Conductive and adhesive photonic crystal hydrogel based on non-dense colloid array as well as preparation method and application of conductive and adhesive photonic crystal hydrogel

Abstract

The invention discloses conductive and adhesive photonic crystal hydrogel based on a non-dense colloid array as well as a preparation method and application of the conductive and adhesive photonic crystal hydrogel. The method comprises the following steps: dissolving acrylamide, acrylic acid base and N, N '-methylene bisacrylamide in water to form a mixed solution, then adding a photoinitiator to obtain a hydrogel pre-gel solution, then adding a non-dense colloid array photonic crystal, MXene dispersion liquid and ion exchange resin, and carrying out ultrasonic dispersion to obtain the non-dense colloid array photonic crystal hydrogel. The obtained hydrogel pregel with the structural color is cured and polymerized under ultraviolet light, and the conductive and adhesive photonic crystal hydrogel based on the non-dense colloid array is prepared. The hydrogel not only has excellent toughness, conductivity, adhesiveness and light responsiveness, but also can be used as an electrode of a capacitor, sensitively and efficiently shows light and electricity bimodal response to tensile deformation and pressure deformation, and has application prospects in the fields of electronic skin, wearable equipment, human-computer interaction and the like.

Description

Technical Field

[0001] This invention belongs to the field of biomaterials and relates to a conductive, adhesive photonic crystal hydrogel based on a non-dense colloidal array, its preparation method, and its application. Background Technology

[0002] Structural color is a type of color widely found in the skin of many organisms in nature, a result of biological evolution. The structural color of biological skin is closely related to their lifestyles, such as shielding, communication, and other biological functions. Biomimetic structural color materials are widely used in many fields, including anti-counterfeiting encryption, biomimetic textile coloring, functional coatings, and cell / tissue engineering.

[0003] Human skin is a precise, accurate, and stable sensor capable of detecting motion, environmental conditions, and electrophysiology. With the development of bioelectronics and artificial intelligence, electronic skin that mimics the sensory functions of human skin has been developed and is attracting increasing attention. Current focus in electronic skin is on converting external stimuli (such as force and environmental changes) into easily readable and quantifiable signals, particularly electrical signals. Hydrogel-based electronic skin, possessing mechanical strength, adaptability, and biocompatibility, has made remarkable progress in emerging technology fields such as human-computer interaction, soft robotics, and personalized medicine systems. However, the development of multifunctional electronic skin hydrogels usually requires the filling of conductive particles and / or the modification of functional groups in the hydrogel network ([1]Ding Z,Li W,Wang W,et al.Highly Sensitive Iontronic Pressure Sensorwith Side-by-Side Package Based on Alveoli and Arch Structure[J].AdvancedScience,2024,11(24):2309407.;[2]Zhang Hui,Guo Jiahui,Wang Yu,et al.Stretchable and Conductive Composite Structural Color Hydrogel Films as Bionic Electronic Skins[J].Advanced Science,2021,8(20):2102156.). These functionalization processes may affect the formation of the periodic microstructure of the structural color hydrogel, leading to the destruction of the periodic photonic structure and the loss of structural color.

[0004] Unlike some natural biological skins that can autonomously adjust their functions and colors, current electronic skin systems place greater emphasis on sensing and execution capabilities. Reference 3 reports a piezocapacitive sensor with high sensitivity, but the sensor parameters can only be obtained through electrical detection, requiring relatively bulky instruments, which greatly limits the need for real-time monitoring ([3]Chen Minzhang, Wan Huixiong, Hu Yang, et al. Rationally designed cellulosehydrogel for an ultrasensitive pressure sensor[J].Materials Horizons,2023,10(10):4510-20.). Structural colors in nature, especially those that can autonomously change color, are used to transmit information to some extent, such as the skin of chameleons. Developing electronic skins with special functions similar to biological evolution, truly integrating with the natural environment, is the direction of next-generation devices. However, constructing multifunctional electronic skins with stable structural colors remains challenging. Summary of the Invention

[0005] To address the shortcomings of existing electronic skin, this invention provides a conductive, adhesive photonic crystal hydrogel based on a non-dense colloidal array, its preparation method, and its applications. This invention utilizes the synergistic effect of enhanced electrostatic repulsion and electronic conductivity to endow the hydrogel skin with enhanced photoelectric sensing stability and strong bio-interface adhesion without sacrificing the unique periodic structure of the photonic crystal.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] The preparation method of conductive, adhesive photonic crystal hydrogels based on non-dense colloidal arrays includes the following steps:

[0008] (1) A mixed solution is formed by dissolving acrylamide, adenine acrylate, thymine acrylate, and N,N'-methylenebisacrylamide in water, or by dissolving acrylamide, guanine acrylate, cytosine acrylate, and N,N'-methylenebisacrylamide in water, and then adding the photoinitiator 2-hydroxy-2-methyl-1-phenyl-1-propanone (HMPP) to obtain a hydrogel pregel solution. In the mixed solution, the mass concentration of acrylamide is 17.7wt% to 19.5wt%, the mass concentration of adenine acrylate, thymine acrylate, guanine acrylate, or cytosine acrylate is 0.1% to 0.5wt%, and the mass concentration of N,N'-methylenebisacrylamide is 0.3wt%.

[0009] (2) Add a non-dense colloidal array photonic crystal to the hydrogel pregel solution, and then add MXene dispersion and ion exchange resin. Mix evenly to obtain a hydrogel pregel with structural color.

[0010] (3) The pregel with structural color is placed under ultraviolet light to solidify and polymerize, thereby obtaining a conductive and adhesive photonic crystal hydrogel based on a non-dense colloidal array.

[0011] Furthermore, in step (1), the volume of HMPP is 1% to 5% of the volume of the mixed solution.

[0012] Further, in step (1), the mass concentration of acrylamide in the mixed solution is 18.7 wt%, the mass concentration of adenine acrylate, thymine acrylate, guanine acrylate or cytosine acrylate is 0.5 wt%, the mass concentration of N,N'-methylenebisacrylamide is 0.3 wt%, and the volume of HMPP is 3% of the volume of the mixed solution.

[0013] Furthermore, in step (2), the non-dense colloidal array photonic crystal is selected from silicon dioxide, titanium dioxide, or zinc sulfide nanoparticles, with a particle size of 60–200 nm. In a specific embodiment of the present invention, silicon dioxide is used as a representative example.

[0014] Further, in step (2), the concentration of the MXene dispersion is 10.6 mg / mL, the volume of the MXene dispersion is 2% to 4% of the volume of the hydrogel pregel solution, preferably 3%, and the amount of ion exchange resin added is 20 wt% to 40 wt% of the mass of the hydrogel pregel solution.

[0015] Furthermore, in step (2), the concentration of the non-dense colloidal array photonic crystal in the hydrogel pregel solution is 0.06–0.07 g / mL.

[0016] Furthermore, in step (2), the ion exchange resin is AG 501-X8.

[0017] The present invention provides a conductive, adhesive photonic crystal hydrogel based on a non-dense colloidal array prepared by the above preparation method.

[0018] Furthermore, the present invention provides the application of the above-mentioned conductive, adhesive photonic crystal hydrogel based on a non-dense colloidal array in the fabrication of electronic skin or flexible wearable devices.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] (1) This invention employs a strategy of immobilizing two-dimensional conductive materials and photonic crystals with acrylamide and acrylamide bases to prepare conductive and adhesive photonic crystal hydrogels based on non-dense colloidal arrays. The introduction of base pairs improves the adhesion and biocompatibility of the hydrogel, while the introduction of the two-dimensional conductive material MXene improves the stability and conductivity of the colloidal particle solution. This method is simple to operate and easy to industrialize.

[0021] (2) The conductive and adhesive photonic crystal hydrogel based on a non-dense colloidal array of the present invention has excellent toughness, conductivity, biocompatibility and photoresponsiveness. When subjected to external force, it will change optical and electrical signals, and has application prospects in the fields of electronic skin, wearable devices, and human-computer interaction. For example, it can be used in multimodal sensors. When the hydrogel is subjected to tensile strain, the color and resistance of the hydrogel will change. By detecting the color change and resistance change of the film, it can be used as a motion sensor to obtain the motion state; or as a hydrogel capacitor. Since it has a certain sensitivity to pressure, when the pressure changes, the color and capacitance of the hydrogel capacitor will change. Its structural color response and capacitance response can be used as the detection standard for visual pressure sensors.

[0022] (3) Compared with other sensor detection methods, the conductive and adhesive photonic crystal hydrogel based on non-dense colloidal array of the present invention can obtain qualitative detection results by observation, as well as quantitative detection results by detection instruments or systems, and such results have a certain degree of stability.

[0023] (4) The conductive and adhesive photonic crystal hydrogel based on the non-dense colloidal array of the present invention has excellent adhesion. It has strong interfacial adhesion to a variety of substrates (such as polytetrafluoroethylene, polyurethane, iron, acrylic, glass, wood, etc.) and has a wide range of applications. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the fabrication process of conductive, adhesive photonic crystal hydrogels based on non-dense colloidal arrays.

[0025] Figure 2 The image shows the adhesion results of conductive, adhesive photonic crystal hydrogels based on non-dense colloidal arrays to various substrates.

[0026] Figure 3 This image shows the optical and electrical sensing performance of a conductive, adhesive photonic crystal hydrogel based on a non-dense colloidal array. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to specific embodiments and accompanying drawings. These embodiments are merely descriptive and not limiting, and should not be construed as limiting the scope of protection of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention. Implementation conditions not specified in the embodiments are generally conditions found in conventional experiments.

[0028] In the following examples, the ion exchange resin used was AG 501-X8, purchased from Bio-Rad Laboratories, Inc., USA.

[0029] In the following embodiments, the non-dense colloidal array photonic crystal particles used are SiO2 nanoparticles, prepared according to existing methods, specifically as follows:

[0030] (1) Disperse SiO2 nanoparticles in ammonia water and add dropwise an ethanol solution of (3-mercaptopropyl)triethoxysilane;

[0031] (2) The SiO2 nanoparticles obtained in step (1) were treated by soaking in piranha solution and then separated by centrifugation;

[0032] (3) The particles were washed repeatedly with deionized water. After the particles were redispersed in water, a bright structural color was observed, and a non-dense colloidal array photonic crystal solution was obtained.

[0033] (4) Centrifuge the non-dense colloidal array photonic crystal solution, take the precipitate, and obtain the non-dense colloidal array photonic crystal.

[0034] Example 1

[0035] (1) Acrylamide (19.1 wt%), adenine acrylate (0.3 wt%), thymine acrylate (0.3 wt%) and N,N'-methylenebisacrylamide (0.3 wt%) were dissolved in water to form a mixed solution. Then, photoinitiator HMPP was added at a volume of 3% of the mixed solution to obtain a hydrogel pregel solution.

[0036] (2) The hydrogel pregel solution was added to the non-dense colloidal array photonic crystal to make the concentration of the non-dense colloidal array photonic crystal 0.07 g / mL. Then, different amounts of MXene dispersion (1% v / v, 2% v / v, 3% v / v, 4% v / v, 5% v / v or 6% v / v) and ion exchange resin (20 wt%) were added to the solution in sequence and mixed evenly to obtain a hydrogel pregel solution with structural color.

[0037] (3) The hydrogel pregel solution with structural color was irradiated under ultraviolet light and polymerized to obtain a conductive and adhesive photonic crystal hydrogel based on a non-dense colloidal array.

[0038] MXene exhibits excellent conductivity and provides a dark background for structural colors; appropriate amounts of MXene result in more uniform and brighter structural colors. However, due to its dark color, excessively high concentrations of MXene can negatively impact the gelation process of hydrogels under UV light (leading to prolonged gelation times or even failure to gel internally) and the brightness of the structural colors. Specifically, hydrogels with 1% v / v and 2% v / v MXene dispersions gel quickly, but due to their lower concentrations, their conductivity and structural color brightness are both lower. Hydrogels with 4% v / v MXene dispersions exhibit excellent conductivity and structural color brightness, but their gelation speed is slower. Hydrogels with 5% v / v and 6% v / v MXene dispersions exhibit excellent conductivity, but prolonged gelation times affect their mechanical properties, and the structural colors appear darker. Therefore, when preparing conductive, adhesive photonic crystal hydrogels based on non-dense colloidal arrays, the preferred addition amount of MXene dispersion is 3% v / v.

[0039] Example 2

[0040] (1) Acrylamide, adenine acrylate, thymidine acrylate (where the concentrations of acrylamide are 19.5wt%, 19.3wt%, 19.1wt%, 18.9wt%, 18.7wt%, 18.5wt%, 18.3wt%, 18.1wt%, 17.9wt%, or 17.7wt%, and the concentrations of adenine acrylate and thymidine acrylate are 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, or 1.0wt%) and N,N'-methylenebisacrylamide (0.3wt%) are dissolved in water to form a mixed solution. Then, photoinitiator HMPP is added at a volume of 3% of the mixed solution volume to obtain a hydrogel pregel solution.

[0041] (2) The hydrogel pregel solution was added to the non-dense colloidal array photonic crystal to make the concentration of the non-dense colloidal array photonic crystal 0.07 g / mL. Then, MXene dispersion (3% v / v) and ion exchange resin (20 wt%) with a concentration of 10.6 mg / mL were added to the solution in sequence and mixed evenly to obtain a hydrogel pregel solution with structural color.

[0042] (3) The pregel solution with structural color is irradiated under ultraviolet light and polymerized to obtain a conductive and adhesive photonic crystal hydrogel based on a non-dense colloidal array.

[0043] Adenine acrylate and thymine acrylate provide excellent adhesion properties for hydrogels, but excessively high concentrations of these compounds can affect the self-assembly speed of non-dense colloidal array photonic crystals and can also cause precipitation by complexing with MXene. Specifically, hydrogels with adenine acrylate to 0.5 wt% acrylate and thymine acrylate concentrations do not contain MXene precipitation, while hydrogels with concentrations of 0.6 wt% to 1.0 wt% contain MXene precipitation. Therefore, the preferred concentration of adenine acrylate and thymine acrylate in preparing conductive, adhesive photonic crystal hydrogels based on non-dense colloidal arrays is 0.5 wt%.

[0044] Example 3

[0045] 1. Preparation of conductive, adhesive photonic crystal hydrogels based on non-dense colloidal arrays:

[0046] (1) Acrylamide (18.7 wt%), adenine acrylate (0.5 wt%), thymine acrylate (0.5 wt%) and N,N'-methylenebisacrylamide (0.3 wt%) were dissolved in water to form a mixed solution, and then photoinitiator HMPP (3% v / v) was added to obtain a hydrogel pregel solution.

[0047] (2) The hydrogel pregel solution was added to the non-dense colloidal array photonic crystal to make the concentration of the non-dense colloidal array photonic crystal 0.07 g / mL. MXene dispersion (3% v / v) and ion exchange resin (20 wt%) with a concentration of 10.6 mg / mL were added to the solution and mixed evenly to obtain a hydrogel pregel solution with structural color.

[0048] (3) The pregel solution with structural color is irradiated under ultraviolet light and polymerized to obtain a conductive and adhesive photonic crystal hydrogel based on a non-dense colloidal array.

[0049] The conductive and adhesive photonic crystal hydrogel based on a non-dense colloidal array prepared in this invention exhibits excellent adhesion, demonstrating strong interfacial adhesion to various substrates, such as polytetrafluoroethylene, polyurethane, iron, acrylic, glass, and wood. Figure 2 As shown.

[0050] 2. Detect the resistance and structural color response of conductive, adhesive photonic crystal hydrogels based on non-dense colloidal arrays during deformation (tension, bending):

[0051] Clamp the hydrogel at both ends with tweezers and stretch it evenly towards both ends. During the stretching process, record its characteristic reflection peaks using a spectrometer and its real-time resistance using a Wheatstone bridge. Figure 3 As shown in Figure (A), the structurally colored hydrogel gradually changes from red to blue as the strain increases from 0% to 160%. The corresponding characteristic reflection peak of the hydrogel shifts from 656.57 nm to 523.00 nm, indicating that the strain state of the hydrogel can be quantitatively analyzed based on the shift in the reflection peak. The changes in structural color and characteristic reflection peak are due to the reduction in the interplanar spacing of the non-dense colloidal array photonic crystal during hydrogel stretching. Furthermore, during hydrogel stretching, the arrangement of MXene nanosheets in the hydrogel network changes from a "face-to-edge" state to a "face-to-face" state, resulting in a change in the resistance in response to strain. Figure 3 As shown in Figure (B), the relative resistance of the conductive, adhesive photonic crystal hydrogel based on a non-dense colloidal array changes by 293% as the strain increases from 0% to 160%. These results demonstrate that the conductive, adhesive photonic crystal hydrogel based on a non-dense colloidal array of this invention can be used as a dual-modal electronic sensor for limb micro-movements.

[0052] A conductive, adhesive photonic crystal hydrogel based on a non-dense colloidal array was adhered to a puppet's finger to simulate joint bending detection. Benefiting from strong hydrogen bonding interactions within the hydrogel network, the hydrogel achieved conformal adhesion to the gloved (nitrile) puppet finger. Characteristic reflection peaks were recorded using a spectrometer during bending, and its real-time resistance was recorded using a bridge circuit. As the finger joint bent to 0°, 30°, 60°, and 90°, the structural color of the conductive, adhesive photonic crystal hydrogel based on the non-dense colloidal array gradually changed from red to blue. Characteristic reflection spectra of the structural color hydrogel with five bending cycles were recorded to evaluate the sensor sensitivity and stability of the hydrogel. All experimental results show that the hydrogel exhibits corresponding characteristic reflection peaks at the same bending angle during different cycles. The deviation of the hydrogel's reflection peaks at the same bending angle during different cycles is small (within 4.35 nm), indicating that this type of structural color hydrogel sensor has strong optical sensing stability and sensitivity. The relative resistance changes of the conductive, adhesive photonic crystal hydrogel based on a non-dense colloidal array were recorded in real time during the bending process. As the bending angle of the finger joint increased (from 0° to 90°), the resistance of the structured color hydrogel showed an increasing trend. When the finger was cyclically bent at the same angle and in the same sequence, the real-time change in the hydrogel resistance remained relatively stable. These results indicate that the hydrogel prepared in this invention can serve as a high-performance dual-modal body surface electronic sensor.

[0053] 3. Detection of the capacitance and structural color response of a capacitor composed of a conductive, adhesive photonic crystal hydrogel based on a non-dense colloidal array and insulating tape under different pressures:

[0054] from Figure 3 As shown in Figure (C), the capacitance of the capacitor changes accordingly under different pressures to achieve pressure feedback. Due to the valuable ability of capacitive sensors to sense pressure and tension, they were adhered to a finger and studied as skin pressure sensors. Results showed that the capacitive sensor deforms as the finger bends, and the change in capacitance increases with the angle of finger bending. To further demonstrate the potential of this capacitive system in wearable sensors, the capacitive sensor was also adhered to the throat to monitor micro-movements on the throat skin during swallowing. The integrated capacitive sensor accurately recorded the participant's continuous swallowing movements. In addition to micro-movements on the skin, this capacitor can also handle complex motion monitoring. Figure 3 As shown in Figure (D), different letters are written on the capacitor surface, resulting in specific handwriting recognition signals and exhibiting high stability. These results demonstrate that this capacitance-based skin sensor can be used for writing pattern decoding. Notably, in addition to capacitance changes, the capacitor also exhibits color changes. Therefore, skin sensors composed of conductive, adhesive photonic crystal hydrogels based on non-dense colloidal arrays have significant application potential in fields such as electronic skin, wearable devices, and human-computer interaction.

Claims

1. A method for preparing conductive, adhesive photonic crystal hydrogels based on non-dense colloidal arrays, characterized in that, Includes the following steps: (1) A mixed solution is formed by dissolving acrylamide, adenine acrylate, thymine acrylate, and N,N'-methylenebisacrylamide in water, or by dissolving acrylamide, guanine acrylate, cytosine acrylate, and N,N'-methylenebisacrylamide in water, and then adding the photoinitiator 2-hydroxy-2-methyl-1-phenyl-1-propanone to obtain a hydrogel pregel solution. In the mixed solution, the mass concentration of acrylamide is 17.7 wt% ~ 19.5 wt%, the mass concentration of adenine acrylate, thymine acrylate, guanine acrylate, or cytosine acrylate is 0.1 ~ 0.5 wt%, and the mass concentration of N,N'-methylenebisacrylamide is 0.3 wt%. (2) Add a non-dense colloidal array photonic crystal to the hydrogel pregel solution, and then add MXene dispersion and ion exchange resin, mix evenly, and obtain a hydrogel pregel with structural color; (3) The pregel with structural color is placed under ultraviolet light to solidify and polymerize, thereby obtaining a conductive and adhesive photonic crystal hydrogel based on a non-dense colloidal array.

2. The preparation method according to claim 1, characterized in that, In step (1), the volume of 2-hydroxy-2-methyl-1-phenyl-1-propanone is 1% to 5% of the volume of the mixed solution.

3. The preparation method according to claim 1, characterized in that, In step (1), the mass concentration of acrylamide in the mixed solution is 18.7 wt%, the mass concentration of adenine acrylate, thymine acrylate, guanine acrylate or cytosine acrylate is 0.5 wt%, the mass concentration of N,N'-methylenebisacrylamide is 0.3 wt%, and the volume of HMPP is 3% of the volume of the mixed solution.

4. The preparation method according to claim 1, characterized in that, In step (2), the non-dense colloidal array photonic crystal is selected from silicon dioxide, titanium dioxide or zinc sulfide nanoparticles with a particle size of 60~200nm.

5. The preparation method according to claim 1, characterized in that, In step (2), the concentration of MXene dispersion is 10.6 mg / mL, the volume of MXene dispersion is 2% to 4% of the volume of hydrogel pregel solution, and the amount of ion exchange resin added is 20 wt% to 40 wt% of the mass of hydrogel pregel solution.

6. The preparation method according to claim 5, characterized in that, The volume of the MXene dispersion is 3% of the volume of the hydrogel pregel solution.

7. The preparation method according to claim 1, characterized in that, In step (2), the concentration of the non-dense colloidal array photonic crystal in the hydrogel pregel solution is 0.06~0.07 g / mL.

8. The preparation method according to claim 1, characterized in that, In step (2), the ion exchange resin is AG 501-X8.

9. The conductive, adhesive photonic crystal hydrogel based on a non-dense colloidal array prepared by any one of claims 1 to 8.

10. The application of the conductive, adhesive photonic crystal hydrogel based on a non-dense colloidal array according to claim 9 in the fabrication of electronic skin or flexible wearable devices.

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