Flexible self-decoupling three-mode sensor and preparation method thereof

Abstract

The invention provides a flexible self-decoupling three-mode sensor and a preparation method thereof. The sensor comprises a temperature and pressure sensing piece, an upper elastic packaging body, a lower elastic packaging body, an upper flexible electrode and a lower flexible electrode, the temperature and pressure sensing part comprises a conductive sponge and electrodes located on the upper and lower side surfaces of the conductive sponge; the upper elastic packaging body comprises an upper platform and a plurality of upper supporting legs connected to the same side of the upper platform, and the lower elastic packaging body comprises a lower platform and a plurality of upper supporting legs connected to the same side of the lower platform; the temperature and pressure sensing part is located between the upper elastic packaging body and the lower elastic packaging body, the upper side surface and the lower side surface of the conductive sponge are fixedly connected with the upper platform and the lower platform respectively, and meanwhile the upper supporting legs and the lower supporting legs are arranged on the periphery of the conductive sponge in a one-to-one correspondence mode and fixedly connected with each other. The upper flexible electrode and the lower flexible electrode are located on the surfaces of one sides of the upper platform and the lower platform respectively. Based on a special sensing mechanism, the sensing and detection of pressure, approach and temperature are realized under the condition of avoiding signal crosstalk.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible sensors, and particularly to a flexible self-decoupling triple-mode sensor and a preparation method thereof. Background Art

[0002] Flexible sensors are widely used in many aspects such as motion monitoring, human-computer interaction, and health detection, which have received increasing attention. In different application scenarios, flexible sensors need to convert different external stimuli into corresponding signals for output. A single-mode sensor can only detect a single external stimulus, and the application scenarios are limited. Therefore, sensors are developing towards the multi-mode direction, and these sensors can often detect two or more external stimuli. However, multi-mode sensors need to solve the problems of signal interference and decoupling. Because when the external is a single stimulus, the signal crosstalk problem does not need to be considered; when the external stimuli are no longer single, but two or more stimuli, there will be crosstalk between the signals. If the signals output by the two stimuli on the sensor are of the same type, complex decoupling of the composite signal is required to separate the single signal. The decoupling of the sensor composite signal increases the difficulty of signal acquisition, and the decoupling requires certain preconditions and is easily interfered. Here, a self-decoupling multi-mode sensor outputs different types of signals for different external stimuli, with low crosstalk between the signals, and can also collect signals well in the case of non-single stimuli. Therefore, it is still challenging to develop a sensor that can detect pressure, proximity, and temperature with low signal crosstalk. Summary of the Invention

[0003] Based on the technical problems existing in the background art, the present invention proposes a flexible self-decoupling triple-mode sensor and a preparation method thereof. Its special sensing mechanism realizes the perception and detection of pressure, proximity, and temperature while avoiding signal crosstalk.

[0004] A flexible self-decoupling triple-mode sensor proposed by the present invention includes a temperature and pressure sensing element, an upper elastic encapsulation body, a lower elastic encapsulation body, an upper flexible electrode, and a lower flexible electrode;

[0005] The temperature and pressure sensing element includes a conductive sponge and electrodes on the upper and lower surfaces of the conductive sponge;

[0006] The upper elastic encapsulation body includes an upper platform and a plurality of upper legs connected to the same side of the upper platform, and the lower elastic encapsulation body includes a lower platform and a plurality of upper legs connected to the same side of the lower platform;

[0007] The temperature and pressure sensing element is located between the upper elastic encapsulation body and the lower elastic encapsulation body, and the upper and lower surfaces of the conductive sponge with electrodes are respectively fixedly connected to the upper platform and the lower platform. At the same time, the upper legs and the lower legs are arranged in one-to-one correspondence on the outer periphery of the conductive sponge and are fixedly connected to each other;

[0008] The upper flexible electrode and the lower flexible electrode are respectively located on the side surfaces of the upper platform and the lower platform without legs.

[0009] In the present invention, the conductive sponge can generate piezoresistive signals under pressure, realizing the detection of pressure. At the same time, it has a thermoelectric effect and can generate thermoelectric voltage under the stimulation of external temperature changes, realizing the detection of temperature. The upper and lower elastic encapsulation bodies are cooperatively installed on the outer periphery of the conductive sponge, and they have the same movement trend as the conductive sponge, and will have a pressure capacitance signal that changes synchronously with the piezoresistive signal of the conductive sponge. Then, the electrodes jointly act to form an edge electric field. Based on the edge field effect, it has a proximity sensing function and realizes the detection of proximity.

[0010] Based on the above sensing mechanism, in the present invention, the external pressure is encoded as the synchronous change signals of piezoresistance and pressure capacitance of the sensor, the proximity is encoded as the capacitance change signal of the sensor, and the temperature is encoded as the voltage signal of the sensor, which can avoid crosstalk between signals. Through this measure, a self-decoupling sensor capable of simultaneously realizing pressure, proximity and temperature sensing is prepared, which can meet the diverse actual application requirements.

[0011] Preferably, the conductive sponge is a porous sponge filled with conductive fillers;

[0012] Preferably, the conductive fillers include polyaniline, PEDOT:PSS, graphene, multi-walled carbon nanotubes and silicone rubber;

[0013] Preferably, the mass ratio of polyaniline, PEDOT:PSS, graphene, multi-walled carbon nanotubes and silicone rubber is 1:0.8 - 1.2:2 - 4:0.8 - 1.2:8 - 10.

[0014] In the present invention, the filling of polyaniline, PEDOT:PSS, graphene, multi-walled carbon nanotubes and silicone rubber on the sponge constructs a conductive sponge with a sensitive piezoresistive and thermoelectric network.

[0015] Preferably, in the upper elastic encapsulation body, the upper legs are symmetrically arranged relative to the center of the upper platform, and the upper legs form an angle of 45° with the plane where the upper platform is located; in the lower elastic encapsulation body, the lower legs are symmetrically arranged relative to the center of the lower platform, and the lower legs also form an angle of 45° with the plane where the lower platform is located.

[0016] In the present invention, the upper and lower elastic encapsulation bodies with a 45° bending symmetric structure can construct a perfect pressure capacitance network, so that it has a pressure capacitance signal that changes more synchronously with the piezoresistive signal of the sponge.

[0017] Preferably, in the upper elastic encapsulation body, a groove for fitting and assembling with the conductive sponge is provided on one side surface of the upper platform where the upper leg is located; in the lower elastic encapsulation body, a groove for fitting and assembling with the conductive sponge is also provided on one side surface of the lower platform where the lower leg is located.

[0018] In the present invention, by providing the groove, the conductive sponge can be more firmly fitted and installed with the upper elastic encapsulation body and the lower elastic encapsulation body, and the hindrance effect of the upper elastic encapsulation body and the lower elastic encapsulation body on the heat conduction of the conductive sponge can be reduced.

[0019] Preferably, the upper flexible electrode and the lower flexible electrode are conductive adhesive tapes, and the upper elastic encapsulation body and the lower elastic encapsulation body are silicone rubber elastic encapsulation bodies.

[0020] The present invention also provides a preparation method of a flexible self-decoupling three-mode sensor, comprising the following steps:

[0021] S1. Immerse the porous sponge in a conductive filler solution comprising polyaniline, PEDOT:PSS, graphene, multi-walled carbon nanotubes, and silicone rubber. After taking it out and drying, repeat the immersion several times to obtain a conductive sponge; Adhere copper foils as electrodes to the upper and lower side surfaces of the conductive sponge respectively to obtain a temperature and pressure sensing element.

[0022] S2. Add the silicone rubber solution into a mold with a preset inner cavity shape to solidify, and after peeling, obtain the upper elastic encapsulation body and the lower elastic encapsulation body; The upper elastic encapsulation body comprises an upper platform and a plurality of upper legs connected to the same side of the upper platform, and the lower elastic encapsulation body comprises a lower platform and a plurality of lower legs connected to the same side of the lower platform.

[0023] S3. Adhere the conductive adhesive tapes as the upper flexible electrode and the lower flexible electrode to the side surfaces of the upper platform and the lower platform without legs respectively; Fix the upper platform to the upper side surface of the conductive sponge, fix the lower platform to the lower surface of the conductive sponge, and arrange the upper legs and the lower legs in one-to-one correspondence on the outer periphery of the conductive sponge and fix them to each other, thus obtaining the flexible self-decoupling three-mode sensor.

[0024] Preferably, in step S1, polyaniline, PEDOT:PSS, graphene, multi-walled carbon nanotubes, and silicone rubber are added to naphtha and dispersed evenly to obtain a conductive filler solution.

[0025] Preferably, the mass ratio of the polyaniline, PEDOT:PSS, graphene, multi-walled carbon nanotubes, and silicone rubber is 1:0.8 - 1.2:2 - 4:0.8 - 1.2:8 - 10.

[0026] Preferably, the impregnation rate is 200 - 500 rpm, and the impregnation time is 5 - 20 min; The drying temperature is 40 - 60 °C, and the time is 0.5 - 2 h.

[0027] Preferably, in step S2, a mold with a preset inner cavity shape is printed by a 3D printer.

[0028] Preferably, in the upper elastic encapsulation body, the upper legs are symmetrically arranged relative to the center of the upper platform, and the upper legs form an angle of 45° with the plane where the upper platform is located; in the lower elastic encapsulation body, the lower legs are symmetrically arranged relative to the center of the lower platform, and the lower legs also form an angle of 45° with the plane where the lower platform is located.

[0029] Preferably, the solidification time is 6 - 12 h.

[0030] Preferably, in step S1, a copper foil is adhered to the upper and lower surfaces of the conductive sponge using a silver paste solution; in step S2, the upper platform is fixedly connected to the upper surface of the conductive sponge using a silver paste solution, and the lower platform is fixedly connected to the lower surface of the conductive sponge using a silver paste solution.

[0031] Preferably, in step S3, the upper legs and the lower legs are fixedly connected to each other using a silicone rubber binder.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) For the sensor of the present invention, pressure can be encoded into synchronous piezoresistive and piezocapacitive signals, proximity can be encoded into capacitive signals, and temperature can be encoded into voltage signals. Therefore, regardless of whether the external stimulus is a single stimulus or a composite stimulus, the sensor can directly output corresponding signals to reflect the external stimulus, achieving self - decoupling of the sensor output signals and low crosstalk between signals.

[0034] (2) By selecting different conductive fillers and their ratios, the piezoresistive and thermoelectric voltage performance of the sensor of the present invention is more significant; by selecting upper and lower elastic encapsulation bodies with 45° bending symmetry, in addition to generating piezocapacitive signals, the sensor also has the performance of proximity sensing; the sensor with a special structure of the present invention exhibits significant advantages such as high sensitivity, excellent repeatability, and fast response time.

[0035] (3) Compared with a single - mode sensor, the multimode sensor of the present invention can sense pressure, proximity, and temperature, with a wider application range; it realizes the sensing of multiple external stimuli by a single device, with more significant application advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the overall structure of the sensor according to Embodiment 1 of the present invention;

[0037] Figure 2Schematic diagram of the manufacturing process of the sensor described in Example 1 of the present invention: (a) is a schematic diagram of the manufacturing process of the conductive sponge; (b) is a schematic diagram of the manufacturing process of the upper elastic encapsulation body and the lower elastic encapsulation body; (c) is a schematic diagram of the assembly process of the conductive sponge, the upper elastic encapsulation body, and the lower elastic encapsulation body;

[0038] Figure 3 Surface SEM images of the porous sponge in Example 1 of the present invention before and after impregnation with a conductive filler solution: (a) is an SEM image of the porous sponge skeleton before impregnation with the conductive filler solution; (b) is an SEM image of the porous sponge skeleton after impregnation with the conductive filler solution; (c) and (d) are locally enlarged SEM images of the porous sponge skeleton after impregnation with the conductive filler solution; (e) is an element distribution diagram of the surface material of the porous sponge after impregnation with the conductive filler solution;

[0039] Figure 4 Figures 1 and 2 show optical images of the sensor before and after a force is applied, and a diagram illustrating the sensor's pressure signal generation mechanism. (a) shows optical images of the sensor before and after a force is applied; (b) shows an equivalent circuit diagram of the sensor's conductive sponge in its original and compressed states; and (c) shows a schematic diagram of the local structure of the sensor's conductive sponge in its original and compressed states.

[0040] Figure 5 This is the sensitivity curve of the sensor described in Example 1 of the present invention when subjected to a certain pressure;

[0041] Figure 6 The response and recovery time of the piezoresistive and piezoresistive signals of the sensor according to Example 1 of the present invention at different pressures;

[0042] Figure 7 The curves showing the change of the piezoresistance and piezocaputical signals of the sensor described in Example 1 of the present invention during long-term cycling are shown below:

[0043] Figure 8 This is a diagram of the proximity sensing mechanism of the sensor described in Example 1 of the present invention;

[0044] Figure 9 This is a diagram of the proximity sensing performance of the sensor described in Example 1 of the present invention;

[0045] Figure 10 Diagrams of the thermoelectric sensing mechanism of the sensor described in Example 1 of the present invention: (a) Temperature distribution of the simulation model of the sensor at ΔT = 100K; (b) Potential distribution of the simulation model of the sensor at ΔT = 100K, ΔP = 0kPa; (c) Potential distribution of the simulation model of the sensor at ΔT = 100K, ΔP = 10kPa;

[0046] Figure 11 This is the thermoelectric sensitivity curve of the sensor described in Example 1 of the present invention;

[0047] Figure 12 Thermoelectric characteristic diagram of the sensor described in Embodiment 1 of the present invention under different applied pressures;

[0048] Figure 13 Electric signal diagram generated by the heating-cooling cycle of the sensor described in Embodiment 1 of the present invention under different temperature differences;

[0049] Figure 14 Resistance and capacitance curves of the sensor described in Embodiment 1 of the present invention varying with temperature;

[0050] Figure 15 Comparison diagram of piezoresistive and thermoelectric properties of the porous sponge of the present invention after impregnation with different conductive fillers;

[0051] Figure 16 Comparison diagram of piezoresistive and thermoelectric properties of the porous sponge of the present invention after impregnation with different ratios of conductive fillers;

[0052] Figure 17 Comparison diagram of the piezocapacitive performance of the sensor corresponding to the elastic encapsulation body of the present invention at different angles: (a) Piezocapacitive signals of the sensor at different angles (θ = 180°, 90°, 45°, 30°); (b) Piezocapacitive signals of the sensor at different angles (θ = 50°, 45°, 40°); (c) Comparison diagram of the cyclic stability of piezocapacitive signals at different angles. Detailed implementation manners

[0053] Next, the technical solutions of the present invention will be described in detail through specific embodiments. It should be clearly stated that these embodiments are used for illustration purposes only and are not construed as limiting the scope of the present invention.

[0054] Embodiment 1

[0055] Referring to Figure 1 , this embodiment proposes a flexible self-decoupled triple-mode sensor, including a temperature and pressure sensing element, an upper elastic encapsulation body, a lower elastic encapsulation body, an upper flexible electrode, and a lower flexible electrode;

[0056] The upper elastic encapsulation body includes an upper platform and four upper legs connected to the same side of the upper platform. The lower elastic encapsulation body includes a lower platform and four lower legs connected to one side of the lower platform. In a preferred embodiment, the upper platform and the lower platform are square. The upper legs and the lower legs are respectively located in the four corner regions of the upper platform and the lower platform, and are symmetrically arranged with respect to the centers of the upper platform and the lower platform. At the same time, the upper legs form an angle of 45° with the plane where the upper platform is located, and the lower legs form an angle of 45° with the plane where the lower platform is located. In a preferred embodiment, the upper elastic encapsulation body and the lower elastic encapsulation body are silicone rubber elastic encapsulation bodies;

[0057] The temperature and pressure sensing element includes a conductive sponge and electrodes located on the upper and lower surfaces of the conductive sponge; in a preferred embodiment, the electrodes are copper foils, which are fixedly connected to the upper and lower surfaces of the conductive sponge through a silver glue solution;

[0058] The upper and lower surfaces of the conductive sponge fixedly connected with the electrodes are also respectively fixedly connected between the upper platform and the lower platform, and the upper legs and the lower legs are arranged in one-to-one correspondence on the outer periphery of the conductive sponge and fixedly connected to each other; in a preferred embodiment, the conductive sponge is cube-shaped, and square grooves for fitting and installing with the upper and lower surfaces of the conductive sponge are respectively formed on one surface of the upper platform with upper legs and one surface of the lower platform with lower legs. The upper and lower surfaces of the conductive sponge fixedly connected with the electrodes are placed in the square grooves for fixed installation, and the contact parts are connected with a silver glue solution; in a preferred embodiment, the conductive sponge is a sponge filled with conductive fillers, and the conductive fillers include polyaniline, PEDOT:PSS, graphene, multi-walled carbon nanotubes and silicone rubber with a mass ratio of 1:0.8 - 1.2:2 - 4:0.8 - 1.2:8 - 10;

[0059] The upper flexible electrode and the lower flexible electrode are respectively located on one surface of the upper platform and the lower platform without legs; in a preferred embodiment, the upper flexible electrode and the lower flexible electrode are conductive tapes, which are directly adhered to one surface of the upper platform or the lower platform without legs; in a preferred embodiment, the middle part of the conductive tape has a through hole corresponding to the area of the projection of the conductive sponge on the upper platform or the lower platform, so as to weaken the hindrance effect of the conductive tape on the heat conduction of the conductive sponge;

[0060] In a preferred embodiment, the upper elastic encapsulation body and the lower elastic encapsulation body also respectively include an upper silicone film and a lower silicone film, which are also located on one surface of the upper platform or the lower platform without legs and completely cover the upper flexible electrode and the lower flexible electrode, so as to protect the upper flexible electrode and the lower flexible electrode.

[0061] In the above flexible self-decoupling three-mode sensor, the internal conductive sponge is a pressure (piezoresistive) and temperature sensitive layer, and the external elastic encapsulation body is a pressure (piezoelectric capacitive) and proximity sensitive layer; when the sensor is compressed or restored, the conductive sponge and the elastic encapsulation body are regarded as a whole and have a consistent movement process, and the piezoresistive and piezoelectric capacitive signals output have the same change trend; when an external object approaches the sensor, the edge field of the sensor changes, and a changing capacitance signal is output; when the external temperature changes, the existence of the temperature difference at both ends of the sensor will cause the generation of a voltage signal.

[0062] Referring to Figure 2 , this embodiment also proposes a preparation method of a flexible self-decoupling three-mode sensor, which specifically includes:

[0063] (1) Polyaniline (PANI, purity > 98%, particle size < 30 μm, Coolchemical science and technology (Beijing) co., Ltd), PEDOT:PSS (P:P, 1.3 - 1.7 wt% dispersion in H2O, Coolchemical science and technology (Beijing) co., Ltd), graphene (GR, number of layers 1 - 3, purity > 98%, sheet diameter 7 - 13 μm, Shenzhen Hongdachang Evolution Technology Co., Ltd), multi-walled carbon nanotubes (MWCNTs, purity > 99.5%, tube diameter 10 - 20 μm, tube length < 50 μm, Guangdong Innovative Materials (Shenzhen) Co., Ltd) and silicone rubber (SR, GR GD401, Zhonghao Chenguang Chemical Research Institute Co., Ltd) were added to 40 mL of naphtha according to a mass ratio of 1:1:3:1:10, heated to 50 °C and magnetically stirred for 60 min to obtain a uniformly dispersed conductive filler solution; a clean porous sponge with dimensions of 10 × 10 × 10 mm was impregnated into the conductive filler solution, magnetically stirred at a speed of 300 rpm for 10 min, the porous sponge was taken out, and the excess solution was gently pressed out with tweezers, and dried in a constant temperature drying oven at 55 °C for 1 h. The above impregnation process was repeated four times to obtain a conductive sponge; a silver paste solution (YC-02, Nanjing Xilite Adhesive Co., Ltd) was evenly coated on a copper foil with dimensions of 10 × 10 mm (thickness 0.1 mm, Shenzhen Meicheng Adhesive Products Co., Ltd) and pasted on the upper and lower surfaces of the conductive sponge.

[0064] (2) Use a 3D printer to print a mold with a preset inner cavity shape. Drop liquid silicone rubber (GR GD401, Zhonghao Chenguang Chemical Research Institute Co., Ltd.) into the mold. After fully solidifying for 12 h, peel it off to obtain an upper elastic encapsulation body and a lower elastic encapsulation body. The structures of the upper elastic encapsulation body and the lower elastic encapsulation body are the same. The upper elastic encapsulation body includes an upper platform with dimensions of 25 mm × 25 mm × 1 mm in length, width, and height, and four upper legs (cylindrical, with a diameter of 2 mm and a length of 8 mm) connected to the same side of the upper platform. The upper legs are symmetrically arranged relative to the center of the upper platform, and the upper legs form a 45° angle with the plane where the upper platform is located. At the same time, on the surface of the upper platform with the upper legs, there is a groove with dimensions of 10 × 10 × 0.5 mm in length, width, and depth for fitting and assembling with a conductive sponge; the lower elastic encapsulation body includes a lower platform and four lower legs connected to the same side of the lower platform. The lower legs are also symmetrically arranged relative to the center of the lower platform, and the lower legs also form a 45° angle with the plane where the lower platform is located. At the same time, on the surface of the lower platform with the lower legs, there is a groove with dimensions of 10 × 10 × 0.5 mm in length, width, and depth for fitting and assembling with a conductive sponge; Trim the conductive tape (with a thickness of 0.1 mm, Shenzhen Meicheng Adhesive Products Co., Ltd.) into a square, with a through-hole in the middle with dimensions of 10 × 10 mm in length and width. Then paste the conductive tape on the surfaces of the upper platform and the lower platform without legs.

[0065] (3) Assemble the upper elastic encapsulation body, the conductive sponge, and the lower elastic encapsulation body from top to bottom. Specifically, fit and install the groove on the upper platform of the upper elastic encapsulation body with the upper side surface of the copper foil bonded to the conductive sponge, and bond them with conductive silver glue on their contact surfaces. Fit and install the groove on the lower platform of the lower elastic encapsulation body with the lower side surface of the copper foil bonded to the conductive sponge, and bond them with conductive silver glue on their contact surfaces; At the same time, the upper legs of the upper elastic encapsulation body and the lower legs of the lower elastic encapsulation body are arranged in one-to-one correspondence on the outer periphery of the conductive sponge and are fixedly bonded to each other with silicone rubber adhesive (GuPai799, Dongguan Gupai New Material Technology Co., Ltd.). The obtained whole is placed in a vacuum furnace and dried for 10 h to ensure full curing, thus obtaining the flexible self-decoupling three-mode sensor.

[0066] Figure 2 It is a schematic diagram of the preparation process of the sensor described in Embodiment 1 of the present invention. Figure 2 a shows a schematic diagram of the preparation process of the conductive sponge in the sensor. Figure 2 b shows a schematic diagram of the preparation process of the upper elastic encapsulation body and the lower elastic encapsulation body in the sensor. Figure 2 c shows a schematic diagram of the assembly process of the conductive sponge, the upper elastic encapsulation body, and the lower elastic encapsulation body in the sensor.

[0067] Figure 3 It is the surface SEM image of the porous sponge before and after impregnating with the conductive filler solution in Embodiment 1 of the present invention. Figure 3a and 3b are the SEM images of the porous sponge skeleton before and after impregnation with the conductive filler solution. As can be seen from Figure 3 a and 3b, after impregnation, the conductive filler is successfully attached to the surface of the porous sponge. Especially at the joints of the porous sponge skeleton, due to its larger surface area, more conductive filler is attached; Figure 3 c and 3d are the partial enlarged SEM images of the porous sponge skeleton after impregnation with the conductive filler solution. As can be seen from Figure 3 c, the conductive filler is evenly attached to the surface of the porous sponge skeleton; as can be seen from Figure 3 d, the conductive materials used in impregnation, graphene, multi-walled carbon nanotubes, and polyaniline (PEDOT:PSS is a liquid and is attached to the surface and not marked), there are strong π-π coordination and hydrogen bonds between graphene and polyaniline, which can make the mixture more evenly distributed, and the tubular structure of multi-walled carbon nanotubes can make the combination between the mixtures more tightly and firmly; Figure 3 e is the elemental distribution map of the surface material of the porous sponge after impregnation with the conductive filler solution, specifically the distribution maps of elements carbon (C), nitrogen (N), sulfur (S), silicon (Si), and oxygen (O). As can be seen from Figure 3 e, the uniform distribution of elements reflects the uniform distribution of the conductive material on the surface of the porous sponge, indicating that the impregnated porous sponge has achieved the expected purpose.

[0068] Figure 4 This is the optical image of the sensor before and after being stressed and the mechanism diagram of the sensor pressure signal generation in Example 1 of the present invention. Figure 4 a is the optical image of the sensor before and after being stressed. As can be seen from Figure 4 a, after impregnation treatment, the composite conductive material is attached to the porous sponge skeleton, so that the porous sponge skeleton has conductivity to form a conductive path; when the internal sponge is stressed and squeezed, after the pressure is released, the elasticity of the sponge and the external elastic encapsulation structure itself act together to make the sponge return to its original state; Figure 4 b is the equivalent circuit diagram of the conductive sponge of the sensor in the original and compressed states. As can be seen from Figure 4 b, in the original state, the conductive sponge skeleton is not deformed, the formed conductive path is limited, the air resistance is very large, and the initial resistance of the sponge is relatively large; while in the compressed state, the contact between the conductive sponge skeletons increases; Figure 4 c is the local structure schematic diagram of the conductive sponge of the sensor in the original and compressed states. As can be seen from Figure 4 c, the voids between the sponge skeletons decrease, the conductive path increases, the sponge resistance decreases, and the change in the sponge resistance can reflect the external applied pressure; in addition, the distance between the upper and lower electrodes of the sensor changes, and according to the parallel plate capacitor principle, the capacitance of the electrodes on the elastic encapsulation structure of the sensor will also change; the change in capacitance can also reflect the pressure situation.

[0069] Figure 5 This is the sensitivity curve of the sensor described in Embodiment 1 of the present invention when it is subjected to a certain pressure (0 - 160 kPa). It can be seen from Figure 5 that the sensitivity S of the piezoresistive signal is S = (ΔR / R0)×100% / ΔP, where ΔR = R P - R0; in the low - pressure range (0 - 10 kPa), the sensitivity of the piezoresistive signal of the sensor is - 12.5 kPa -1 , and in the high - pressure range (10 - 160 kPa), the sensitivity of the piezoresistive signal of the sensor is - 0.0053 kPa -1 ; the sensitivity S of the piezocapacitive signal is S = (ΔC / C0) / P. In the low - pressure (0 - 10 kPa), medium - pressure (10 - 70 kPa), and high - pressure (70 - 160 kPa) ranges, the sensitivities of the piezocapacitive signal of the sensor are 0.302 kPa -1 , 0.058 kPa -1 , and 0.017 kPa -1 , respectively. The results show that the sensor has good sensitivity in the small - pressure range.

[0070] Figure 6 This is the response and recovery times of the piezoresistive and piezocapacitive signals of the sensor described in Embodiment 1 of the present invention under different pressures. It can be seen from Figure 6 that the response - recovery times of the piezoresistive and piezocapacitive signals show a decreasing trend as the applied pressure decreases; the sensor responds quickly to pressure changes, which is the result of the combined action of the elastic forces of the sponge and silicone rubber.

[0071] Figure 7 This is the change curves of the piezoresistive and piezocapacitive signals of the sensor described in Embodiment 1 of the present invention during long - term cycling. It can be seen from Figure 7 that the waveform changes of the piezoresistive and piezocapacitive signals are stable during 1000 cycles, showing excellent repeatability.

[0072] Figure 8 This is the proximity sensing mechanism diagram of the sensor described in Embodiment 1 of the present invention. It can be seen from Figure 8 that the electrodes of the sensor excite an electric field. When an external object approaches, according to the edge - field effect, the electric potential on the sensor plate is changed, and the capacitance of the sensor electrode decreases, realizing the proximity sensing of the external object; the electrodes of the sensor include the electrodes of the elastic encapsulation and the two - side electrodes of the conductive sponge. The two parts of the electrodes work together to form an electric field around the sensor; during the actual test, the two - side electrodes of the conductive sponge are grounded, and the capacitance change of the elastic - encapsulation electrode is measured.

[0073] Figure 9 This is the proximity sensing performance diagram of the sensor described in Embodiment 1 of the present invention. It can be seen from Figure 9It can be seen that a copper sheet measuring 10mm x 10mm x 1mm in length, width and height is used as an external object for proximity sensing to test the proximity performance of the sensor. The proximity performance is quantified by the change in sensor capacitance, ΔC = C-C0 (initial capacitance C0: the capacitance when the external object is in close contact with the sensor surface). When the copper sheet approaches from 200mm directly above the sensor, the capacitance of the electrodes on the sensor's silicone rubber structure decreases. When the copper sheet approaches within the close range (0-100mm), the sensor's capacitance changes more dramatically than at the far range (100-200mm). This is mainly because the sensor's fringe electric field weakens with increasing spatial distance, and the object's influence on the sensor's electric field weakens, resulting in no significant change in capacitance.

[0074] Figure 10 This is a diagram of the thermoelectric sensing mechanism of the sensor described in Example 1 of the present invention. Figure 10 It can be seen that the sensor's perception of temperature changes is based on the thermoelectric effect of the sponge inside the sensor. The impregnation process makes the thermoelectric material adhere to the sponge skeleton. When there is a temperature difference between the upper and lower plates of the sensor, an electrical signal will be generated. The temperature change is fed back by measuring the voltage signal at both ends of the sponge. A 3D model of the sensor is established in COMSOL Multiphysics, and one of the cross sections is selected as the observation object. Figure 10 From a, we can see that the temperature of the upper end of the sensor is maintained at 390K, and the temperature of the lower end is maintained at 290K. The temperature is distributed in a gradient on the sensor. The temperature difference of the sensor is ΔT = 100K. The thermoelectric effect generates a voltage signal. Figure 10 From b, we can see that when ΔT = 100K and ΔP = 0kPa, the potential distribution of the sensor is 0.6mV. There is no thermoelectric effect in the external SR structure, and the potential is always 0mV. Figure 10 c It can be seen that the potential distribution range of the sensor becomes narrower when ΔT = 100K and ΔP = 10kPa, but the voltage difference across the sensor sponge is still 0.6mV. The existence of pressure has no effect on the thermoelectric effect of the sensor.

[0075] Figure 11 is the thermoelectric sensitivity curve of the sensor described in Example 1 of the present invention. Figure 11 It can be seen that the temperature sensitivity of the sensor is represented by the slope of the generated thermoelectric voltage. When ΔT is in the range of 0 to 100K (30-130℃), the temperature sensitivity of the sensor S is T It is 6.006μV / K and has good linear characteristics.

[0076] Figure 12 The thermoelectric characteristic diagram of the sensor described in Example 1 of the present invention under different pressures. Figure 12 It can be seen that under the same temperature difference and different pressure, the electrical signals generated by the sensor are almost the same, indicating that the pressure change has no effect on the thermoelectric performance of the sensor, which is consistent with the Figure 10Correspond to each other.

[0077] Figure 13 This is the electrical signal diagram generated by the sensor described in Embodiment 1 of the present invention during the heating-cooling cycle at different temperature differences (10K, 15K, 20K, 25K, 30K). It can be seen from Figure 13 that the amplitude of the voltage waveform at the same temperature difference is consistent, and the voltage waveforms at different temperature differences are clearly distinguishable. The sensor has excellent stability and temperature discrimination ability.

[0078] Figure 14 This is the resistance and capacitance curves of the sensor described in Embodiment 1 of the present invention with temperature change. It can be seen from Figure 14 that the temperature change has an impact on both the initial resistance and initial capacitance of the sensor; regarding the impact of the external temperature change on the piezoresistive signal of the sensor, the sensor is heated from 30°C to 130°C. The sponge resistance fluctuates continuously under the influence of temperature but with a small amplitude, and the maximum fluctuation ΔR / R0(100%) = -5; the change amplitude of the sensor's capacitance is smaller than that of the sponge resistance, and the maximum change ΔC / C0 = -0.014; combined with the temperature-insensitive characteristic of the piezoresistive signal, it can be known that the impact of the ambient temperature change on the pressure signal of the sensor is limited and can be ignored; under the conditions of external pressure, proximity, and temperature change, there is low crosstalk between the signals generated by the sensor, achieving self-decoupling of the sensor output signal.

[0079] Figure 15 This is the comparison diagram of piezoresistive and thermoelectric properties of the porous sponge of the present invention impregnated with different conductive fillers. It can be seen from Figure 15 that the piezoresistive and thermoelectric properties of sensors with different raw material compositions are different. The sensitivity of the sensor containing only GR / MWCNTs is relatively low, while the sensitivities of the sensors containing GR / MWCNTs / PANI and GR / MWCNTs / PANI / PEDOT:PSS are relatively high and similar; however, in terms of thermoelectric properties, the sensor containing GR / MWCNTs / PANI / PEDOT:PSS has better thermoelectric properties, indicating that the addition of PEDOT:PSS can improve the thermoelectric properties.

[0080] Figure 16 This is the comparison diagram of piezoresistive and thermoelectric properties of the porous sponge of the present invention impregnated with different ratios of conductive fillers. It can be seen from Figure 16 that the piezoresistive and thermoelectric properties of sensors with different material ratios are different: when the ratio of GR and MWCNTs is fixed at 1:1, and on this basis, the content of PANI is changed, and the impact of the relative content change of PEDOT:PSS / PANI on the piezoresistivity and thermoelectricity of the sensor is discussed. It is found that when the material content ratio of the conductive filler solution containing GR / MWCNTs / PANI / PEDOT:PSS is 1:1:3:1, the thermoelectric properties of the sensor are the best.

[0081] Figure 17 This is a comparison chart of the piezoresistive performance of the sensors corresponding to the elastic encapsulation bodies of the present invention at different angles. As can be seen from Figure 17 it, different angles (θ, where θ is the included angle between the upper and lower legs) of the bending symmetric structure will affect the sensitivity and stability of the sensor; within the low-pressure range (0 - 50 kPa), the sensitivity of the sensor increases as the angle becomes smaller, but a smaller angle will narrow the pressure detection range of the sensor, and at the same time, a decrease in the angle will increase the instability of the sensor; therefore, considering the sensitivity, measurement range, and stability comprehensively, an angle θ of 90° is selected, that is, the sensor with upper and lower elastic encapsulation bodies bent symmetrically at 45°.

[0082] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution of the present invention and its inventive concept, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A flexible self-decoupling triple-mode sensor, characterized in that, It includes a temperature and pressure sensing element, an upper elastic encapsulation body, a lower elastic encapsulation body, an upper flexible electrode and a lower flexible electrode; The temperature and pressure sensing element includes a conductive sponge and electrodes located on the upper and lower surfaces of the conductive sponge; The upper elastic encapsulation body includes an upper platform and a plurality of upper legs connected to the same side of the upper platform, and the lower elastic encapsulation body includes a lower platform and a plurality of upper legs connected to the same side of the lower platform; The temperature and pressure sensing element is located between the upper elastic encapsulation body and the lower elastic encapsulation body, and the upper and lower surfaces of the conductive sponge with electrodes are respectively fixedly connected to the upper platform and the lower platform. At the same time, the upper legs and the lower legs are arranged in one-to-one correspondence on the outer periphery of the conductive sponge and are fixedly connected to each other; The upper flexible electrode and the lower flexible electrode are respectively located on the surface of the upper platform and the lower platform without legs.

2. The flexible self-decoupling triple-mode sensor according to claim 1, wherein The conductive sponge is a porous sponge filled with conductive filler; Preferably, the conductive filler includes polyaniline, PEDOT:PSS, graphene, multi-walled carbon nanotubes and silicone rubber; Preferably, the mass ratio of polyaniline, PEDOT:PSS, graphene, multi-walled carbon nanotubes and silicone rubber is 1:0.8 - 1.2:2 - 4:0.8 - 1.2:8 - 10.

3. The flexible self-decoupling triple-mode sensor according to claim 1 or 2, characterized in that, In the upper elastic encapsulation body, the upper legs are symmetrically arranged relative to the center of the upper platform, and the upper legs form an angle of 45° with the plane where the upper platform is located; in the lower elastic encapsulation body, the lower legs are also symmetrically arranged relative to the center of the lower platform, and the lower legs also form an angle of 45° with the plane where the lower platform is located.

4. The flexible self-decoupling triple-mode sensor according to any one of claims 1-3, characterized in that, In the upper elastic encapsulation body, a groove for fitting with the conductive sponge is formed on the surface of the upper platform with upper legs; in the lower elastic encapsulation body, a groove for fitting with the conductive sponge is also formed on the surface of the lower platform with lower legs.

5. The flexible self-decoupling triple-mode sensor according to any one of claims 1-4, characterized in that, The upper flexible electrode and the lower flexible electrode are conductive adhesive tapes, and the upper elastic encapsulation body and the lower elastic encapsulation body are silicone rubber elastic encapsulation bodies.

6. A preparation method of a flexible self-decoupling triple-mode sensor, characterized in that, It includes the following steps: S1. Immerse the porous sponge in a conductive filler solution including polyaniline, PEDOT:PSS, graphene, multi-walled carbon nanotubes and silicone rubber. After taking it out and drying, immerse it several times repeatedly to obtain a conductive sponge; use copper foil as electrodes and adhere them to the upper and lower surfaces of the conductive sponge respectively to obtain a temperature and pressure sensing element; S2. Add silicone rubber solution into a mold with a preset inner cavity shape and let it solidify. After peeling, obtain the upper elastic encapsulation body and the lower elastic encapsulation body; the upper elastic encapsulation body includes an upper platform and a plurality of upper legs connected to the same side of the upper platform, and the lower elastic encapsulation body includes a lower platform and a plurality of lower legs connected to the same side of the lower platform; S3. Use conductive adhesive tapes as the upper flexible electrode and the lower flexible electrode and adhere them to the surfaces of the upper platform and the lower platform without legs respectively; fixedly connect the upper platform to the upper surface of the conductive sponge, fixedly connect the lower platform to the lower surface of the conductive sponge, and the upper legs and the lower legs are arranged in one-to-one correspondence on the outer periphery of the conductive sponge and are fixedly connected to each other, thus obtaining the flexible self-decoupling three-mode sensor.

7. The preparation method of the flexible self-decoupling triple-mode sensor according to claim 6, characterized in that, In step S1, polyaniline, PEDOT:PSS, graphene, multi-walled carbon nanotubes and silicone rubber are added to naphtha and dispersed evenly to obtain a conductive filler solution; Preferably, the mass ratio of the polyaniline, PEDOT:PSS, graphene, multi-walled carbon nanotubes and silicone rubber is 1:0.8-1.2:2-4:0.8-1.2:8-10; Preferably, the impregnation rate is 200-500 rpm, and the impregnation time is 5-20 min; the drying temperature is 40-60 °C, and the time is 0.5-2 h.

8. The preparation method of the flexible self-decoupling triple-mode sensor according to claim 6 or 7, characterized in that, In step S2, a mold with a preset inner cavity shape is printed by a 3D printer; Preferably, in the upper elastic encapsulation body, the upper legs are symmetrically arranged relative to the center of the upper platform, and the upper legs form a 45° angle with the plane where the upper platform is located; in the lower elastic encapsulation body, the lower legs are symmetrically arranged relative to the center of the lower platform, and the lower legs also form a 45° angle with the plane where the lower platform is located; Preferably, the setting time is 6-12 h.

9. The preparation method of the flexible self-decoupling triple-mode sensor according to any one of claims 6-8, characterized in that, In step S1, the copper foil is adhered to the upper and lower surfaces of the conductive sponge by a silver paste solution; in step S2, the upper platform is fixedly connected to the upper surface of the conductive sponge by a silver paste solution, and the lower platform is fixedly connected to the lower surface of the conductive sponge by a silver paste solution.

10. The preparation method of the flexible self-decoupling triple-mode sensor according to any one of claims 6-9, characterized in that, In step S3, the upper legs and the lower legs are fixedly connected to each other by a silicone rubber binder.

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