Hydrogel-based oral flexible sensor for triboelectric-ion pressure and preparation method thereof

Abstract

The application discloses a triboelectric-ion pressure hydrogel-based oral flexible sensor and a preparation method. The application adopts a gelatin-based composite hydrogel as a flexible substrate, introduces MXene, ionic liquid and conductive polymer to construct a double-path signal transmission channel, designs a five-layer integrated stacking structure, and proposes a triboelectric non-contact motion sensing and ion supercapacitor pressure response cooperative sensing mechanism. By adjusting the ratio of functional fillers, the mandibular movement trajectory and occlusal force can be accurately monitored simultaneously. By optimizing the surface microstructure and gel components, the sensing signal output capability and long-term use stability can be ensured. The sensor can be used in temporomandibular joint disease diagnosis, denture occlusion detection, oral implant evaluation, tooth occlusion posture recognition and oral health intelligent monitoring.

Description

Technical Field

[0001] This invention relates to the fields of flexible hydrogel sensors and intelligent oral monitoring devices, and in particular to a hydrogel-based dual-function flexible oral sensor and its preparation method that simultaneously detects mandibular movement and occlusal force based on a triboelectric-ionic pressure dual-mode. Background Technology

[0002] With the continuous development of oral medicine, wearable medical electronics, and human-computer interaction technology, the demand for precise monitoring of intraoral occlusion, mandibular movement trajectory, and occlusal force is increasing. Flexible sensor devices are showing broad application prospects in scenarios such as oral diagnosis and treatment, denture fitting, and temporomandibular joint disease screening. Mandibular movement and occlusal force are core parameters for assessing the health of the stomatognathic system and formulating oral restoration and implant plans.

[0003] Traditional dental testing equipment has many shortcomings: electronic recorders, ultrasonic and optical testing devices are structurally separate, making it impossible to simultaneously acquire motion trajectory and occlusal force signals; the equipment is bulky, cumbersome to operate, and has poor patient comfort; traditional rigid pressure sensors have poor fit and are difficult to adapt to the complex curvature of teeth, resulting in limited detection accuracy; existing single-mode flexible sensors can only achieve single signal detection of motion or pressure, with low functional integration. Furthermore, conventional hydrogel sensing materials suffer from problems such as easy water loss, easy freezing at low temperatures, lack of self-healing ability, insufficient biocompatibility, and severe signal drift after long-term cyclic use, making it difficult to meet the requirements for long-term, stable, and high-precision monitoring in the high-humidity environment of the oral cavity.

[0004] Currently, the industry mainly improves the performance of flexible sensors by doping with functional fillers, optimizing material composition, and improving device structure. The composite sensing mechanism combining triboelectric sensing and ion pressure sensing has become a research direction due to its advantages of fast dynamic response and high pressure detection sensitivity. However, existing technologies still struggle to simultaneously achieve dual-signal synchronous acquisition, high detection accuracy, long-term stability, biosafety, and mechanical adaptability. Based on this situation, developing a hydrogel-based dual-function oral flexible sensor that integrates simultaneous detection of motion trajectory and occlusal force has significant clinical application value and engineering implications. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a hydrogel-based flexible oral sensor based on triboelectric-ion pressure and its preparation method.

[0006] In a first aspect, the present invention provides a method for preparing a hydrogel-based flexible oral sensor based on triboelectric-ionic pressure, comprising the following steps: S1. Preparation of multilayer functional hydrogel membranes a. Preparation of spacer layer hydrogel (SLH) raw materials: Sodium chloride, glycerol, and deionized water were mixed and magnetically stirred at 1000 rpm for 30 min at room temperature. Gelatin was then added and allowed to swell for 2 h. Subsequently, the mixture was placed in a 75 ℃ water bath and stirred continuously at 3000 rpm for 1 h to obtain a homogeneous gel precursor solution. The mass ratio of sodium chloride, glycerol, gelatin, and deionized water was 0.46:3:2:4. The precursor solution was injected into a square frame mold and frozen to obtain a rectangular ring-shaped spacer layer hydrogel.

[0007] b. Preparation of Triboelectric Layer Hydrogel (TLH) Raw Materials: The basic formulation system of the spacer layer hydrogel is used, but deionized water is replaced with 8% (w / w) Ti3C2T. x (MXene) aqueous dispersion, with the proportions of other materials, stirring temperature and stirring speed remaining unchanged; after thorough stirring, it is placed in an ice-water bath for ultrasonic treatment to obtain the triboelectric layer gel precursor solution.

[0008] c. Preparation of UELH hydrogel raw materials for the upper electrode layer: Using the basic formulation system of spacer layer hydrogel, deionized water was replaced with an equal volume of PEDOT:PSS solution and BMIM-BF6 ionic liquid mixture. The mixture was magnetically stirred at 40 ℃ until the system was completely homogeneous to obtain the electrode layer gel precursor solution; wherein, the volume ratio of gel matrix, PEDOT:PSS and ionic liquid was 2:1:1.

[0009] d. Preparation of raw materials for electrolyte layer hydrogel (EYLH): Using the basic formulation system of spacer layer hydrogel, deionized water was replaced with an equal volume of deionized water and ionic liquid BMIM-BF6 mixture, with the ionic liquid volume accounting for 20% of the total solvent volume; the mixture was thoroughly mixed by magnetic stirring at 50 ℃ to obtain the electrolyte layer gel precursor solution.

[0010] e. Preparation of raw materials for the lower electrode layer hydrogel LELH: The raw material ratio, stirring process and process parameters are consistent with those in step c, and the lower electrode layer gel precursor solution is obtained.

[0011] f. Functional hydrogel molding and microstructure construction: The above-mentioned TLH, UELH, EYLH and LELH precursor solutions were injected into flat molds with dimensions of 2cm×3cm×0.01cm and leveled. A network microstructure was constructed on the surface of the gel using a screen printing process. After low-temperature freeze-curing, the gels were demolded to obtain the corresponding functional hydrogel films. Combined with the annular spacer layer hydrogel obtained in step a, the preparation of all functional hydrogel units was completed.

[0012] S2. Assembly of a dual-function oral flexible sensor The multilayer functional hydrogel structure prepared in step S1 is sandwiched between two silver electrodes of the same specification, and signal wires are led outwards. The entire structure is sealed and encapsulated with a biocompatible flexible waterproof membrane and cured at a constant temperature to obtain a triboelectric-ion pressure dual-function oral flexible sensor.

[0013] Furthermore, in steps S1b-S1d, the ionic liquid used is 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-BF6) with a purity ≥98%; the two-dimensional conductive filler is Ti3C2T. x (MXene), purity ≥99%.

[0014] Furthermore, in step S1a, sodium chloride and glycerol are used as functional additives. The mass ratio of sodium chloride to gelatin is 0.23:1, and the mass ratio of glycerol to gelatin is 1.5:1. Glycerol can improve the water retention and antifreeze properties of the hydrogel, while sodium chloride is used to replenish free ions in the system.

[0015] Furthermore, in step S1b, the ultrasonic treatment conditions are: 500 W power ultrasonic treatment for 12 min, with the working mode being ultrasonic for 1.5 s and pause for 2 s; the entire process is carried out in an ice-water bath environment to prevent MXene sheet aggregation and premature solidification of the gel precursor solution.

[0016] Furthermore, in step S1f, the freeze-curing temperature is set to -20 ℃ and the curing time is 60 min; the screen printing uses a 100-250 mesh screen to construct a uniform network microstructure on the hydrogel surface.

[0017] Furthermore, in step S2, the thickness of the silver electrode is 0.01 mm, and the thickness of the biocompatible flexible waterproof membrane is 0.04 mm.

[0018] Furthermore, in step S2, the curing conditions after encapsulation are: constant temperature holding at 45 ℃~50 ℃ for 8 min~12 min.

[0019] Secondly, the present invention provides a hydrogel-based flexible oral sensor for triboelectric-ion pressure prepared by the above-described preparation method.

[0020] This application has the following beneficial effects.

[0021] This invention uses a gelatin-based composite hydrogel as a flexible matrix, and incorporates MXene, ionic liquid, and PEDOT:PSS to construct a dual-channel signal transmission system. Utilizing a synergistic sensing mechanism of triboelectric non-contact sensing and ionic supercapacitor pressure response, it can simultaneously perform high-precision detection of mandibular movement trajectory and occlusal force. The signal attenuation of the triboelectric unit is less than 5% after 10,000 consecutive cycles, and the ionic pressure unit achieves a sensitivity of 4.97 kPa in the 10–40 kPa range. -1 With a response time of 1 second and a recovery time of 1.6 seconds, the overall accuracy of bite posture recognition reaches 99.25%. This invention's sensor possesses excellent signal linearity, cyclic stability, interfacial adhesion, and self-healing properties. Furthermore, the hydrogel material exhibits a cell survival rate exceeding 85%, with no skin or oral mucosal irritation and good biocompatibility. This product can be widely applied in temporomandibular joint disease diagnosis, denture fit testing, dental implant program evaluation, tooth bite posture recognition, and long-term intelligent monitoring of oral health. It can also be integrated into various wearable oral devices, providing a novel device solution and technical support for intelligent detection and treatment in oral medicine. Attached Figure Description

[0022] Figure 1 Overall design of a flexible sensing system for measuring mandibular movement trajectory and occlusal force.

[0023] Figure 2 Fabrication, characterization, and performance analysis of a dual-function flexible sensor: (A) Schematic diagram of the fabrication process of SLH; (B) Macroscopic morphology of TLH; (C) Scanning electron microscopy of the microstructure of TLH; (D) Energy dispersive spectroscopy of elemental distribution in ELH; (E) Macroscopic morphology of ELH; (F) Macroscopic morphology of EYLH; (G) Scanning electron microscopy of cross-section of EYLH gel; Figure 3 Sensing mechanism and performance characterization of triboelectric unit: (A) Working mechanism of triboelectric unit; (B) COMSOL simulation results of triboelectric unit; (C) Schematic diagram of linear motor test platform; (D) Output current curve; (E) Output charge curve; (F) Output voltage curve; (G) Current and voltage characteristics under different resistances; (H) Power characteristics under different resistances; (I) Relationship between triboelectric peak voltage and contact distance; (J) Output voltage at different frequencies; (K) Voltage comparison between different friction materials; (L) Voltage stability test results for more than 10,000 s.

[0024] Figure 4The sensing mechanism and performance characterization of the ion-supercapacitor unit are as follows: (A) Sensor working mechanism; (B) Stress distribution simulation results; (C) Performance comparison with and without spacer layer; (D) Effect of different ionic liquid concentrations on performance; (E) Performance comparison of different surface microstructures; (F) Sensitivity curves of two linear regions; (G) Response characteristics under slight pressure; (H) Response time and recovery time test; (I) Dynamic response capacitance change rate of the sensor under different pressures; (J) Dynamic response characteristics of the sensor at different frequencies; (K) Stability test of capacitance change rate after more than 1000 cycles.

[0025] Figure 5 Flexible sensing system for oral occlusion and its performance characterization: (A) Wearing and actual appearance of intraoral sensors; (B) System architecture for occlusion signal acquisition and data processing; (C) Triboelectric and capacitive signals of tooth opening, occlusion, and other actions; (D) Triboelectric signals at three different locations on the lateral surface of the teeth; (E) Triboelectric and capacitive signals at three different locations on the upper surface of the teeth; (F) Triboelectric and capacitive signals of four occlusion conditions; (G) Triboelectric and capacitive signals at different occlusion speeds; (H) Confusion matrix for occlusion type recognition (accuracy analysis); (I) Comparison of occlusion recognition accuracy of LSTM, MLP, and 1D-CNN models; (J) Loss and accuracy variation characteristics during model training; (K) Practical application demonstration of the oral occlusion recognition system. Detailed Implementation

[0026] This invention utilizes a gelatin-based composite hydrogel system, combining the triboelectric effect and the double-layer sensing principle of ion supercapacitors to construct a five-layer integrated stacked flexible composite structure. This structure forms a collaborative working mechanism of triboelectric non-contact motion sensing and ion pressure contact detection, enabling the fabrication of a dual-function oral flexible sensor capable of simultaneously monitoring mandibular movement trajectory and occlusal force. By adjusting the proportions and surface microstructure of functional fillers such as MXene, ionic liquids, and PEDOT:PSS, high-precision synchronous acquisition of motion and pressure signals in oral environments is achieved. Furthermore, by optimizing the hydrogel formulation, the material is endowed with excellent water retention, self-healing properties, adhesion, and biocompatibility, meeting the requirements for long-term use in the high-humidity environment of the oral cavity.

[0027] 1) Example 1: Preparation method of spacer layer hydrogel (SLH) A) Raw material mixing: Add 0.46g sodium chloride, 3g glycerol and 4g deionized water to a beaker and stir magnetically at 1000 rpm for 30 min at room temperature; then add 2g gelatin and let it stand to swell for 2 h; then place it in a 75 ℃ water bath and stir magnetically at 3000 rpm for 1 h to mix evenly to obtain the spacer layer hydrogel precursor solution; B) Injection molding: Pour the above-mentioned precursor liquid into a square frame mold, level it with a scraper, and freeze-solidify it in an environment of -20 ℃ for 60 min; C) Demolding process: After complete curing, demold to obtain a rectangular ring-shaped spacer hydrogel SLH.

[0028] 2) Example 2: Preparation method of triboelectric layer hydrogel TLH A) Raw material mixing: Take 0.46g sodium chloride, 3g glycerol, and 4g Ti3C2T (8% by mass). x Add the (MXene) aqueous dispersion to a beaker and stir magnetically at 1000 rpm for 30 min at room temperature; then add 2 g of gelatin and let it stand to swell for 2 h; then place it in a 75 ℃ water bath and stir magnetically at 3000 rpm for 1 h to mix evenly. B) Ultrasonic dispersion: The mixed solution was placed in an ice-water bath and ultrasonically treated with 500 W power for 12 min (1.5s on, 2s off) to ensure uniform dispersion of MXene sheets and obtain the triboelectric layer hydrogel precursor solution. C) Molding and Microstructure Construction: Pour the precursor liquid into a flat mold with dimensions of 2cm×3cm×0.01cm, level it with a scraper, lay a 100-mesh screen to construct the surface mesh microstructure, and freeze-cure it in an environment of -20℃ for 60 min; D) Demolding treatment: After curing, demold to obtain a triboelectric layer hydrogel (TLH) with a network microstructure.

[0029] 3) Example 3: Preparation method of UELH hydrogel for upper electrode layer A) Raw material mixing: Take 0.46g sodium chloride, 3g glycerol, 2g PEDOT:PSS solution, and 2g 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-BF6, 98%) and add them to a beaker. Stir magnetically at 1000 rpm for 30 min at room temperature. Then add 2g gelatin and let it stand to swell for 2 h. Then place it in a 40 ℃ water bath and stir magnetically at 3000 rpm for 1 h to mix evenly to obtain the electrode layer hydrogel precursor solution. B) Molding and Microstructure Construction: Pour the precursor liquid into a flat mold with dimensions of 2cm×3cm×0.01cm, level it with a scraper, and lay a 250-mesh screen to construct a surface mesh microstructure; place it in an environment of -20 ℃ for freeze curing for 60 minutes; C) Demolding process: After curing, demold to obtain the upper electrode layer hydrogel UELH.

[0030] 4) Example 4: Preparation method of electrolyte layer hydrogel EYLH A) Raw material mixing: Take 0.46g sodium chloride, 3g glycerol, 2g deionized water, and 2g 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-BF6, 98%) and add them to a beaker. Stir magnetically at 1000 rpm for 30 min at room temperature. Then add 2g gelatin and let it stand to swell for 2 h. Then place it in a 50 ℃ water bath and stir magnetically at 3000 rpm for 1 h to mix evenly. The volume ratio of ionic liquid in the electrolyte layer hydrogel precursor solution is 20%. B) Injection molding and microstructure construction: Pour the precursor liquid into a flat mold with dimensions of 2cm×3cm×0.01cm, smooth it with a scraper, and construct a mesh microstructure on the upper and lower surfaces using screen printing technology; freeze-cure at -20 ℃ for 60 min. C) Demolding process: After curing, demold to obtain electrolyte layer hydrogel EYLH.

[0031] 5) Example 5: Preparation method of LELH hydrogel for the lower electrode layer A) Raw material mixing: The process parameters such as raw material ratio, stirring speed, stirring temperature, swelling time and so on are completely consistent with those in Example 3. After uniform mixing, the hydrogel precursor liquid of the lower electrode layer is obtained. B) Molding and Microstructure Construction: Pour the precursor liquid into a flat mold with dimensions of 2cm×3cm×0.01cm, level it with a scraper, and lay a 250-mesh screen to construct a surface mesh microstructure; place it in an environment of -20 ℃ for freeze curing for 60 minutes; C) Demolding process: After curing, demold to obtain the lower electrode layer hydrogel LELH.

[0032] 6) Assembly of a dual-function oral flexible sensor: A) Layer stacking: The triboelectric layer hydrogel TLH, the upper electrode layer hydrogel UELH, the spacer layer hydrogel SLH, the electrolyte layer hydrogel EYLH, and the lower electrode layer hydrogel LELH are stacked tightly in sequence from top to bottom, and the interlayer bonding and fixation are achieved by relying on the adhesion of the hydrogel itself. B) Electrode and lead assembly: Take two 2cm×3cm silver electrodes with a thickness of 0.01mm and attach them to the outermost side of the overall gel structure. Lead out a 0.1mm diameter silver signal wire from the silver electrodes. C) Encapsulation and curing: The entire device is sealed and encapsulated with a 0.04mm thick biocompatible flexible waterproof membrane and placed in a constant temperature chamber at 45℃~50℃ for 8 minutes to allow the encapsulation membrane to fully cure, ultimately obtaining a hydrogel-based oral flexible sensor for triboelectric-ion pressure.

[0033] The performance of the flexible dual-functional sensor prepared in this application will be tested below. (1) Figure 1 shows the structure and sensing mechanism of the dual-function flexible sensor. Based on the multi-layer stacked structure of gelatin-based composite hydrogel (triboelectric layer + upper electrode layer + spacer layer + electrolyte layer + lower electrode layer), it can simultaneously realize the dual functions of triboelectric non-contact motion sensing and ion supercapacitor pressure response. The purpose of the experiment is to clarify the design principle and dual-mode collaborative sensing mechanism of the multi-layer composite structure of the present invention. Specifically, the functional hydrogel layers prepared in the examples are selected as representatives. MXene-doped triboelectric layer hydrogel TLH, ionic liquid / PEDOT:PSS composite upper / lower electrode layer hydrogel UELH / LELH, sodium chloride gelatin spacer layer hydrogel SLH, and ionic liquid-doped electrolyte layer hydrogel EYLH are prepared respectively. Based on the material composition and microstructure characteristics, the molecular network and ion transport path of each hydrogel layer are drawn (Figure 1). The signal response mechanism of each layer under dynamic friction and pressure is analyzed respectively. The experimental results show that the triboelectric unit, composed of the triboelectric layer TLH and the upper electrode layer UELH, can generate electrical signals through dynamic contact separation, enabling non-contact detection of mandibular movement trajectories. The ion pressure unit, composed of the upper electrode layer UELH, the spacer layer SLH, the electrolyte layer EYLH, and the lower electrode layer LELH, can generate capacitance signals through ion migration and double-layer changes under pressure, enabling quantitative detection of occlusal force. These dual-mode synergistic sensing mechanisms are stably coupled in the multilayer structure, providing core mechanistic support for the synchronous monitoring of intraoral movement and pressure.

[0034] (2) Figure 2 shows the preparation and characterization results of the substrate material. The gelatin-based composite hydrogel can be precisely controlled by doping with different functional fillers, and each layer of the material has excellent structural uniformity and interfacial compatibility. The purpose of the experiment was to verify the feasibility of the preparation process of the hydrogel material and to characterize the microstructure and elemental distribution characteristics of each functional layer. In the preparation process verification experiment, five functional hydrogels, namely SLH, TLH, UELH, EYLH and LELH, were prepared based on sodium chloride, glycerol and gelatin, respectively, corresponding to the material systems of Examples 1 to 5. The macroscopic morphology observation, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to characterize each layer of hydrogel. The experimental results are as follows: each layer of hydrogel exhibits a uniform transparent or uniformly doped macroscopic morphology. The TLH surface shows uniformly distributed MXene particles, and the EYLH cross-section reveals a continuous three-dimensional network structure. EDS spectroscopy shows that C, N, O, and F elements are uniformly distributed in the TLH, indicating good dispersion of MXene in the hydrogel. The interfaces between the hydrogel layers are tightly bonded, with no obvious delamination. The gelatin-based composite hydrogel prepared in this application has a stable process, and the materials of each functional layer exhibit good homogeneity and interfacial compatibility, providing a reliable material basis for device integration.

[0035] (3) Figure 3 shows the performance characterization results of the triboelectric unit. The output voltage of the triboelectric unit can reach 0.2V, and the signal attenuation rate is less than 5% after 10,000s of continuous cycling. The output signal is stable under different frequencies and different friction materials. The purpose of the experiment is to verify the working mechanism of the triboelectric unit and evaluate its output performance, stability and anti-interference ability. In the triboelectric performance test, a linear motor test platform was used to conduct contact-separation tests on the triboelectric unit composed of TLH and UELH, and the output current, charge and voltage curves were recorded. The change law of the output signal was tested by changing the contact distance, motion frequency and friction material. The long-term stability was evaluated by 10,000s continuous cycle test. The experimental results are as follows: the triboelectric unit can generate stable current, charge and voltage signals during the contact-separation process, and the peak output voltage can reach 0.2V; the output voltage decreases linearly with the increase of contact distance and remains stable with the increase of motion frequency; the comparison of different friction materials shows that the output performance of TLH is the best; in the continuous 10,000s cycle test, the voltage signal has no obvious attenuation and the stability is excellent. The triboelectric unit of this application has good output performance and strong anti-interference ability, and can stably realize non-contact detection of mandibular movement trajectory.

[0036] (4) Figure 4 shows the performance characterization results of the ion pressure unit. The sensitivity of the ion pressure unit is 4.97 kPa in the pressure range of 10~40 kPa. -1The response time was 1 s, the recovery time was 1.6 s, and the capacitance signal drift was less than 10% after 1000 pressure cycles. The experiment aimed to verify the working mechanism of the ion pressure unit and evaluate its sensitivity, response speed, and cycle stability. In the ion pressure performance test, different pressures were applied to the ion pressure unit composed of UELH-SLH-EYLH-LELH, and the capacitance change rate was recorded. By comparing the performance with and without a spacer layer, different ion liquid concentrations, and different surface microstructures, the sensor unit design was optimized. The response characteristics and cycle stability were tested by applying dynamic loads of different frequencies and pressures. The experimental results showed that the introduction of the spacer layer significantly improved the low-pressure response performance; the sensor unit had the highest sensitivity at an ion liquid doping concentration of 20%; and the surface microstructure could further enhance the pressure response. The ion pressure unit achieved a sensitivity of 4.97 kPa in the 10–40 kPa range. -1 The response time is 1 second, the recovery time is 1.6 seconds, and the dynamic response curve shows no significant hysteresis. After 1000 pressure cycle tests, the capacitance change rate curve shows good repeatability, and the signal drift is less than 10%. The ion pressure unit of this application has high sensitivity, fast response speed, and excellent cycle stability, and can accurately realize the quantitative detection of biting force.

[0037] (5) Figure 5 shows a practical application demonstration of the oral occlusion sensing system. The system can simultaneously collect mandibular movement trajectory and occlusal force signals. The recognition accuracy of four types of occlusal postures—normal occlusion, left occlusion, right occlusion, and anterior crossbite—reaches 99.25%, with a response delay of less than 0.5s. The purpose of the experiment was to verify the practical application capability of the dual-function sensing system in oral scenarios and to evaluate the accuracy and real-time performance of occlusal posture recognition. The experimental process involved attaching three sets of dual-function flexible sensors to the surface of the dental table to construct an intraoral sensing array; collecting triboelectric and capacitive signals under different open bite / occlusal movements, different occlusal positions, and different occlusal speeds; constructing a 1D-CNN model to train and test the recognition of the four types of occlusal postures; and demonstrating the real-time monitoring capability of the system through actual occlusal scenarios. Experimental results show that the system can synchronously output stable triboelectric and capacitive signals, corresponding to the mandibular movement trajectory and occlusal force changes, respectively; the signal characteristics under different occlusal positions and occlusal speeds are significantly different and can be effectively distinguished; the 1D-CNN model achieves a recognition accuracy of 99.25% for the four types of occlusal postures, significantly outperforming LSTM and MLP models; the system can display the occlusal signal waveform and output the recognition results in real time, with a response delay of less than 0.5s. This dual-function oral sensing system exhibits stable signal acquisition, high recognition accuracy, and good real-time performance, and can be applied to clinical scenarios such as temporomandibular joint disease diagnosis and prosthesis restoration evaluation, demonstrating good practical application value and industrialization prospects.

[0038] The embodiments described herein are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a hydrogel-based flexible oral sensor based on triboelectric-ionic pressure, characterized in that: Includes the following steps: S1. Preparation of hydrogels for each functional layer a. Preparation of SLH (Separator Layer Hydrogel) raw materials: Sodium chloride and glycerol were added to deionized water and magnetically stirred at 1000 rpm for 30 min at room temperature. Then gelatin was added and allowed to swell for 2 h. The mixture was then placed in a 75 ℃ water bath and stirred continuously at 3000 rpm for 1 h to obtain a uniform and transparent gel precursor solution. The mass ratio of sodium chloride, glycerol, gelatin and deionized water was 0.46:3:2:

4. b. Preparation of Triboelectric Layer Hydrogel (TLH) Raw Materials: Following the basic formulation of the spacer layer hydrogel, replace deionized water with 8% (w / w) MXene (Ti3C2T). x Aqueous dispersion was prepared, with the proportions of other materials, stirring temperature, and stirring speed maintained at the same level. After stirring, the mixture was ultrasonically treated in an ice-water bath to obtain the triboelectric layer gel precursor solution. The optimal doping ratio of MXene to gelatin was 8%. c. Preparation of UELH hydrogel raw materials for the upper electrode layer: According to the basic formula of the spacer layer hydrogel, replace the deionized water with an equal volume of PEDOT:PSS solution and BMIM-BF6 ionic liquid mixture, and stir magnetically at 40 ℃ until the system is homogeneous to complete the preparation of the precursor solution; wherein, the volume ratio of polyurethane matrix, PEDOT:PSS and ionic liquid is 2:1:1; d. Preparation of Electrolyte Layer Hydrogel (EYLH): Following the basic formulation of the spacer layer hydrogel, replace deionized water with an equal volume of deionized water and ionic liquid BMIM-BF6. Mix thoroughly with magnetic stirring at 50 °C to obtain the electrolyte layer gel precursor solution; the total volume of ionic liquid accounts for 20% of the solvent in the system. e. Preparation of raw materials for the lower electrode layer hydrogel LELH: The raw material ratio, stirring process and parameters are exactly the same as in step c, to obtain the lower electrode layer gel precursor solution; f. Functional hydrogel molding and microstructure construction: The spacer layer gel precursor liquid was injected into a square frame structure mold, and after freezing and solidification, it was demolded to obtain a rectangular ring structure spacer layer hydrogel SLH; TLH, UELH, EYLH and LELH precursor liquids were injected into a flat mold respectively, and a network microstructure was constructed on the gel surface using screen printing technology. After low-temperature freezing and solidification, it was demolded to obtain the corresponding functional hydrogel films. S2. Assembly of the dual-function flexible sensor The triboelectric layer hydrogel TLH, the upper electrode layer hydrogel UELH, the spacer layer hydrogel SLH, the electrolyte layer hydrogel EYLH, and the lower electrode layer hydrogel LELH prepared in step S1 are stacked tightly from top to bottom, and the interlayer bonding and fixation are achieved by the self-adhesion of the hydrogels. Silver wires are led out from the upper and lower electrode layers as signal output terminals. Finally, the whole is encapsulated with a biocompatible flexible waterproof membrane and cured by heat preservation to obtain a triboelectric-ion pressure dual-function oral flexible sensor.

2. The preparation method according to claim 1, characterized in that: In steps S1b-S1d, the ionic liquid used is 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-BF6), and the two-dimensional packing material is Ti3C2T. x MXene.

3. The preparation method according to claim 1, characterized in that: In step S1a, sodium chloride and glycerin are used as functional additives, with the mass ratio of sodium chloride to gelatin being 0.23:1 and the mass ratio of glycerin to gelatin being 1.5:

1.

4. The preparation method according to claim 1, characterized in that: In step S1b, the ultrasonic treatment conditions are as follows: 500W power ultrasonic treatment for 12 minutes, ultrasonic treatment for 1.5 seconds, pause for 2 seconds, and the entire process is carried out in an ice water bath environment.

5. The preparation method according to claim 1, characterized in that: In step S1f, the freeze-curing temperature is -20 ℃ and the curing time is 60 min; the mesh count of the screen used for screen printing is 100 mesh to 250 mesh.

6. The preparation method according to claim 1, characterized in that: In step S2, the diameter of the silver wire is 0.1 mm and the thickness of the biocompatible flexible waterproof membrane is 0.04 mm.

7. The preparation method according to claim 1, characterized in that: In step S2, the curing conditions after encapsulation are: constant temperature holding at 45℃~50℃ for 8 min~12 min.

8. A hydrogel-based flexible oral sensor for triboelectric-ionic pressure prepared by any of the preparation methods described in claims 1-7.

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