3d printable hydrogels based on zein and methods of making and using the same

Abstract

The application discloses a 3D printable hydrogel based on gliadin, and discloses a preparation method and application thereof. The hydrogel is prepared from gliadin, quaternary ammonium salt chitosan, polyvinyl alcohol, genipin and molybdenum disulfide nanosheets; the gliadin is modified by using the quaternary ammonium salt chitosan to obtain modified gliadin; the modified gliadin and the polyvinyl alcohol are respectively prepared into solutions, and the two solutions are mixed, genipin is added for cross-linking reaction, and then molybdenum disulfide nanosheets are added to obtain 3D printable ink; the ink is printed into a grid with a surface microstructure, and after repeated freeze-thaw cycles, the 3D printable hydrogel is obtained. The hydrogel has excellent shear-thinning printability, mechanical strength, antibacterial performance and triboelectric output performance, and not only shows great potential in the field of green wearable self-powered sensors, but also has broad application prospects in the fields of human-computer interaction and sports health monitoring.

Description

Technical Field

[0001] This invention belongs to the field of biomass functional materials and flexible electronic devices, specifically relating to a 3D printable hydrogel based on gliadin. This invention also relates to the preparation method of the hydrogel and its application in constructing triboelectric nanogenerators and self-powered flexible wearable sensors. Background Technology

[0002] With the rapid development of flexible wearable electronic devices, the demand for sensing units that combine flexibility, biocompatibility, and self-powered capabilities is becoming increasingly urgent. Triboelectric nanogenerators (TENGs), as an emerging energy conversion device, rely heavily on the charge trapping ability and surface microstructure of the triboelectric layer material for their output performance. However, existing TENG triboelectric layer materials are mostly derived from petroleum-based polymers (such as PVDF), whose non-renewability and potential biocompatibility issues limit their application in the wearable field. While natural polymers offer environmental advantages, they often suffer from limitations such as poor water solubility, difficult molding, and low triboelectric output efficiency. Specifically: (1) Material limitations: Although gliadin is rich in polar groups and has the potential for triboelectric applications, its water insolubility seriously hinders its processing in water-based environmentally friendly ink systems; (2) Complex fabrication process: Traditional surface microstructure construction processes (such as photolithography and template method) used to improve TENG performance are complicated, costly and difficult to rapidly form complex three-dimensional structures on flexible substrates; (3) Single function: Existing bio-based friction layers often only focus on electrical output performance, lacking comprehensive consideration of mechanical strength, antibacterial protection and structural customizability, making it difficult to meet the complex needs of actual wearable scenarios.

[0003] Therefore, developing a multifunctional hydrogel material that combines excellent printability, high triboelectric output, good mechanical properties, and biofriendliness has become a key issue that urgently needs to be addressed in this field. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the present invention aims to provide a 3D printable hydrogel based on gliadin, which has excellent shear-thinning properties, mechanical properties and triboelectric output properties.

[0005] Another object of the present invention is to provide a method for preparing the above-mentioned hydrogel.

[0006] A third objective of this invention is to provide the application of the aforementioned hydrogel in triboelectric nanogenerators and self-powered flexible wearable sensors.

[0007] The technical solution adopted in this invention is a method for preparing 3D printable hydrogels based on gliadin, specifically as follows: Step 1: Weigh the raw materials according to the following weight proportions: 100 parts gliadin, 50-200 parts quaternary ammonium chitosan, 50-200 parts polyvinyl alcohol, 1 part genipin, and 0.2-1.0 parts molybdenum disulfide nanosheets; Step 2: Modify gliadin using quaternary ammonium salt chitosan to obtain modified gliadin. Step 3: Prepare solutions of modified gliadin and polyvinyl alcohol separately, mix the two solutions, add genipin for cross-linking reaction, and then add molybdenum disulfide nanosheets to obtain 3D printing ink. Step 4: Print the ink into a grid with surface microstructures, and after repeated freeze-thaw cycles, obtain a 3D printable hydrogel.

[0008] The invention is further characterized by: The diameter of the molybdenum disulfide nanosheets is 100~500nm.

[0009] Step 2 is as follows: Quaternary ammonium salt chitosan was dissolved in water to prepare a 2 wt% solution. Glycol protein was added to the solution, and the pH of the system was adjusted to 6.5. The mixture was stirred continuously at room temperature for 8-14 h to allow electrostatic adsorption to proceed fully. Subsequently, the mixture was pre-frozen at -50℃ to -45℃ for 8-14 h and then freeze-dried under vacuum for 36-48 h to obtain the quaternary ammonium salt chitosan modified glycol protein complex.

[0010] Step 3 specifically involves: Dissolve the modified gliadin obtained in step 2 in water; separately dissolve polyvinyl alcohol in water at 90-100℃ to prepare a 10wt% solution; after the polyvinyl alcohol solution cools, slowly add it to the modified gliadin solution and mix evenly; then add genipin at 55-60℃ in the dark for 3-3.5h for cross-linking reaction until the solution turns blue; finally add molybdenum disulfide nanosheets, stir and disperse evenly, and obtain 3D printing ink after vacuum degassing.

[0011] Step 4 is as follows: The 3D printable ink obtained in step 3 is loaded into the syringe of a direct-write 3D printer. The pneumatic pressure is set to 300~350kPa and the printing speed is 6-8mm / s. A grid with surface microstructure is printed using computer-aided design. After printing, the material is frozen at -20℃ for 10-12 hours and thawed at room temperature for 6-7 hours. The freeze-thaw cycle is repeated 3-4 times to obtain a 3D printable hydrogel.

[0012] In step 4, the surface microstructure is a multi-angled cross mesh structure, with printing angles alternating between 30°, 60° and 90°.

[0013] Another technical solution adopted in this invention is a 3D printable hydrogel based on gliadin, which is prepared by the above method.

[0014] The third technical solution adopted in this invention is the application of 3D printable hydrogels based on gliadin in triboelectric nanogenerators and self-powered flexible wearable sensors.

[0015] The beneficial effects of this invention are: (1) Excellent triboelectric output performance: Quaternary ammonium salt chitosan and gliadin were electrostatically self-assembled to construct a triboelectric active unit with a "core-shell" positive charge enrichment structure. During the triboelectric contact process, this structure can efficiently transfer electrons to the negative triboelectric layer, and its positive charge is far superior to that of the single-component system. Furthermore, MoS2 nanosheets were introduced as a charge trapping medium, relying on the two-dimensional interlayer deep trap energy level to store triboelectric charge and reduce charge return loss. The open circuit voltage of the prepared PHGM-TENG can reach 300V, which is more than 2 times higher than that of the unmodified natural protein material. The multi-angle grid structure TENG containing 0.2-1.0 parts of MoS2 has a short circuit current of 11.0μA and a transfer charge of 180nC, which is more than 50% higher than that of the flat sample.

[0016] (2) 3D printing has high printability and forming accuracy: The water solubility of gliadin was improved by modifying chitosan with quaternary ammonium salts, and the rheological properties were controlled by combining PVA and MoS2. The ink exhibits typical shear-thinning characteristics, and the zero-shear viscosity can reach 180 Pa. Based on the construction of a "chemically locked-physically regulated" dual network using genipin and MoS2, the printed material flows easily under shearing and quickly recovers its structural viscosity after extrusion. The extrusion is smooth and without collapse, and it can accurately prepare complex surface microstructures such as multi-angle cross meshes. The printing accuracy and molding stability are significantly better than those of single-component systems.

[0017] (3) Significantly enhanced mechanical properties: Genipin provides elastic recovery force for the hydrogel, and MoS2 acts as a rigid filler to achieve stress transfer. During the freeze-thaw cycle, the two work together to induce the orderly arrangement of polymer chains, so that the hydrogel can reach a stress of 90MPa under 500% strain, taking into account both high strength and high tensile properties.

[0018] (4) Good biocompatibility and antibacterial function: All raw materials used are derived from natural products and have excellent biofriendliness; Quaternary ammonium salt chitosan and MoS2 form a synergistic antibacterial effect, which can form obvious antibacterial zones against Staphylococcus aureus and Escherichia coli, meeting the hygiene and safety requirements for wearable devices to be used on the skin.

[0019] (5) Green and efficient preparation process: The one-pot physical-chemical cross-linking coupled direct writing 3D printing process is adopted, which does not require high temperature curing and toxic organic solvents. It has a fast molding speed and high material utilization rate, which is suitable for the customized green manufacturing production needs of flexible self-powered sensors. Attached Figure Description

[0020] Figure 1 This is a flowchart of the 3D printing process in the method of this invention; Figure 2 This is a schematic diagram showing the printing angles of 30°, 60°, and 90° in the method of the present invention; Figure 3 This is a TEM image of the quaternary ammonium salt modified gliadin prepared in Example 1 of the present invention; Figure 4 This is a comparison of XRD patterns before and after modification of gliadin with quaternary ammonium salt chitosan in Example 1 of the present invention. Figure 5 The images show infrared comparisons of gliadin before and after modification with quaternary ammonium salt in Examples 1-3 of this invention. Figure 6 The XPS full spectrum scan results and high-resolution spectra of C1s, N1s and Mo3d of PHGM prepared in Example 1 of this invention are shown. Figure 7 This is an EDS elemental distribution diagram of the PHGM hydrogel prepared in Example 1 of the present invention; Figure 8 Steady-state shear rheological curves for PVA solutions of different concentrations; Figure 9 The steady-state shear rheological curves of 10% PVA solution, HACC-Gli complex solution, PHG hydrogel and PHGM hydrogel in Example 1 of this invention are shown. Figure 10 The open-circuit voltage output curves of PHGM-TENG with different MoS2 nanosheet contents prepared in Comparative Example 1, Example 1 and Examples 4-7 are shown. Figure 11 The short-circuit current output curves of PHGM-TENG with different MoS2 nanosheet contents prepared in Comparative Example 1, Example 1 and Examples 4-7 are shown. Figure 12 The charge transfer output curves of PHGM-TENG with different MoS2 nanosheet contents prepared in Comparative Example 1, Example 1 and Examples 4-7 are shown. Figure 13 Open-circuit voltage output curves for PHGM-TENG with four different printing structures; Figure 14 Short-circuit current output curves for PHGM-TENG with four different printing structures; Figure 15 Output curves of transferred charge for PHGM-TENG with four different printed structures; Figure 16 The output voltage response curve of the PHGM-TENG sensor when it is attached to the human elbow; Figure 17 The output voltage response curve of the PHGM-TENG sensor when it is attached to the human knee. Figure 18 Output voltage response curve of the PHGM-TENG sensor when attached to the sole of the foot; Figure 19 The output voltage response curve of the PHGM-TENG sensor when it is attached to the palm of the hand; Figure 20 The results of the writing recognition test for the PHGM-TENG sensor are shown. Detailed Implementation

[0021] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0022] This invention relates to a 3D printable hydrogel based on gliadin, comprising the following components by weight: 100 portions of gliadin (Gli); Quaternary ammonium salt chitosan (HACC) 50-200 parts; Polyvinyl alcohol (PVA) 50-200 parts; One dose of ginseng; 0.2 to 1.0 parts of molybdenum disulfide nanosheets, preferably 0.4 parts.

[0023] Among them, the diameter of molybdenum disulfide nanosheets is 100~500nm.

[0024] This invention relates to a method for preparing a 3D printable hydrogel based on gliadin, which is implemented according to the following steps: Step 1, Preparation of Quaternary Ammonium Salt Modified Glycol Protein Complex: Quaternary ammonium chitosan was dissolved in a portion of distilled water to prepare a 2 wt% solution. Glycol protein was added to the solution, and the pH of the system was adjusted to 6.5 using 0.1 M sodium hydroxide solution. The mixture was stirred continuously at room temperature for 8-14 h to allow electrostatic adsorption to proceed fully. Subsequently, the mixture was pre-frozen at -50℃ to -45℃ for 8-14 h and then freeze-dried under vacuum for 36-48 h to obtain the quaternary ammonium chitosan-modified glycol protein complex HACC-Gli.

[0025] Step 2, Preparation of PHGM 3D Printing Ink: The HACC-Gli composite obtained in step 1 was dissolved in a portion of distilled water and stirred until completely dissolved. Polyvinyl alcohol was dissolved in the remaining distilled water in a water bath at 90-100℃ to prepare a 10wt% solution. After cooling, the solution was slowly added to the HACC-Gli solution and mixed evenly. Then, genipin was added at 55-60℃ in the dark to carry out a crosslinking reaction for 3-3.5 hours until the solution turned blue. Finally, molybdenum disulfide nanosheets were added, stirred and dispersed evenly, and vacuum degassing was performed to obtain PVA / HACC-Gli / MoS2 (PHGM) 3D printing ink.

[0026] Step 3, Construction of PHGM hydrogel: like Figure 1 As shown, the ink obtained in step 2 is loaded into the syringe of a direct-write 3D printer. The pneumatic pressure is set to 300~350kPa and the printing speed is 6-8mm / s. A grid with surface microstructure is printed using computer-aided design. After printing, the sample is frozen at -20℃ for 10-12 hours and thawed at room temperature for 6-7 hours. The freeze-thaw cycle is repeated 3-4 times to obtain PHGM hydrogel.

[0027] Among them, such as Figure 2 As shown, the surface microstructure is a multi-angled cross-grid structure, with printing angles alternating between 30°, 60° and 90°.

[0028] The aforementioned hydrogel can be used to construct triboelectric nanogenerators: the PHGM hydrogel after freeze-thaw cycles is cut and attached to the surface of a copper foil current collector as a positive friction layer, and an Ecoflex silicone rubber film is used as a negative friction layer to assemble a vertical contact-separation mode triboelectric nanogenerator (PHGM-TENG).

[0029] The core of this invention is to synergistically introduce two sets of key functional combinations into a natural protein-based hydrogel system, achieving fundamental innovation from the perspectives of material composites, structural construction, and functional regulation, as detailed below: Combination 1: An electrostatic self-assembly composite system of quaternary ammonium salt chitosan and gliadin.

[0030] In existing technologies, gliadin, due to its water insolubility, can typically only be used by dissolving it in organic solvents or by direct blending. Quaternary ammonium chitosan has also only been used alone as an antibacterial agent or cationic flocculant, and there is no research on the electrostatic self-assembly of these two to prepare triboelectric positive materials. This invention utilizes the high-density quaternary ammonium cations (-N) in the quaternary ammonium chitosan molecular chains under pH 6.5 conditions. +The electrostatic attraction between (CH3)3 and the weakly negatively charged carboxyl groups on the surface of gliadin creates a stable charge transfer interface, achieving molecular-level homogeneous composite. This combination not only fundamentally solves the water-soluble processing problem of gliadin, but more importantly, the high positive charge density of the quaternary ammonium groups forms a "positive charge enrichment shell" on the protein surface, making the positive charge of the complex significantly higher than that of any single component in the triboelectric sequence, laying the material foundation for the high output performance of TENG.

[0031] Combination 2: A synergistic system of genipin chemical cross-linking network and MoS2 nanosheet physical reinforcement network.

[0032] In existing technologies, genipin is only used as a fixative for biological tissues or a crosslinking agent for hydrogels, while MoS2 nanosheets are mostly used alone as lubricants, catalysts, or reinforcing fillers. There is currently no research on combining the two in natural protein-based 3D printing inks. This invention discovers that genipin covalently crosslinks with the amino groups on the protein and chitosan molecular chains, forming a permanent chemical network framework that runs through the entire hydrogel, endowing the material with permanent shape memory, structural integrity, and elastic recovery capabilities. Simultaneously, the uniformly dispersed MoS2 nanosheets form hydrogen bonds and van der Waals forces with the polymer matrix through the abundant sulfur atoms exposed on their surface, acting as secondary physical crosslinking points and forming a "soft-hard complementary" double crosslinking structure with the genipin chemical network. Furthermore, its two-dimensional layered interface possesses abundant deep trap energy levels, which can efficiently capture and store triboelectric charges.

[0033] The two components can also work synergistically: the genipin cross-linking network can constrain the uniform and stable dispersion of MoS2 nanosheets, preventing agglomeration and charge leakage; the uniformly dispersed MoS2, in turn, enhances the dielectric properties and charge storage capacity of the cross-linking network. The synergistic effect of the two components far exceeds that of the simple superposition of single components. At the same time, the reversible hydrogen bonds between MoS2 and the polymer chain enable the ink to desorb and flow under the shearing action of printing, and quickly reconstruct its viscosity after extrusion, achieving high zero-shear viscosity and shear-thinning characteristics, which is suitable for the molding requirements of direct-write 3D printing.

[0034] Example 1: This embodiment is based on a 3D printable hydrogel of gliadin, which includes the following components by weight: Based on genipin (set as 1 part), the remaining components are prepared in proportion.

[0035] 100 servings of gliadin; 100 parts of quaternary ammonium salt chitosan; 100 parts of polyvinyl alcohol; 0.4 parts of molybdenum disulfide nanosheets.

[0036] The preparation method includes the following steps: Step 1, Preparation of Quaternary Ammonium Salt Modified Glycol Protein: Dissolve 100 parts of quaternary ammonium salt chitosan in 4000 parts of distilled water and stir magnetically for 30 min until clear. Add 100 parts of glycol protein, adjust the pH to 6.5 using 0.1M NaOH, and stir at room temperature for 12 h. Pre-freeze the reaction solution at -50℃ and freeze-dry under vacuum for 48 h to obtain the HACC-Gli complex (1:1).

[0037] Step 2, PHGM ink preparation: Dissolve the HACC-Gli composite in 500 parts distilled water. Separately, dissolve 100 parts PVA in 900 parts distilled water (heat at 90°C for 2 hours), cool, and mix with the HACC-Gli solution. Then, add 1 part genipin under light-protected conditions in a 60°C water bath and stir for 3 hours until a blue color appears. Finally, add 0.4 parts MoS2 nanosheets, stir for 30 minutes, and degas under vacuum.

[0038] Step 3, 3D Printing and Cross-linking: Load the ink into the direct-write printer, set the air pressure to 320 kPa and the speed to 6 mm / s. Set the printing model to a multi-angle cross-grid (alternating printing angles of 30°, 60°, and 90°). After printing, perform three freeze-thaw cycles (freezing at -20°C for 12 hours / thawing at room temperature for 6 hours) to obtain the PHGM hydrogel.

[0039] Step 4, TENG device fabrication: Cut the hydrogel into 3cm×3cm pieces and attach them to the copper foil electrode. Use the Ecoflex film as the negative friction layer to assemble a vertical contact-separation TENG.

[0040] Example 2: The results are basically the same as in Example 1, except that the weight of quaternary ammonium chitosan is adjusted to 50 parts, and the mass ratio of gliadin to quaternary ammonium chitosan in the resulting HACC-Gli complex is 2:1.

[0041] Example 3: The results are basically the same as in Example 1, except that the weight of quaternary ammonium chitosan is adjusted to 200 parts, and the mass ratio of gliadin to quaternary ammonium chitosan in the resulting HACC-Gli complex is 1:2.

[0042] Example 4: The method is basically the same as in Example 1, except that the weight fraction of molybdenum disulfide nanosheets is adjusted to 0.1 parts.

[0043] Example 5: The method is basically the same as in Example 1, except that the weight of molybdenum disulfide nanosheets is adjusted to 0.2 parts.

[0044] Example 6: The method is basically the same as in Example 1, except that the weight of molybdenum disulfide nanosheets is adjusted to 0.3 parts.

[0045] Example 7: The method is basically the same as in Example 1, except that the weight of molybdenum disulfide nanosheets is adjusted to 0.5 parts.

[0046] Comparative Example 1: This comparative example is basically the same as Example 1, except that molybdenum disulfide nanosheets are not added.

[0047] Comparative Example 2: This comparative example is basically the same as Example 1, except that in step 3, 3D printing mesh construction is not performed. Instead, ink is directly poured into the mold for freeze-thaw cross-linking to form a blocky hydrogel with a smooth surface, which is named PHGM1.

[0048] Comparative Example 3: This comparative example is basically the same as Example 1, except that the printing angle in step 3 is 0° and 90°, and the resulting hydrogel is named PHGM2.

[0049] Comparative Example 4: This comparative example is basically the same as Example 1, except that the printing angle in step 3 is 45° and 135°, and the resulting hydrogel is named PHGM3.

[0050] The performance of various materials prepared in each embodiment and comparative example was tested, and the results are as follows: like Figure 3 The images show low-magnification and high-magnification TEM images of the modified gliadin HACC-Gli complex prepared in step 1 of Example 1. As can be seen from the images, the HACC-Gli complex exhibits a relatively uniform granular distribution, with particle sizes mainly concentrated in the 200-500 nm range, demonstrating good dispersibility and no obvious large-area aggregation. This indicates that the electrostatic interaction between HACC and Gli effectively promotes their uniform composite formation and avoids phase separation.

[0051] like Figure 4The image shows a comparison of XRD patterns before and after modification of gliadin using quaternary ammonium chitosan in Example 1. As can be seen from the image, the unmodified gliadin exhibits a broad, diffuse diffraction peak near 2θ=20°, a typical characteristic of the amorphous structure of protein peptide chains, indicating that Gli exists in an amorphous form and lacks long-range order in its molecular chain arrangement. The diffraction pattern of quaternary ammonium chitosan also shows a relatively broad, diffuse peak near 2θ=20°, but the peak intensity is significantly lower than that of Gli. This is attributed to the introduction of quaternary ammonium groups on the HACC molecular chain, which further disrupts the regular arrangement between chitosan molecular chains, reducing its crystallinity and exhibiting typical amorphous characteristics.

[0052] After modification with quaternary ammonium salt chitosan, the XRD pattern of the HACC-Gli complex also showed only a single broad and diffuse peak near 2θ=20°, and the peak intensity was further reduced compared to HACC. This phenomenon indicates that HACC and Gli achieved a homogeneous molecular-level composite through electrostatic interactions, and no macroscopic phase separation occurred between them. During the modification process, on the one hand, the rigid polysaccharide chains of HACC restricted its conformational changes and could not rearrange to form new crystalline regions; on the other hand, the positively charged groups on the HACC molecular chains and the negatively charged regions on the Gli molecular chains attracted each other, hindering the orderly arrangement of the molecular chains of each component, which further reduced the overall order of the composite system and decreased its crystallinity. The absence of characteristic sharp diffraction peaks attributable to any one raw material in the composite confirms the successful surface modification of Gli by HACC and the good compatibility between the two.

[0053] like Figure 5 The image shows a comparison of infrared spectra before and after modification of gliadin with quaternary ammonium salt in Examples 1-3. It can be seen from the image that in the Gli spectrum, at 3280 cm⁻¹... -1 The broad peak at 2925 cm⁻¹ is attributed to the OH / NH stretching vibration (amide A band). -1 and 2850cm -1 The vibration is a -CH2 stretching vibration, 1650 cm. -1 and 1530cm -1 The characteristic absorptions at 3400 cm⁻¹ of the amide I band (C=O) and amide II band (NH / CN) respectively confirmed the protein structure of Gli. In the HACC spectrum, the characteristic absorption at 3400 cm⁻¹... -1 The broad peak at 1480 cm⁻¹ is due to the OH / NH stretching vibration. -1 The characteristic absorption of the methyl group on the quaternary ammonium group was observed, confirming the successful introduction of the quaternary ammonium salt.

[0054] The HACC-Gli complex spectrum exhibits a regular change: as the proportion of HACC increases, the 3280 cm⁻¹ spectrum... -1 -3400cm -1The absorption peaks within the range gradually shift to higher wavenumbers and decrease in width, indicating that the introduction of HACC disrupted the original hydrogen bond network of Gli, forming new electrostatic / hydrogen bond interactions. The amide I band increases from 1650 cm⁻¹. -1 Gradually towards 1640cm -1 The offset, the amide II band strength weakens and is 1480 cm -1 The peak overlap reflects the contribution of HACC characteristics to the complex spectrum. No new sharp peaks or phase separation characteristics appeared in any of the complexes prepared in Examples 1-3, indicating that the two achieved homogeneous complexation at the molecular level.

[0055] Comparisons at different scales show that the 1:1 HACC-Gli sample, while retaining the main Gli structure, fully reflects the changes in the functional group environment after the introduction of HACC, and the interactions reach a good balance. FTIR results confirm that HACC and Gli successfully recombine through electrostatic / hydrogen bonding, providing a structural basis for subsequent ink composition optimization.

[0056] like Figure 6 The image shows the XPS full-spectrum scan results of PHGM prepared in Example 1, as well as the high-resolution spectra of C1s, N1s, and Mo3d. From the XPS full spectrum of PHGM, characteristic peaks of elements such as C, N, O, Mo, and S are observed. The C1s and O1s peaks are the most intense, originating from the main structure of the organic components (gliadin, quaternary ammonium chitosan, and PVA) in the hydrogel. The N1s peak originates from the protein amide group and quaternary ammonium group. The appearance of the Mo3d and S2p peaks confirms the successful introduction of MoS2 nanosheets. The high-resolution C1s spectrum is fitted with three characteristic peaks: 284.8 eV (C–C / C–H), 286.2 eV (C–O / C–N), and 287.8 eV (N–C=O / O–C=O), corresponding to alkyl side chains, oxygen-containing / nitrogen-containing groups, and amide / carboxyl carbons, respectively, confirming the coexistence and structural integrity of the organic components. The N1s spectrum showed two peaks at 399.5 eV and 400.0 eV. The former was attributed to neutral amino and amide nitrogen, while the latter was attributed to protonated amino and quaternary ammonium nitrogen. The presence of protonated nitrogen confirmed successful HACC recombination and maintenance of positive charge, which is beneficial for charge trapping during triboelectric charging. The two peaks at 229.0 eV and 232.1 eV in the Mo3d spectrum were attributed to Mo3d... 5 / 2 and Mo3d 3 / 2 Orbit, with Mo 4+ The characteristic peak positions matched, confirming that MoS2 was loaded into the hydrogel with a complete crystalline structure. No Mo was detected. 6+ The peak indicates that MoS2 did not undergo oxidative degradation during the preparation process.

[0057] XPS results show that the components of the PHGM hydrogel were successfully composited, and the organic components and MoS2 are well compatible through physical interactions. The material also maintains positive electrical properties, providing a structural basis for subsequent 3D printing and triboelectric property optimization.

[0058] like Figure 7 The image shows the EDS elemental distribution of the PHGM hydrogel prepared in Example 1, illustrating the distribution of five elements: C, N, O, Mo, and S. The EDS surface scan results show that C exhibits a uniform and dense distribution throughout the observation area, consistent with the high carbon content of the organic components (gliadin, quaternary ammonium chitosan, and polyvinyl alcohol) in the hydrogel matrix. N is also relatively uniformly distributed, but its signal intensity is slightly lower than that of C, attributed to the relatively low nitrogen content in proteins and quaternary ammonium chitosan. The uniform distribution of N confirms the good dispersion of nitrogen-containing components in the hydrogel system. The distribution of O highly overlaps with that of C and N, and is uniform, due to the widespread presence of oxygen-containing functional groups such as hydroxyl groups in polyvinyl alcohol and carbonyl and carboxyl groups in proteins. The uniform distribution of O further confirms the good compatibility between the components. The distribution maps of Mo and S show high consistency, with their enrichment areas completely overlapping and uniformly distributed throughout the observation field. This characteristic strongly confirms that MoS2 nanosheets were successfully loaded into the hydrogel network and exhibited good dispersion without significant large-area aggregation. The signal intensities of Mo and S elements were relatively lower than those of C, N, and O, which is consistent with the amount of MoS2 added to the system (0.4 parts). Notably, a slight enhancement of the signals of Mo and S elements was observed in the pore wall region, which corroborates the phenomenon of MoS2 nanosheets adhering to the pore wall surface observed in the SEM images.

[0059] Figure 8 Steady-state shear rheological curves of PVA solutions with different concentrations (3%, 5%, 8%, and 10%) are presented. It can be seen that all samples exhibit typical shear-thinning behavior, with viscosity gradually decreasing with increasing shear rate, and the viscosity decrease being more pronounced in higher concentration samples. When the shear rate reaches 150 s⁻¹... -1 At that time, the viscosity of the 3% and 5% PVA samples had decreased to a low level, while the 8% and 10% PVA samples maintained a certain viscosity, indicating that high-concentration PVA has more prominent shear-thinning sensitivity. This characteristic is suitable for the requirements of direct-write 3D printing: viscosity reduction under high shear facilitates ink extrusion, and rapid viscosity recovery after extrusion helps maintain the printed shape. Based on a comprehensive evaluation of viscosity level and shear-thinning performance, 10% PVA was ultimately selected as the base concentration for subsequent hydrogel preparation.

[0060] like Figure 9As shown, the steady-state shear rheological curves of the 10% PVA solution, HACC-Gli complex solution, PHG hydrogel (obtained after crosslinking reaction with genipin in step 2), and PHGM hydrogel prepared in each step of Example 1 are shown. It can be seen that the viscosity of the HACC-Gli complex solution is approximately 55 Pa·s at zero shear, attributed to the reversible physical crosslinking points formed by the electrostatic interaction between HACC and Gli; with increasing shear to 50 s... -1 The viscosity decreased to 0.3 Pa·s. The zero-shear viscosity of the 10% PVA solution was approximately 100 Pa·s, and its shear thinning was due to the disentanglement of molecular chain orientation, but it lacked effective cross-linking points, resulting in weak structural recovery. After introducing genipin chemical cross-linking into the PHG hydrogel, the zero-shear viscosity increased to approximately 150 Pa·s, and the double cross-linked network enhanced the structural strength. Further incorporating MoS2 nanosheets into the PHGM hydrogel resulted in a zero-shear viscosity of 180 Pa·s, attributed to the hydrogen bond adsorption and filler network effect of MoS2; the viscosity decreased to 0.2 Pa·s under high shear, comparable to PHG, indicating that MoS2 mainly enhances the low-shear structural strength without sacrificing flowability.

[0061] Figure 10-12 Output curves for open-circuit voltage, short-circuit current, and transferred charge of PHGM-TENG prepared with different MoS2 nanosheet contents (0 parts, 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, and 0.5 parts) in Comparative Example 1, Example 1, and Examples 4-7 are shown respectively. All tests were conducted under the same contact-separation frequency (1 Hz) and contact force (20 N). Figure 10 It can be seen that the open-circuit voltage first increases and then decreases with the increase of MoS2 content. The voltage is about 120V when no MoS2 is added (0 parts); it gradually increases to 140V, 160V and 180V when 0.1 parts to 0.3 parts are added; it reaches the maximum value of 200V when 0.4 parts are added, which is 66.7% higher than the sample without added MoS2; and it decreases to about 170V when 0.5 parts are added. Figure 11 The short-circuit current trend is consistent with that of the voltage. At 0 parts, the current is about 4.5 μA; at 0.1-0.3 parts, it increases to 5.0 μA, 5.5 μA, and 6.0 μA, respectively; at 0.4 parts, it reaches a maximum of 7.0 μA, which is 55.6% higher than the sample without the addition; at 0.5 parts, it decreases to about 6.2 μA. Figure 12 The trend of charge transfer was shown, which was highly consistent with the voltage and current. At 0 parts, the charge transfer was approximately 60 nC; from 0.1 to 0.3 parts, it increased to 70 nC, 80 nC, and 90 nC, respectively; at 0.4 parts, it reached a maximum of 110 nC, an increase of 83.3% compared to the unadded sample; at 0.5 parts, it decreased to approximately 95 nC. In summary, the MoS2 content has a regulatory effect on the charge trapping ability of the hydrogel, and 0.4 parts is the optimal addition amount.

[0062] Figure 13-15 The open-circuit voltage, short-circuit current, and transferred charge of four different printed PHGM-TENG structures are shown. PHGM1 is the unprinted block PHGM hydrogel (control group) from Comparative Example 2; PHGM2 is the orthogonal mesh structure formed by printing angles of 0° and 90° in Comparative Example 3; PHGM3 is the oblique mesh structure formed by printing angles of 45° and 135° in Comparative Example 4; and PHGM4 is the multi-angled complex mesh structure formed by printing angles of 30°, 60°, and 90° using the method of this invention. All tests were conducted under the same contact-separation frequency (1Hz) and contact force (20N). As can be seen from the figures, the output performance of the device significantly improves with increasing mesh structure complexity. The PHGM4 prepared by the method of this invention achieves an open-circuit voltage of 300V, a short-circuit current of 11.0uA, and a transferred charge of 180nC, exhibiting the best performance among the three samples. This performance improvement is mainly attributed to the increased effective contact area due to the surface microstructure.

[0063] The PHGM hydrogel prepared in Example 1 was cut into 1.5cm × 3cm rectangles, embedded in a porous sponge spacer layer, and sealed with insulating tape. These were then attached to the knee joint, palm, and sole of a shoe. An electrometer (Keithley 6517) was connected to collect signals in real time. The results are as follows: Figure 16-19 As shown, the PHGM-TENG sensor can effectively monitor the movement of different parts of the human body, including the flexion movements of the knee and elbow joints, the impact of the foot during running, and the swinging motion of a badminton racket. The sensor has good flexibility and durability, can adapt to repeated deformation under intense exercise conditions, and its output signal is stable and discernible.

[0064] Figure 20 The handwriting recognition test results of the PHGM-TENG sensor show that it exhibits excellent sensitivity and temporal resolution in handwriting recognition applications. It can clearly capture the stroke details when writing different characters (A, B, C) and accurately reproduce the timing characteristics of the "SOS" Morse code. The multi-angled cross-grid structure plays a crucial role in the sensing application: on the one hand, the grid structure enhances the device's sensitivity to minute pressures; on the other hand, the complex surface topology provides richer signal features for handwriting recognition.

Claims

1. A method for preparing a 3D printable hydrogel based on gliadin, characterized in that, Specifically: Step 1: Weigh the raw materials according to the following weight proportions: 100 parts gliadin, 50-200 parts quaternary ammonium chitosan, 50-200 parts polyvinyl alcohol, 1 part genipin, and 0.2-1.0 parts molybdenum disulfide nanosheets; Step 2: Modify gliadin using quaternary ammonium salt chitosan to obtain modified gliadin. Step 3: Prepare solutions of modified gliadin and polyvinyl alcohol separately, mix the two solutions, add genipin for cross-linking reaction, and then add molybdenum disulfide nanosheets to obtain 3D printing ink. Step 4: Print the ink into a grid with surface microstructures, and after repeated freeze-thaw cycles, obtain a 3D printable hydrogel.

2. The method for preparing a 3D printable hydrogel based on gliadin according to claim 1, characterized in that, The molybdenum disulfide nanosheets have a diameter of 100~500 nm.

3. The method for preparing a 3D printable hydrogel based on gliadin according to claim 1, characterized in that, Step 2 is as follows: Quaternary ammonium salt chitosan was dissolved in water to prepare a 2 wt% solution. Glycol protein was added to the solution, and the pH of the system was adjusted to 6.

5. The mixture was stirred continuously at room temperature for 8-14 h to allow electrostatic adsorption to proceed fully. Subsequently, the mixture was pre-frozen at -50℃ to -45℃ for 8-14 h and then freeze-dried under vacuum for 36-48 h to obtain the quaternary ammonium salt chitosan modified glycol protein complex.

4. The method for preparing a 3D printable hydrogel based on gliadin according to claim 1, characterized in that, Step 3 specifically involves: Dissolve the modified gliadin obtained in step 2 in water; separately dissolve polyvinyl alcohol in water at 90-100℃ to prepare a 10wt% solution; after the polyvinyl alcohol solution cools, slowly add it to the modified gliadin solution and mix evenly; then add genipin at 55-60℃ in the dark for 3-3.5h for cross-linking reaction until the solution turns blue; finally add molybdenum disulfide nanosheets, stir and disperse evenly, and obtain 3D printing ink after vacuum degassing.

5. The method for preparing a 3D printable hydrogel based on gliadin according to claim 1, characterized in that, Step 4 is as follows: The 3D printable ink obtained in step 3 is loaded into the syringe of a direct-write 3D printer. The pneumatic pressure is set to 300~350kPa and the printing speed is 6-8mm / s. A grid with surface microstructure is printed using computer-aided design. After printing, the material is frozen at -20℃ for 10-12 hours and thawed at room temperature for 6-7 hours. The freeze-thaw cycle is repeated 3-4 times to obtain a 3D printable hydrogel.

6. The method for preparing a 3D printable hydrogel based on gliadin according to claim 5, characterized in that, In step 4, the surface microstructure is a multi-angled cross-grid structure, with printing angles alternating between 30°, 60°, and 90°.

7. A 3D-printable hydrogel based on gliadin, characterized in that, It is prepared by the method described in any one of claims 1-6.

8. The application of the hydrogel as described in any one of claims 1-7 in triboelectric nanogenerators and self-powered flexible wearable sensors.

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