layer" structure is quickly flipped 180 degrees to align the activated coating layer surface and gently place it on the activated glass substrate. Apply uniform, gentle pressure (e.g., with a roller or flat-head tool) to remove interfacial air bubbles and ensure close contact between the two activated surfaces.

[0111] Step S50: The microlens array is transferred to the substrate as a whole using structural inversion and bonding techniques.

[0112] In some embodiments, the structure inversion and bonding techniques include plasma bonding, ultraviolet ozone bonding, thermocompression bonding, adhesive bonding, van der Waals force bonding, metal eutectic bonding, anodic bonding, laser-assisted bonding, or combinations thereof.

[0113] Under pressure, the silanol groups (-Si-OH) on the two activated surfaces undergo a condensation reaction, forming a strong Si-O-Si covalent bond. For PDMS-PDMS or PDMS-glass bonding, heating and holding at a certain temperature (e.g., 70-90°C) for 30-60 minutes is typically required to accelerate and complete this chemical reaction, achieving permanent bonding. For UV adhesives, bonding can be rapidly cured by exposure to ultraviolet light. At this point, the microlens array, through the coating layer, has formed a robust composite with the glass substrate. Structural inversion has been completed; the top of the microlens is fixed to the rigid substrate by the coating layer, while its bottom (the side originally in contact with the bottom of the pit) faces outwards.

[0114] Step S60: Peel off the flexible positioning layer so that the microlens array is transferred to the glass substrate, and the top of the microlens is fixed to the substrate surface by the covering layer.

[0115] After the bonding is stable, the initial flexible positioning layer (such as the PDMS layer) is slowly and evenly peeled off, starting from the edge, using your hand or tweezers. Since the flexible positioning layer may have been treated with a release agent before molding, or the interfacial bonding force between the flexible positioning layer (such as PDMS) and the pre-fixed coating layer above it is much weaker than the covalent bonding force between the coating layer and the glass substrate, "interfacial selective separation" can be achieved.

[0116] After peeling, the microlenses are completely "released" from the pits, their spherical surfaces fully exposed. The final structure is: glass substrate / robust cladding layer / microlens array. The top of the microlenses is anchored in the cladding layer, while the bottom forms a free, flat optical working surface.

[0117] In some embodiments, the method further includes the step of coating an optical film on the surface of the microlens array and controlling the film thickness so that it covers the top and sidewalls of the microlens but does not form an excessively thick planar layer on top of the microlens, thus forming a semi-enclosed state.

[0118] It is understandable that the formed thin film can wrap around the top and sidewalls of the microlens, forming a continuous protective and optically matching layer, but the highest point of the film is determined by the spherical profile of the microlens itself, rather than a thick planar layer covering all the lenses.

[0119] It is understandable that when light passes through media with different refractive indices, reflection (Fresnel reflection) occurs at the interface. If the microlens is directly exposed to air (n=1.0), due to its high refractive index (e.g., PS n=1.59, TiO2 n>2.0), the huge difference in refractive index leads to significant reflection loss (up to 4% or more per surface) and stray light. The refractive index of a semi-coated material (e.g., PDMS, n≈1.41) lies between that of air and the microlens. It acts as a transition layer, smoothing out the abrupt change in refractive index. According to optical principles, this greatly suppresses interface reflection, allowing more incident light to be transmitted into the microlens for effective focusing. This not only improves the system's light energy utilization but, more importantly, significantly reduces background noise caused by stray light, thereby directly and significantly improving the imaging contrast and signal-to-noise ratio.

[0120] Furthermore, this thin film isolates fragile microlens materials (especially easily oxidized metal core-shell structures or deliquescent perovskites) from the external environment (such as moisture, oxygen, dust, and mechanical scratches), improving the device's durability and lifespan. It further strengthens the bond between the microlens and the substrate, ensuring the long-term stability of the array. Unlike a fully sealed, thick planar layer, the semi-encapsulated state does not introduce additional, significant optical path aberrations. It does not produce aberrations or alter the original optical path design like a thick planar layer, perfectly balancing protection and optical performance.

[0121] Furthermore, specific optical thin-film materials can be selected to actively modulate performance. For example, using a low-refractive-index fluoropolymer (n<1.34) as a semi-coating layer can further increase the refractive index difference between it and the microlens core, thereby effectively increasing the numerical aperture (NA) of the microlens and obtaining a smaller focused spot and higher resolution. Wavelength conversion can be achieved by doping quantum dots in the thin film, or electro-optical focusing can be achieved by using liquid crystal elastomers, endowing the chip with new functions beyond imaging.

[0122] The microlens chip provided in this application, with its current "partially embedded" structure fabricated from a confocal microlens array, is a key precursor for ultimately achieving semi-encapsulated or fully encapsulated optical interfaces. After removing the flexible positioning layer and spin-coating another layer of encapsulating material, the microlens is encased in a flexible thin film with a refractive index between that of the lens material and air. This encapsulating layer, acting as a refractive index gradient layer, significantly reduces Fresnel reflection between the microlens surface and air. According to optical principles, the intensity of reflected light is proportional to the square of the refractive index difference between the media on both sides of the interface. The encapsulating layer reduces this difference, thereby lowering the intensity of reflected light, allowing more incident light to be transmitted and used for imaging. This reduces stray light interference, directly improving image contrast and signal-to-noise ratio. Furthermore, for beam collection or illumination applications, higher transmittance translates to higher energy efficiency.

[0123] Example 5 This application provides an application of the microlens chip described above in fluorescence imaging, scattering imaging, surface plasmon imaging, holographic imaging, photoacoustic imaging, Raman enhancement, digital pathology, AI training sample preparation, AR / VR display coupling, beam shaping, optical communication coupling, or a combination thereof.

[0124] Please see Figures 6 to 9 The microlens chip SEM imaging, microlens chip bright-field microscopy imaging, microlens chip fluorescence microscopy imaging, and self-assembled microlens chip fluorescence microscopy imaging provided in this embodiment are examples.

[0125] The confocal microlens array structure constructed in this invention is not only suitable for fluorescence-enhanced microscopy, but also for high-throughput image analysis platforms such as light scattering detection, digital nucleic acid analysis, TIRF (total internal reflection fluorescence) system integration, and image standardization training sample library construction, and has good scalability and system compatibility.

[0126] The above are merely preferred embodiments of this application, and only specifically describe the technical principles of this application. These descriptions are only for explaining the principles of this application and should not be construed as limiting the scope of protection of this application in any way. Based on this explanation, any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application, as well as other specific embodiments of this application that can be conceived by those skilled in the art without creative effort, should be included within the scope of protection of this application.

Claims

1. A confocal microlens array, characterized in that, include: The flexible positioning layer includes multiple microstructures, each microstructure being in the form of a micro-pit, and the multiple microstructures are arranged to form a micro-pit array; Multiple microlenses are disposed corresponding to the microstructure, with any one of the microlenses disposed within the microstructure and its bottom edge closely attached to the bottom surface of the pit of the microstructure to form an initial coplanar array. A coating layer covers the surface of the initial coplanar array and embeds the air-exposed portions of the microlenses.

2. The confocal microlens array as described in claim 1, characterized in that, The flexible positioning layer is a curable polymer, and the surface of the curable polymer forms a regular array of micro-concave structures. The micro-concave array includes square arrays, honeycomb arrays, strip arrangements, or other regular patterns, and its arrangement density is designed from sparse arrays to dense and compact structures. The curable polymer system is selected from polydimethylsiloxane, polymethyl methacrylate, polyimide, epoxy resin, photosensitive resin, hydrogel, liquid crystal elastomer, or blends or copolymers thereof.

3. The confocal microlens array as described in claim 1, characterized in that, The microlens is made of one or more of the following materials: barium titanate glass, titanium dioxide, polystyrene, melamine, polymethyl methacrylate, silicon, quartz, zirconium oxide, metal core-shell structure, and liquid crystal elastomer; the refractive index of the microlens is in the range of 1.1–3.5; and the diameter of the microlens can range from 50 nm to 1 mm.

4. The confocal microlens array as described in claim 1 or 3, characterized in that, The upper and lower surfaces of the microlenses are respectively located in two mutually parallel planes, and the equivalent principal planes or focal planes of all microlenses coincide with or are parallel to the planes.

5. The confocal microlens array as described in claim 1, characterized in that, The coating layer includes PDMS, photosensitive resin, hydrogel, ionogel, liquid crystal elastomer, low refractive index fluoropolymer, porous film, quantum dot doped film or composite stack thereof.

6. A method for fabricating a confocal microlens array, characterized in that, Includes the following steps: A flexible positioning layer is prepared, which includes multiple microstructures, each microstructure being in the form of a micro-pit, and the multiple microstructures are arranged to form a micro-pit array. Microlenses are respectively disposed within the microstructure, and the bottom edge of any microlens is closely attached to the bottom surface of the pit in the microstructure to form an initial coplanar array. A cladding layer is applied to the surface of the initial coplanar array, and the portion of the microlens exposed to air is embedded within the cladding layer.

7. The method for fabricating a confocal microlens array as described in claim 6, characterized in that, In the step of preparing the flexible positioning layer, it is specifically prepared by the following method: SU-8 photoresist microstructure templates are fabricated on templates using standard photolithography processes. The surface of the SU-8 photoresist microstructure templates is provided with a micropillar array. The PDMS prepolymer is coated onto the SU-8 photoresist microstructure template and the PDMS prepolymer fills the gaps between the micropillars. PDMS is cured by heating and then peeled off from the SU-8 photoresist microstructure template. A regular array of micro-concaves corresponding to the micropillar array is formed on the surface of the PDMS. At this time, the PDMS layer is the flexible positioning layer.

8. The method for fabricating a confocal microlens array as described in claim 7, characterized in that, The template includes silicon, quartz, glass, sapphire, metal, polymer, carbon nanotube array, two-dimensional material or its stacked structure.

9. The method for fabricating a confocal microlens array as described in claim 7, characterized in that, The micropillar array includes microstructure units, the shapes of which include cylinders, square pillars, elliptical cylinders, frustums, inverted cones, rings, V-grooves, U-grooves, multi-steps, or any combination thereof, and the size of the microstructure unit is 50 nm–1 mm.

10. The method for fabricating a confocal microlens array as described in claim 7, characterized in that, The step of correspondingly arranging microlenses within the microstructure, with the bottom edge of any one microlens closely adhering to the bottom surface of the pit in the microstructure to form an initial coplanar array, specifically includes the following steps: The microlenses are placed within the microstructure using methods such as roller coating, brush coating, spray coating, electrostatic spraying, microfluidic directional injection, centrifugal deposition, gravity sedimentation, vacuum adsorption, optical tweezers manipulation, magnetic manipulation, acoustic manipulation, or combinations thereof. The interaction of various forces causes the bottom edges of all the microlenses to conform to the bottom surface of the pits within the microstructure, forming an initial coplanar array structure.

11. The method for fabricating a confocal microlens array as described in claim 7, characterized in that, The step of covering the initial coplanar array surface with a coating layer and embedding the air-exposed portion of the microlens within the coating layer specifically includes the following steps: On the surface of the initial coplanar array, a coating material is spin-coated, and the spin-coating speed and viscosity are controlled so that the coating material can flow into the gaps between the microlenses and embed the air-exposed portions of the microlenses therein; The microlenses are bonded to the newly cured coating layer by curing through heating or ultraviolet irradiation.

12. A microlens chip, characterized in that, include: The confocal microlens array and substrate according to any one of claims 1 to 11, wherein: The coating layer is brought into close contact with the substrate, and the flexible positioning layer is peeled off, so that the microlens array is transferred onto the glass substrate, and the top of the microlens is fixed to the substrate surface by the coating layer.

13. The microlens chip as described in claim 12, characterized in that, The substrate is selected from glass, quartz, sapphire, silicon, silicon carbide, silicon nitride, metal foil, polymer film, paper, fabric, biodegradable material or its laminated structure.

14. A method for fabricating a microlens chip as described in claim 12, characterized in that, Includes the following steps: The entire structure with the coating and microlenses is flipped over so that the coating comes into contact with the substrate; The microlens array is transferred to the substrate as a whole using structural inversion and bonding techniques; The flexible positioning layer is peeled off, allowing the microlens array to be transferred onto the glass substrate, and the top of the microlens is fixed to the substrate surface by the covering layer.

15. The method for fabricating a microlens chip as described in claim 14, characterized in that, The structure inversion and bonding technologies include plasma bonding, ultraviolet ozone bonding, thermocompression bonding, adhesive bonding, van der Waals force bonding, metal eutectic bonding, anodic bonding, laser-assisted bonding, or combinations thereof.

16. The method for fabricating a microlens chip as described in claim 14, characterized in that, The method also includes the following steps: coating the surface of the microlens array with an optical thin film and controlling the film thickness so that it can cover the top and sidewalls of the microlens, but does not form an excessively thick planar layer above the microlens, thus forming a semi-enclosed state.

17. The method for fabricating a microlens chip as described in claim 16, characterized in that, The optical film includes PDMS, optical-grade UV adhesive, optical epoxy resin, or liquid crystal elastomer.

18. An application of a microlens chip as described in claims 12 to 16 in fluorescence imaging, scattering imaging, surface plasmon imaging, holographic imaging, photoacoustic imaging, Raman enhancement, digital pathology, AI training sample preparation, AR / VR display coupling, beam shaping, optical communication coupling, or a combination thereof.

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