Strain-insensitive flexible transparent stretchable temperature sensor and preparation method and application thereof

Abstract

The invention belongs to the technical field of flexible electronic devices, and particularly relates to a strain-insensitive flexible transparent stretchable temperature sensor and a preparation method and application thereof. The sensor is of a sandwich structure and comprises flexible transparent stretchable electrodes on the two sides and a transparent ionic gel electrolyte layer clamped between the flexible transparent stretchable electrodes. The electrode is an AgNWs / MXene / AgNWs sandwich structure composite electrode which is constructed on a pre-stretched PDMS (Polydimethylsiloxane) elastic substrate and has a wrinkle structure; and the electrolyte layer is a PAT ionic gel layer. The MXene material is introduced to regulate and control the surface potential of the electrode, and the constructed folded electrode structure is utilized to effectively release the strain, so that the sensor has the characteristics of high temperature sensitivity and excellent strain insensitivity, and meanwhile, the sensor has a wide working temperature range, high optical transparency and a stable electrode-electrolyte interface; the method can be widely applied to the fields of human health monitoring, intelligent artificial limb interaction, temperature sensing arrays and the like.

Description

Technical Field

[0001] This invention belongs to the field of flexible electronic device technology, specifically relating to a strain-insensitive flexible transparent stretchable temperature sensor, its preparation method, and its application. Background Technology

[0002] Flexible temperature sensors are wearable devices that can be directly attached to the surface of human skin or curved surfaces. They can be used to detect the local temperature of a living organism or the temperature of external contact. They output temperature information by collecting electrical signal parameters such as resistance R, voltage U, current I, and capacitance C. To ensure the accuracy and stability of data measurement and meet the needs of practical applications, flexible temperature sensors usually need to have two core characteristics: (1) excellent temperature sensing performance, specifically including high sensitivity, high precision, fast response rate, good repeatability, a certain temperature detection range, and excellent anti-environmental interference ability; (2) suitable material properties, requiring the sensor material to be thin, flexible, biocompatible, and have excellent toughness and fatigue resistance. Currently commercially available traditional temperature sensors, such as infrared temperature sensors, resistance temperature detectors, fiber optic temperature sensors, and electronic thermometers, generally have the problem of large size and mostly use hard semiconductors, metals, and other materials, which cannot meet the needs of wearable use. In contrast, flexible temperature sensors are lightweight, can adapt to the deformation of human skin, and have both biocompatibility and wearing comfort.

[0003] Flexible temperature sensors typically utilize the temperature dependence of the motion of ions, electrons, and dipoles within the sensing material to achieve sensing functionality. Among resistive, thermoelectric, and pyroelectric temperature sensing principles, capacitive sensing mechanisms have attracted widespread attention due to their advantages of fast response, no drift, high sensitivity, and high resolution. The sensing mechanism of double-layer capacitive flexible temperature sensors is based on the physical properties of the electric double-layer (EDL). Essentially, temperature affects ion transport performance and the amount of ions adsorbed at the double layer, thus causing changes in the electric double-layer capacitance (EDLC). This principle has been confirmed by numerous studies through experiments and theoretical calculations. Currently, flexible temperature sensors face two major challenges: first, strain leads to changes in their sensing performance, a challenge that urgently needs to be overcome; second, there is a lack of research reports on the impact of electrode structure on the performance of double-layer temperature sensors. Problems such as low sensitivity, large strain interference, and narrow temperature range in existing technologies also need to be addressed. In addition, there is a strong demand for transparent flexible temperature sensors in fields such as displays and electronic skin, but there are also few reports on highly transparent flexible temperature sensors.

[0004] In summary, there is an urgent need to develop a strain-insensitive, flexible, transparent, and stretchable temperature sensor. This sensor must be able to adapt to the deformation of human skin, possess biocompatibility and wearability comfort, and simultaneously meet the performance requirements of fast response, no drift, high sensitivity, and high resolution to address technical challenges such as narrow temperature range. Summary of the Invention

[0005] Flexible temperature sensors are lightweight and adaptable to the deformation of human skin, possessing biocompatibility and wearability comfort. They also feature fast response, no drift, high sensitivity, and high resolution. However, current flexible temperature sensors still suffer from low sensitivity, large strain interference, and narrow temperature range. Therefore, this invention provides a double-layer capacitive flexible stretchable temperature sensor with high sensitivity, strain insensitivity, wide operating temperature range, interface stability, and optical transparency.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of the present invention provides a strain-insensitive flexible transparent stretchable temperature sensor, wherein the temperature sensor adopts a three-layer structure design, consisting of PDMS-AMA composite electrodes on both sides and an ion gel electrolyte layer in the middle. The PDMS-AMA composite electrode uses PDMS elastomer as a flexible substrate, with AMA conductive components attached to the substrate surface. The AMA conductive components consist of two layers of one-dimensional (1D) AgNWs (silver nanowires) and one layer of two-dimensional (2D) MXene material, with the two-dimensional (2D) MXene material located in the middle and the two layers of one-dimensional (1D) AgNWs (silver nanowires) located on both sides of the MXene material. The ion gel electrolyte layer is a PAT ion gel layer.

[0007] The second aspect of the present invention also provides a method for fabricating the strain-insensitive flexible transparent stretchable temperature sensor described in the first aspect, the method comprising the following steps: S1. Preparation of PDMS-AMA composite electrode by pre-stretching spin coating method: After uniaxial pre-stretching and fixing of PDMS elastomer, surface modification is performed by Plasma air plasma treatment. Then, three layers of conductive material are spin-coated in the order of AgNWs, MXene, and AgNWs. The pre-stretching is then released and the residual solvent is removed to obtain the PDMS-AMA composite electrode. The thickness of the PDMS-AMA composite electrode is 10-20 μm. S2. Preparation of the ion gel electrolyte layer: Acrylamide (AAm) monomer, 2,2,2-trifluoroethyl acrylate (TFEA) monomer, I2959 photoinitiator and [EMIM]TFSI ionic liquid are prepared into a homogeneous transparent solution. After deoxygenation treatment, the mixture is injected into a mold consisting of two demolded substrates and a spacer between the substrates, and then cured with ultraviolet light to obtain the PAT ion gel layer. The thickness of the PAT ion gel layer is 100-200 μm. S3. Adhere the conductive surface of the PDMS-AMA composite electrode of S1 to the upper and lower surfaces of the PAT ion gel of S2, and leave conductive surfaces on the left and right sides of the upper and lower electrodes for lead wires. Finally, after encapsulation, the temperature sensor is obtained.

[0008] This invention designs and fabricates a flexible, transparent, double-layer capacitive strain-insensitive temperature sensor (AMA-PAT) that is flexible, interface-stable, resistant to high and low temperatures, and optically transparent. The sensor employs a three-layer structure: stretchable transparent electrodes (PDMS-AMA) on both sides, with the conductive components of the electrodes consisting of two layers of AgNWs sandwiching a middle MXene layer, and an ionogel (PAT) electrolyte layer in the center. Through electrode material and structural design, this invention achieves a high sensitivity of 3.55 % / ℃ and strain insensitivity in the temperature sensor. Furthermore, by constructing a 4×4 sensor array, the application value of the AMA-PAT flexible temperature sensor in human health monitoring, object motion recognition, bionic intelligent prosthetic interaction, and high and low temperature prevention is demonstrated.

[0009] Preferably, in S1, the PDMS elastomer is subjected to 40%-60% uniaxial pre-stretching.

[0010] Preferably, in S1, the pressure of the plasma treatment is 7-15 Pa, the power is 15-30 W, and the time is 4-7 min.

[0011] Preferably, in S1, before spin coating, AgNWs is prepared into a solution of 1-3 mg / mL and MXene is prepared into a solution of 1-2 mg / mL; the spin coating speed is 800-1500 rpm and the time is 50-70 s; after each spin coating, it is necessary to dry at 35-50℃ for 1-2 min to remove some of the solvent.

[0012] Preferably, in S1, the PDMS elastomer is a PDMS film, which is prepared by the sacrificial layer method: prepare 8-15 wt% PVA solution and PDMS stock solution, first spin-coat 2 layers of PVA on a glass substrate to form a PVA sacrificial layer; then spin-coat 1 layer of PDMS film, and after dissolving and removing the PVA sacrificial layer, a PDMS film with a thickness of 10-50 μm is obtained.

[0013] More preferably, when spin coating PVA, the rotation speed is 800-1500 rpm and the time is 30-50 s; when spin coating PDMS, first spin coating at a speed of 400-700 rpm for 7-15 s, and then spin coating at a speed of 3000-6000 rpm for 50-100 s.

[0014] More preferably, after spin-coating PDMS, it is cured at 70-80°C for 1-3 hours to form a PDMS thin film layer.

[0015] Preferably, in S1, the MXene is Ti3C2T. x MXene is prepared using Ti3AlC2 as the MAX phase raw material through a four-step process of etching, washing, intercalation, and freeze-drying. The specific preparation method is as follows: S11. Etching: Dissolve LiF in concentrated hydrochloric acid to form an etching solution, then add Ti3AlC2, and react at 30-50℃ for 40-60h to obtain the etching reaction solution. S12. Washing: Pour off the supernatant of the etching reaction solution, take the precipitate and wash it with water by centrifugation multiple times, gradually increasing the speed from 1000 rpm to 3500 rpm until the pH of the solution after washing is >4. Discard the supernatant to obtain mud-like multilayer MXene. S13, Intercalation: Multilayer MXene is dispersed in water and ultrasonically treated under an inert atmosphere to achieve intercalation of water molecules between MXene sheets. The supernatant is then collected by centrifugation to obtain an MXene aqueous solution. S14. Freeze-drying: After pre-freezing the MXene aqueous solution, freeze-drying is performed to obtain foamy Ti3C2T. x MXene solid.

[0016] Preferably, in S2, the molar ratio of the acrylamide monomer to the 2,2,2-trifluoroethyl acrylate monomer is 1-2:2-3; the amount of the I2959 photoinitiator is 0.1-1 wt% of the total mass of the monomer system; and the amount of the [EMIM]TFSI ionic liquid is 50-70 wt% of the total mass of the mixture.

[0017] Preferably, in step S2, the power of the ultraviolet curing is 1-4 mW / cm². 2 The time is 1-4 hours.

[0018] The third aspect of the present invention also provides applications of the strain-insensitive flexible transparent stretchable temperature sensor described in the first aspect, including human health monitoring, intelligent prosthetic interaction, or temperature sensing arrays.

[0019] Compared with the prior art, the beneficial effects of the present invention are: This invention discloses a strain-insensitive flexible, transparent, and stretchable temperature sensor and its fabrication method. The sensor employs a sandwich structure, comprising flexible, transparent, and stretchable electrodes on both sides and a transparent ionomer gel electrolyte layer sandwiched in the middle. The electrodes are AgNWs / MXene / AgNWs sandwich structure composite electrodes with a wrinkled structure constructed on a pre-stretched PDMS elastic substrate; the electrolyte layer is a PAT ionomer gel copolymerized from acrylamide and trifluoroethyl acrylate using a hydrophobic ionic liquid as a solvent. This invention modulates the electrode surface potential by introducing MXene material and effectively releases strain using the constructed wrinkled electrode structure, enabling the sensor to possess both high temperature sensitivity (up to 3.55% / ℃ in the 25-55℃ range) and excellent strain insensitivity (capacitance change rate <6% at 0-50% strain). Simultaneously, the sensor exhibits a wide operating temperature range (-35℃ to 70℃), high optical transparency (>76.5%), and a stable electrode-electrolyte interface, making it widely applicable in fields such as human health monitoring, intelligent prosthetic interaction, and temperature sensing arrays. Attached Figure Description

[0020] Figure 1 The diagram shows the sensor structure. The enlarged view shows the AgNWs / MXene / AgNWs (AMA) sandwich structure composite electrode attached to PDMS.

[0021] Figure 2 The mechanical properties of different devices, including PAT ion gel, PDMS-AMA electrode and AMA-PAT sensor, are shown in (a) stress-strain curves; (b) elastic modulus, fracture strength and elongation at break; and (c) maximum strain of PDMS prepared with different pre-stretching.

[0022] Figure 3 Optical performance of different devices; including (a) UV transmission spectra of PAT ion gel, PDMS-AMA electrode, and AMA-PAT sensor, with an inset of a photograph of the sensor on the school emblem image; and (b) SAXS curve of PAT ion gel.

[0023] Figure 4 The AMA-PAT sensor is evaluated for (a) temperature detection sensitivity, (b) temperature response recovery performance, and (c) wide temperature range response capability.

[0024] Figure 5 Temperature sensing stability of the AMA-PAT sensor; including (a) 30-40 (a) 5 heating cycles; (b) 30-40 The heating-cooling cycle curve.

[0025] Figure 6The strain insensitivity properties of the AMA-PAT sensor include (a) the relationship between capacitance and strain, and (b) the relationship between the relative capacitance change rate and temperature at different strains (0%, 25%, 50%).

[0026] Figure 7 Morphological characterization of the PDMS-AMA electrode; (a) scale bar is 10 μm; (b) scale bar is 2 μm; (c) scale bar is 300 nm.

[0027] Figure 8 Adhesion performance of the device. (a) Interfacial adhesion strength between PDMS and PDMS-AMA electrodes and PAT ion gel; (b) Schematic diagram of adhesion force test: PAT ion gel, adhesion substrate (PDMS or PDMS-AMA electrode), and rigid glass substrate are assembled according to the structure shown in the figure to form a test sample containing the adhesion interface. Then, the sample is separated at the adhesion interface. The interfacial adhesion strength can be obtained by measuring the force required to separate the interface.

[0028] Figure 9 The conductivity of PAT ion gel includes (a) impedance and (b) the relationship between ionic conductivity and temperature.

[0029] Figure 10 For temperature sensor applications in human health monitoring.

[0030] Figure 11 For the application of temperature sensor in intelligent prosthetic interaction and temperature sensor array, including (a) the initial appearance of the AMA-PAT flexible temperature sensor array after it is attached to the back of the simulated prosthetic hand, (b) the process of the human hand shaking hands with the prosthetic hand with the sensor array attached, simulating the action of actual human-computer interaction, (c) the capacitance change rate distribution of each area of ​​the sensor array after shaking hands, and (d) the temperature distribution of each area of ​​the sensor array after shaking hands. Detailed Implementation

[0031] The specific embodiments of the present invention will be further described below. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0032] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the experimental materials used in the following embodiments are all available through conventional commercial channels.

[0033] Example: A double-layer capacitive flexible stretchable temperature sensor (AMA-PAT) and its fabrication method 1. This flexible temperature sensor adopts a three-layer structure design, consisting of electrodes on both sides and an electrolyte layer in the middle. Its structural diagram is shown below. Figure 1 As shown. The core components of the flexible temperature sensor are as follows: (1) The electrodes on both sides are AgNWs / MXene / AgNWs sandwich structure composite electrodes (PDMS-AMA), constructed on a pre-stretched PDMS elastic substrate, and are in a wrinkled shape; and the electrodes are stretchable electrodes (see structure). Figure 1 The illustration on the right shows a structure made with PDMS elastomer as a flexible substrate, onto which an AMA conductive component is attached. The AMA conductive component consists of two layers of one-dimensional (1D) AgNWs (silver nanowires; purchased from Zhongke Leiming (Beijing) Technology Co., Ltd.) and one layer of two-dimensional (2D) MXene material, with the two-dimensional (2D) MXene material located in the middle and the two layers of one-dimensional (1D) AgNWs (silver nanowires) located on both sides of the MXene material. This conductive component structure with an intermediate MXene layer is beneficial for improving temperature detection sensitivity.

[0034] (2) The electrolyte layer in the middle is PAT ion gel, which is made by copolymerizing acrylamide and trifluoroethyl acrylate with hydrophobic ionic liquid as solvent.

[0035] 2. Fabrication of flexible temperature sensors: (1) Preparation of flexible stretchable substrate (PDMS thin film) by sacrificial layer method, the specific preparation method is as follows: First, prepare a 10 wt% PVA (polyvinyl alcohol) solution and a PDMS stock solution (PDMS component A (base) and component B (curing agent) (Dow Corning 184) mixed at a volume ratio of 15:1). Two layers of the PVA solution are spin-coated onto a clean glass substrate (76 mm × 26 mm) (1000 rpm for 40 s each time), and dried to form a PVA sacrificial layer. Then, a layer of the PDMS stock solution is spin-coated (500 rpm for 10 s first, then 4000 rpm for 60 s), and cured at 80°C for 2 h to form a PDMS film. Finally, the PVA sacrificial layer is dissolved and removed in deionized water, yielding a PDMS film with a thickness of approximately 15 μm.

[0036] (2) A flexible and stretchable PDMS-AMA composite electrode was prepared by pre-stretch spin coating (the conductive component materials of the electrode were all prepared by spin coating, which can form a micron-thick film and improve the uniformity of the conductive layer): After 50% uniaxial pre-stretching and fixing of the PDMS film, surface modification was performed using plasma treatment (10 Pa, 20 W, 5 min) to obtain a wrinkled structure and to modify the hydrophobic surface to facilitate the uniform distribution of conductive materials. Three layers of conductive materials were then spin-coated sequentially onto one side of the treated PDMS in the order of AgNWs, MXene, and AgNWs. Each material was spin-coated at 1000 rpm for 60 s (AgNWs: 2 mg / mL, MXene: 1 mg / mL). After each spin-coating, the film was dried at 40°C for 1 min to remove some solvent, allowing the conductive materials to adhere more firmly to the substrate surface. Finally, the pre-stretching was slowly released, and the film was placed in a vacuum oven at 50°C overnight to remove residual solvent, resulting in a flexible, stretchable composite electrode (PDMS-AMA) with a wrinkled surface. The thickness of the conductive component was approximately 15 μm (approximately 5 μm per conductive layer).

[0037] Among them, MXene (Ti3C2T) x The preparation of MXene is as follows: 1) Etching: A fluoride-hydrochloric acid solution etching method was adopted, with Ti3AlC2 as the MAX phase and lithium fluoride (LiF) and hydrochloric acid as etching solvents. First, 30 mL of 9 mol / L concentrated hydrochloric acid (36 wt%) was weighed and poured into a polytetrafluoroethylene (PTFE) reactor, followed by the addition of 1.98 g of LiF. The solution was dissolved at room temperature for 5 min, and then 1 g of Ti3AlC2 was slowly added. After mechanical stirring for 30 min, the etching stock solution was obtained. Finally, the etching reaction was carried out at 40 °C for 45 h.

[0038] 2) Washing: Pour off the supernatant and centrifuge the precipitate obtained after the reaction 10 times with deionized water as solvent, with the speed gradually increasing from 1000 rpm to 3500 rpm until the solution pH>4. Then pour off the supernatant to obtain multi-layered MXene in the form of mud-like precipitate.

[0039] 3) Intercalation: Add 150 mL of deionized water, shake to mix and disperse the precipitate in the aqueous solution, continue stirring for 20 min to ensure uniform dispersion, then sonicate the MXene solution under Ar atmosphere for 1 h to achieve water molecule intercalation between MXene sheets (gas replacement for 20 min before sonication). Centrifuge the sonicated suspension at 3500 rpm for 1 h, collect the supernatant to obtain an MXene aqueous solution of a certain concentration. Take 4 mL of the MXene aqueous solution for vacuum filtration using a polypropylene (PP) membrane. After filtration, dry the residue and weigh it, finally calculating the concentration (to prepare a 1 mg / mL MXene aqueous solution for the preparation of the conductive layer).

[0040] 4) Freeze-drying: First, freeze the MXene aqueous solution at -40℃ for 12 h, and then freeze-dry for 72 h to finally obtain foamy MXene solid.

[0041] (3) Preparation of PAT ion gel Using AAm (acrylamide, C3H5NO; CAS No.: 79-06-1) and TFEA (2,2,2-trifluoroethyl acrylate; CAS No.: 407-47-6) as monomers, I2959 as photoinitiator (CAS No.: 106797-53-9), and [EMIM]TFSI (CAS No.: 174899-82-2) as ionic liquid, 0.2843 g of AAm and 1.2327 g of TFEA (AAm:TFEA = 1:2 molar ratio) were weighed first, followed by the addition of 7.6 mg of I2959 photoinitiator (0.5 wt% of the total mass of the two monomers) and 2.2755 g of [EMIM]TFSI (60 wt% of the total mass of the two monomers). The mixture was stirred to form a homogeneous transparent solution, and then deoxygenated by passing Ar through it for 10 min. The solution was then injected between a glass plate and a PET sheet separated by a 150 μm silicone pad (both the glass plate and PET surfaces had been surface-treated to facilitate gel peeling), in a glove box environment, at 2 mW / cm². 2 PAT ionogel with a thickness of 150 μm was obtained by UV curing for 2 h.

[0042] (4) Fabrication of AMA-PAT double-layer capacitive flexible transparent stretchable temperature sensor: A 1.5 cm × 1 cm piece of PAT ion gel was cut, and the conductive surface of the PDMS-AMA composite electrode was bonded to the upper and lower surfaces of the PAT ion gel. A 2 mm wide conductive surface was left on the left and right sides of the upper and lower electrodes, respectively. Then, conductive tape was used as a connecting copper wire for electrical performance testing. Finally, the wire connection was encapsulated with PDMS to obtain the final AMA-PAT double-layer capacitive flexible temperature sensor.

[0043] Experimental Example: Device Performance Testing The prepared PAT, PDMS-AMA, and AMA-PAT flexible temperature sensors were tested for mechanical properties, optical properties, temperature sensing performance, strain insensitivity characteristics, and applications. (1) Mechanical properties: The tensile properties of the PDMS-AMA electrode, PAT ionogel, and AMA-PAT flexible temperature sensor were characterized using an electronic universal testing machine. Figure 2 As shown in a and 2b, AMA-PAT exhibits excellent tensile properties (elongation at break 180.3%) and an elastic modulus of 0.213 MPa, which is close to that of human skin, meeting the requirements for flexible wearable devices. Simultaneously, electrodes with a wrinkled surface structure were obtained through a pre-stretching method, and the surface morphology of the electrodes at different magnifications was characterized using field emission scanning electron microscopy. Figure 7 The near-parallel fold structure can be clearly observed. The introduction of this fold structure effectively improves the tensile strength of the electrode. Figure 2 c).

[0044] (2) Optical performance: The AMA-PAT device of this invention has high light transmittance, such as... Figure 3 As shown in the image, the emblem of Sun Yat-sen University can be clearly seen through the ionogel. Meanwhile, the UV-Vis absorption spectroscopy reveals that the AMA-PAT device has a transmittance exceeding 76.5% in the 450–850 nm range, and the absence of strong scattering or diffraction peaks detected by small-angle X-ray scattering (SAXS) confirms that no phase separation has occurred at the nanoscale.

[0045] (3) Temperature sensing performance: After fabricating a leaded AMA-PAT double-layer capacitive flexible temperature sensor, the temperature sensing performance of the device was tested using an LCR meter (100 Hz) combined with a semiconductor water-cooled temperature control platform. For example... Figure 4As shown, the device exhibits a temperature sensitivity of 3.55% / ℃ and a linear fitting accuracy of 0.998 within the temperature range of 25–55℃. The temperature sensing response time is approximately 36 s, and the recovery time is approximately 40 s. Furthermore, it demonstrates temperature response capability across a temperature range of -35 to 70℃. In addition, phased temperature data was collected within a fixed range (30–40℃) typical of human body contact temperatures, and the results are as follows. Figure 5 As shown, the sensor exhibits excellent repeatability, indicating its outstanding temperature sensing stability. This characteristic is closely related to the adhesion between the ionogel and the electrode: the ionogel itself has strong adhesion, and the superimposed wrinkled structure and conductive material result in an interfacial adhesion strength as high as 44.7 kPa (…). Figure 8 This high bonding strength allows the ion gel to form a reliable and stable interface with the electrode, maintaining a stable electric double layer even under arbitrary deformation, thus ensuring the reliability of the device's temperature sensing.

[0046] (4) Strain insensitivity: To investigate the strain response characteristics of the AMA-PAT double-layer capacitive flexible temperature sensor, its capacitance changes under different strains of 0%, 25%, and 50% were tested. Figure 6 As shown, the sensor exhibits excellent strain insensitivity: within the strain range of 0% to 50%, the capacitance change rate is less than 6%, remaining almost stable. This characteristic is presumably mainly due to the wrinkled structure introduced during the fabrication process. Further testing of the capacitance change with temperature under 0%, 25%, and 50% strain conditions revealed that the three curves almost completely overlap, fully confirming the strain insensitivity of the sensor's temperature sensing performance.

[0047] (5) Research on the double-layer temperature sensing mechanism of the device: When a 1 V AC voltage is applied across the electrode, the PDMS-AMA composite electrode adsorbs counterions from the PAT ion gel through electrostatic adsorption and van der Waals forces, thereby forming a charge-separated double layer. MXene, with its abundant surface functional groups (-F, -O, -OH), metallic conductivity, and thermal stability, optimizes the electrode performance; simultaneously, the designed wrinkled structure effectively increases the electrode's specific surface area, providing more sites for ion adsorption.

[0048] The temperature sensing characteristics of the device originate from the ion transport behavior of the ion gel at different temperatures, such as... Figure 9 As shown, with increasing temperature, the device impedance decreases and the ionic conductivity increases. At low temperatures, the charge density at the electric double layer is low; as temperature increases, on the one hand, the ion pairs [EMIM]... + [TFSI] -Increased dissociation leads to a greater number of independent cations and anions in the electrolyte, directly boosting ionic conductivity. On the other hand, weakened interionic interactions and increased polymer chain segment freedom reduce the binding effect of polymer chains on ions, increase the number of free vacancies for ion transfer, and ultimately enhance the amount of charge adsorbed on the electrode surface.

[0049] (6) To demonstrate that the sensor of this invention can be widely used in human health monitoring, intelligent prosthetic interaction, and temperature sensing arrays, the following experiments were also conducted: 1) Applications in human health monitoring: such as Figure 10 As shown, the AMA-PAT device was attached to the fingertip of the index finger. Its excellent flexibility and adhesion ensured good conformal contact with the skin. Using this sensor to detect the fingertip temperature at 25°C, the capacitance was measured to be 18.56 nF, corresponding to a calculated temperature of 27.73°C, which is highly close to the 27.6°C result displayed by the infrared thermal imager. This test result indicates that the device can be well applied to daily human health monitoring.

[0050] 2) Applications of intelligent prosthetic interaction and temperature sensor arrays: like Figure 11 As shown, a human-computer interaction scenario was constructed based on the AMA-PAT sensor: an AMA-PAT flexible temperature sensing array was attached to the back of a prosthetic hand to simulate the interaction process of shaking hands with a person. Test results show that the sensor's capacitance change rate and corresponding temperature distribution perfectly match the contact position of the finger on the array. Therefore, the contact area on the back of the prosthetic hand can be directly identified from the distribution map generated by the electrical signal, and the contact position can be located using temperature sensing, ultimately completing the human-computer interaction application.

[0051] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A strain-insensitive flexible transparent stretchable temperature sensor, characterized in that, The temperature sensor as a whole adopts a three-layer structure design and is composed of PDMS-AMA composite electrodes on both sides and an ionic gel electrolyte layer in the middle. The PDMS-AMA composite electrode takes a PDMS elastomer as a flexible substrate, and the surface of the substrate is attached with an AMA conductive component. The AMA conductive component is composed of two layers of one-dimensional AgNWs and one layer of two-dimensional MXene material, and the two-dimensional MXene material is located in the middle, and the two layers of one-dimensional AgNWs are located on both sides of the MXene material; and the ionic gel electrolyte layer is a PAT ionic gel layer.

2. The method of claim 1, wherein the strain-insensitive flexible transparent stretchable temperature sensor is prepared by, The method comprises the following steps: S1, pre-stretching a PDMS-AMA composite electrode by a spin coating method: after a PDMS elastomer is uniaxially pre-stretched and fixed, the surface is modified by air plasma treatment, then three layers of conductive materials are spin-coated in the order of AgNWs, MXene and AgNWs, and then the pre-stretching is released, and residual solvents are removed, so that the PDMS-AMA composite electrode is prepared, and the thickness of the PDMS-AMA composite electrode is 10-20 μm; S2, preparation of an ionic gel electrolyte layer: acrylamide monomer, 2,2,2-trifluoroethyl acrylate monomer, I2959 photoinitiator and [EMIM]TFSI ionic liquid are made into a homogeneous transparent solution, after deoxidation treatment, the mixed solution is injected into a mold composed of two pieces of demolding treated substrates and a gasket spaced between the substrates, and ultraviolet light curing is performed, so that a PAT ionic gel layer is prepared, and the thickness of the PAT ionic gel layer is 100-200 μm; S3, the conductive surfaces of the PDMS-AMA composite electrode of S1 are bonded to the upper and lower surfaces of the PAT ionic gel of S2, and the upper and lower electrodes are respectively left with conductive surfaces on the left and right sides for lead wires, and finally the temperature sensor is obtained after packaging.

3. The method of claim 2, wherein the strain-insensitive flexible transparent stretchable temperature sensor is prepared by, In S1, the PDMS elastomer is uniaxially pre-stretched by 40%-60%.

4. The method of claim 2, wherein the strain-insensitive flexible transparent stretchable temperature sensor is prepared by, In S1, the air pressure of the Plasma air plasma treatment is 7-15 Pa, the power is 15-30 W, and the time is 4-7 min.

5. The method of claim 2, wherein the strain-insensitive flexible transparent stretchable temperature sensor is prepared by, In S1, before spin coating, AgNWs are prepared into a solution of 1-3 mg / mL, and MXene is prepared into a solution of 1-2 mg / mL; the rotation speed of each spin coating is 800-1500 rpm, and the time is 50-70 s; and after each spin coating, the sample is dried at 35-50℃ for 1-2 min to remove part of the solvent.

6. The method of claim 2, wherein the strain-insensitive flexible transparent stretchable temperature sensor is prepared by, In S1, the PDMS elastomer is a PDMS film, and the preparation method is as follows: 8-15 wt% PVA solution and PDMS stock solution are prepared, 2 layers of PVA are spin-coated on a glass substrate to form a PVA sacrificial layer; then 1 layer of PDMS film layer is spin-coated, and after the PVA sacrificial layer is dissolved and removed, a PDMS film with a thickness of 10-50 μm is obtained.

7. The method of claim 2, wherein the temperature sensor is a strain-insensitive flexible transparent stretchable temperature sensor. In S1, the MXene is Ti3C2T x MXene, prepared as follows: S11, etching: LiF is dissolved in concentrated hydrochloric acid to form an etching solution, Ti3AlC2 is then added, and the etching reaction solution is obtained after reaction at 30-50℃ for 40-60h; S12, washing: pour the supernatant of the etching reaction solution, take the precipitate and wash it with water by centrifugation for multiple rounds, the rotation speed is gradually increased from 1000 rpm to 3500 rpm, until the pH of the solution after washing is greater than 4, and the mud-like multilayer MXene is obtained after discarding the supernatant; S13, intercalation: disperse the multilayer MXene in water, and perform ultrasonic treatment under the protection of an inert atmosphere to realize the intercalation of water molecules between the MXene layers, and then collect the supernatant by centrifugation to obtain a MXene aqueous solution; S14, freeze-drying: after pre-freezing the MXene aqueous solution, freeze-drying was performed, and a foam-like Ti3C2T x MXene solid was obtained. S14, freeze-drying: after pre-freezing the MXene aqueous solution, freeze-drying was performed, and a foam-like Ti3C2T x MXene solid was obtained.

8. The method of claim 2, wherein the strain-insensitive flexible transparent stretchable temperature sensor is prepared by, In S2, the molar ratio of the acrylamide monomer and the 2,2,2-trifluoroethyl acrylate monomer is 1-2:2-3; the amount of the I2959 photoinitiator is 0.1-1wt% of the total mass of the monomer system, and the amount of the [EMIM]TFSI ionic liquid is 50-70wt% of the total mass of the mixed solution.

9. The method of claim 2, wherein the strain-insensitive flexible transparent stretchable temperature sensor is prepared by, In S2, the power of the ultraviolet light curing is 1-4 mW / cm 2 , and the time is 1-4 h.

10. Use of the strain-insensitive flexible transparent stretchable temperature sensor of claim 1, wherein, Applications include human health monitoring, intelligent prosthesis interaction, or temperature sensing arrays.

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