A piezoresistive silicone rubber flexible sensor and its preparation method

Abstract

The present invention provides a piezoresistive silicone rubber flexible sensor and a preparation method thereof, which belongs to the field of sensor technology. The present invention first uses an emulsion ice template method to prepare an AgNW / cPDMS three-dimensional porous material, and then uses the material as a matrix to prepare a Ppy / AgNW / cPDMS three-dimensional porous material, and then prepares the Ppy / AgNW / cPDMS three-dimensional porous material into a Ppy / AgNW / cPDMS flexible sensor. The Ppy / AgNW / cPDMS three-dimensional porous material prepared by the method of the present invention effectively avoids template residue and solves the influence of template residue on the mechanical properties of the material. In addition, thanks to the hydrophilic and thickening properties of sodium carboxymethyl cellulose (CMC), the problems of poor orientation and hydrophilicity of the prepared three-dimensional porous material are effectively solved. Moreover, the emulsion ice template method used in the present invention is simple, low-cost and environmentally friendly.

Description

Technical Field

[0001] The present invention belongs to the technical field of sensors, and in particular relates to a piezoresistive silicone rubber flexible sensor and a preparation method thereof. Background Art

[0002] Piezoresistive sensors are important subcomponents of various electronic devices, converting deformation caused by external mechanical stimuli into electrical signals. Compared to the brittle sensors currently commercially available, flexible, wearable polymer-based piezoresistive sensors have garnered widespread attention in the sensor field and have become a research hotspot in this area.

[0003] Flexible piezoresistive sensors are usually composed of a flexible polymer matrix and a conductive active layer. Their working principle is that under the action of pressure, the sensor deforms, and the contact between the conductive active layers causes the conductive path to change, causing the electrical signal transmitted by the sensor to change.

[0004] On the one hand, polydimethylsiloxane (PDMS) has become a common polymer matrix for flexible sensors due to its advantages such as low modulus, good flexibility, low relaxivity, and good biocompatibility. On the other hand, polypyrrole (PPy), an intrinsically conductive polymer, is widely used in active layer materials due to its high conductivity, good thermal stability, strong oxidation resistance, and simple and environmentally friendly preparation methods.

[0005] At present, PDMS-based three-dimensional porous materials are widely used in the field of flexible piezoresistive sensors due to their excellent mechanical properties. Usually, PDMS-based three-dimensional porous materials are prepared using a sacrificial template method (salt template, sugar template). However, this method blends the template with PDMS or backfills PDMS into the template, and then dissolves the template to prepare a PDMS-based three-dimensional porous material. Although this method is low in cost, there is still a problem of template residue. The residual template will affect the mechanical properties of the material, thereby affecting other properties of the material. People have tried to use metal and other templates instead, but solvents such as strong acids must be used to dissolve the template, which has problems such as high cost, poor environmental protection and complex process. Therefore, it still cannot be widely recognized and used. Summary of the Invention

[0006] The purpose of the present invention is to provide a piezoresistive silicone rubber flexible sensor and a preparation method thereof, thereby overcoming the problems existing in the existing template method and preparing a PDMS-based three-dimensional porous material with excellent mechanical properties.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] The present invention provides a PDMS-based three-dimensional porous structure material, wherein the PDMS-based three-dimensional porous structure material is an AgNW / cPDMS sponge, and the AgNW / cPDMS sponge is prepared by the following preparation method:

[0009] (1) blending anionic hydroxy silicone oil emulsion and sodium carboxymethyl cellulose, and slowly stirring with a magnetic stirrer to obtain blend 1;

[0010] (2) blending the blend 1 with a silver nanowire dispersion to obtain a blend 2;

[0011] (3) adding the glutaraldehyde solution to the blend 2, stirring, and then adding the curing agent to blend to obtain blend 3;

[0012] (4) Blend 3 was placed in a glass container, then placed in a plastic centrifuge tube, and placed in a refrigerator for precooling;

[0013] (5) Freeze-drying was performed using a freeze dryer to obtain the AgNW / cPDMS sponge.

[0014] Preferably, for every 10 g of anionic hydroxy silicone oil emulsion, the corresponding amount of sodium carboxymethyl cellulose added is 0.045 g, the corresponding amount of silver nanowire dispersion added is 0.75 ml, the corresponding amount of glutaraldehyde solution added is 45 μl, and the corresponding amount of curing agent added is 0.3 g.

[0015] Preferably, in step (1), the stirring time of the magnetic stirrer is 2 hours;

[0016] In the step (2), the blending time is 0.5h;

[0017] In the step (3), the stirring time is 10 min and the blending time is 0.5 h;

[0018] In the step (4), the pre-cooling temperature of the refrigerator is -20°C, and the pre-cooling time of the refrigerator is 24 hours;

[0019] In the step (5), the freeze-drying temperature is -50°C and the freeze-drying time is 24 hours.

[0020] Secondly, the present invention provides a method for preparing a PDMS-based three-dimensional porous structure material, wherein the PDMS-based three-dimensional porous structure material is an AgNW / cPDMS sponge. The method for preparing the AgNW / cPDMS sponge comprises the following steps:

[0021] (1) blending anionic hydroxy silicone oil emulsion and sodium carboxymethyl cellulose, and slowly stirring with a magnetic stirrer to obtain a blend 1;

[0022] (2) blending the blend 1 with a silver nanowire dispersion to obtain a blend 2;

[0023] (3) adding the glutaraldehyde solution to the blend 2, stirring, and then adding the curing agent to blend to obtain blend 3;

[0024] (4) Blend 3 was placed in a glass container, then placed in a plastic centrifuge tube, and placed in a refrigerator for precooling;

[0025] (5) Freeze-drying was performed using a freeze dryer to obtain the AgNW / cPDMS sponge.

[0026] Preferably, for every 10 g of anionic hydroxy silicone oil emulsion, the corresponding amount of sodium carboxymethyl cellulose added is 0.045 g, the corresponding amount of silver nanowire dispersion added is 0.75 ml, the corresponding amount of glutaraldehyde solution added is 45 μl, and the corresponding amount of curing agent added is 0.3 g.

[0027] Preferably, in step (1), the magnetic stirring is performed slowly for 2 hours;

[0028] In the step (2), the blending time is 0.5h;

[0029] In the step (3), the stirring time is 10 min and the blending time is 0.5 h;

[0030] In the step (4), the pre-cooling temperature of the refrigerator is -20°C, and the pre-cooling time of the refrigerator is 24 hours;

[0031] In the step (5), the freeze-drying temperature is -50°C and the freeze-drying time is 24 hours.

[0032] Secondly, the present invention provides a Ppy / AgNW / cPDMS three-dimensional porous material, wherein the Ppy / AgNW / cPDMS three-dimensional porous material is a Ppy / AgNW / cPDMS sponge, and the preparation method of the Ppy / AgNW / cPDMS sponge is as follows:

[0033] (1) Cut the AgNW / cPDMS sponge into cubes;

[0034] (2) Dissolve FeCl3 in deionized water, add pyrrole and stir evenly to obtain a mixture 1;

[0035] (3) placing the cut AgNW / cPDMS sponge into the mixed solution 1 and slowly stirring with a magnetic stirrer to perform pyrrole deposition;

[0036] (4) The deposited cube was cleaned and dried in an oven to obtain a Ppy / AgNW / cPDMS sponge.

[0037] Preferably, the AgNW / cPDMS sponge is prepared by the preparation method of AgNW / cPDMS sponge;

[0038] The cube has a length, width and height of 1 cm;

[0039] The amount of deionized water added for every 0.1g of FeCl3 is 40ml, and the amount of pyrrole added is 150μl;

[0040] In the step (3), the stirring time is 1 h.

[0041] Secondly, the present invention provides a piezoresistive silicone rubber flexible sensor, wherein the piezoresistive silicone rubber flexible sensor is a Ppy / AgNW / cPDMS flexible sensor, and the Ppy / AgNW / cPDMS flexible sensor is prepared by the following preparation method:

[0042] (1) Using conductive silver paste, the cut copper foil is pasted on both sides of the Ppy / AgNW / cPDMS sponge to serve as electrodes;

[0043] (2) Connect the copper wire and the copper foil using conductive copper tape;

[0044] (3) Using PI tape to encapsulate the electrodes and the wire as a whole to obtain the Ppy / AgNW / cPDMS flexible sensor,

[0045] The Ppy / AgNW / cPDMS sponge is prepared by the preparation method of the Ppy / AgNW / cPDMS sponge according to claim 7.

[0046] The beneficial effects of the present invention are:

[0047] 1. The present invention uses the emulsion ice template method for the first time to prepare a PDMS-based three-dimensional porous structure material, and uses this material as the matrix to prepare a Ppy / AgNW / cPDMS piezoresistive flexible sensor. The use of this method to prepare PDMS three-dimensional porous materials effectively avoids template residue and solves the impact of template residue on the mechanical properties of the material. More importantly, the emulsion ice template method used in the present invention is simple, low-cost, environmentally friendly and green. The sensor prepared by the present invention has excellent sensing performance such as high sensitivity (GF=26.06), a wide monitoring range (70% strain) and good cyclic stability (3000 times at 30% strain). It can also monitor motion signals such as human joint bending and physiological signals such as pulse, and has broad application prospects in the field of human signal monitoring. In addition, thanks to the thermal sensitivity of Ppy, the sensor can also be used for temperature sensing, and has outstanding advantages in fields such as human body temperature monitoring and environmental temperature monitoring. Therefore, the preparation method and the sensor prepared provided by the present invention can be widely used in many fields such as flexible sensing.

[0048] 2. Sodium carboxymethyl cellulose (CMC) has multiple uses, improving the performance of PDMS-based three-dimensional porous materials. First, as an environmentally friendly hydrophilic material, CMC can act as a hydrophilic modifier for PDMS-based three-dimensional porous materials. Furthermore, CMC contains hydrophilic functional groups that effectively increase its interaction with water, improving the orientation of PDMS-based three-dimensional porous materials during pre-freezing and freeze-drying. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 Stereo microscope images of PDMS sponge (a) and cPDMS sponge (b);

[0050] Figure 2 is the contact angle of cPDMS sponge with different CMC concentrations;

[0051] Figure 3 Cross-sectional SEM images of PDMS sponge (a), cPDMS sponge (b-c), AgNW / cPDMS sponge (d-f), and Ppy / AgNW / cPDMS sponge (gi);

[0052] Figure 4 Digital photo of cPDMS sponge (a); stress-strain curves of PDMS sponge (b) and cPDMS sponge (c); stress-strain curve of cPDMS sponge after 100 cycles of 30% strain compression (d); stress-strain curve of AgNW / cPDMS sponge (e); stress-strain curve of AgNW / cPDMS sponge after 100 cycles of 30% strain compression (f);

[0053] Figure 5 Stress-strain curve of Ppy / AgNW / cPDMS sponge (a) and stress-strain curve after 100 cycles of 30% strain compression (b);

[0054] Figure 6 Sensitivity curve of the Ppy / AgNW / cPDMS sensor (a), sensing mechanism (b), response time of relative current change during rapid loading and release (c), and relative current change after 3000 repeated loading and release at 30% (d);

[0055] Figure 7 Relative current signal changes of the Ppy / AgNW / cPDMS sensor when the wrist is bent (a), the finger is bent (b), walking (c), and the finger is pressed (d);

[0056] Figure 8 Relative current signal changes of the Ppy / AgNW / cPDMS sensor when saying "hello" (a) and "polymer" (b) and measuring pulse (c);

[0057] Figure 9 Figure 3. Relationship between temperature and relative resistance of Ppy / AgNW / cPDMS sensor (a); change in resistance when temperature changes (b); and stability of temperature sensing (c). DETAILED DESCRIPTION

[0058] The present invention is further described below with reference to specific examples. The examples of the present invention are only used to explain the present invention and are not intended to limit the scope of protection of the present invention.

[0059] Example 1: Preparation of PDMS three-dimensional porous material

[0060] 1. Blend 10 g of anionic hydroxy silicone oil emulsion (solid content 30%) with 0.3 g of curing agent and stir slowly for 2 h using magnetic stirring to obtain blend 1;

[0061] 2. Pour Blend 1 into a 10 ml glass bottle (22 x 50 mm) and place the bottle into a centrifuge tube. Pre-freeze the centrifuge tube in a -20°C freezer for 24 hours.

[0062] 3. Freeze-dry the product at -50°C and low pressure for 24 h using a freeze dryer to obtain a three-dimensional porous material, named PDMS sponge.

[0063] Example 2: Preparation of cPDMS three-dimensional porous material

[0064] 1. Blend 10 g of anionic hydroxy silicone oil emulsion (solid content 30%) with 0.015 g, 0.030 g, and 0.045 g of sodium carboxymethyl cellulose (CMC), respectively, and slowly stir for 2 h using a magnetic stirrer to obtain blend 1;

[0065] 2. Add 0.3 g of curing agent and 15 μl, 30 μl, and 45 μl of glutaraldehyde solution (50% concentration) to blend 1, respectively, and slowly stir for 0.5 h using a magnetic stirrer to obtain blend 2;

[0066] 3. Pour Blend 2 into a 10 ml glass bottle (22 x 50 mm) and place the bottle into a centrifuge tube. Pre-freeze the centrifuge tube in a -20°C freezer for 24 hours.

[0067] 4. Freeze-dry the prepared product at -50°C and low pressure for 24 h to obtain a three-dimensional porous material, named cPDMS sponge.

[0068] Example 3: Preparation of AgNW / cPDMS three-dimensional porous materials

[0069] 1. Blend 10 g of anionic hydroxy silicone oil emulsion (solid content 30%) with 0.045 g (1.5 wt% of the dry rubber mass) of sodium carboxymethyl cellulose (CMC) and stir slowly with a magnetic stirrer for 2 h to obtain blend 1;

[0070] 2. Mixture 1 was blended with 0.75 ml of silver nanowire dispersion. After blending for 0.5 h, the silver nanowires were evenly dispersed to obtain blend 2.

[0071] 3. Add 45 μl of glutaraldehyde solution to blend 2 and stir for 10 min. Then add 0.3 g of curing agent and blend for 0.5 h to obtain the final blend 3.

[0072] 4. Pour blend 3 into a glass bottle, place it in a plastic centrifuge tube, and pre-freeze it in a -20°C refrigerator for 24 hours;

[0073] 5. Freeze-dry the sample at -50°C and low pressure for 24 h using a freeze dryer to obtain a three-dimensional porous material, named AgNW / cPDMS sponge.

[0074] Example 4: Preparation of Ppy / AgNW / cPDMS three-dimensional porous materials

[0075] 1. Cut the prepared AgNW / cPDMS sponge into cubes with a length, width and height of about 1 cm and set aside;

[0076] 2. Dissolve 0.1g FeCl3 in 40ml deionized water, add 150μl pyrrole, and stir well;

[0077] 3. Place the AgNW / cPDMS sponge cube into the solution and stir slowly for 1 hour using magnetic stirring. During the stirring process, press the cube with a glass rod every 10 minutes to allow Ppy to be better deposited on the internal skeleton material.

[0078] 4. Clean the deposited cube and dry it in an oven to obtain the Ppy / AgNW / cPDMS sponge.

[0079] Example 5: Preparation of Ppy / AgNW / cPDMS flexible sensor

[0080] 1. Use conductive silver paste to stick the cut copper foil on both sides of the Ppy / AgNW / cPDMS sponge as electrodes;

[0081] 2. Use conductive copper tape to connect the copper wire to the copper foil;

[0082] 3. Use PI tape to encapsulate the electrodes and wires as a whole to obtain a Ppy / AgNW / cPDMS flexible sensor.

[0083] Experimental Example 1

[0084] The structures of PDMS sponge and cPDMS sponge were detected. Figure 1 shown.

[0085] As can be seen from the figure, the PDMS sponge without CMC has relatively large pores. This is mainly due to the fact that the hydroxyl silicone oil emulsion has fewer active functional groups on its molecular chain, which cannot form a strong interaction with the water in the system. During the pre-freezing process, the growth of ice crystals is not restricted, resulting in ice crystal orientation and the formation of larger pores, which affects the mechanical properties of the material. In contrast, the cPDMS sponge prepared with CMC does not have large pores. The sponge has uniform pores, small pores, and no orientation.

[0086] Experimental Example 2

[0087] The contact angles of cPDMS sponges with different CMC concentrations were measured. Figure 2 shown.

[0088] As can be seen from the figure, the contact angle of the PDMS sponge without CMC is about 130°, indicating that the pure PDMS sponge is highly hydrophobic, which is not conducive to the deposition of Ppy in the later stage. When CMC is added, the contact angle of the water droplet when it contacts the sponge is basically the same as the contact angle of PDMS, but after about 0.5s of standing, the water droplet gradually penetrates into the sponge, and the contact angle also changes. Figure 2As shown in Figures (b,d), the contact angle of the cPDMS sponge changes significantly with increasing CMC concentration compared to the contact angle of the pure PDMS sponge. After standing, the sponge's contact angle reaches a minimum of 44°. This result demonstrates that the addition of CMC significantly improves the hydrophilicity of the cPDMS compared to the pure PDMS sponge.

[0089] Experimental Example 3

[0090] The cross-sectional SEM images of PDMS sponge, cPDMS sponge, AgNW / cPDMS sponge and Ppy / AgNW / cPDMS sponge were examined. Figure 3 shown.

[0091] Figure 3 (a) is a cross-sectional SEM image of a PDMS sponge, and (b) is a cross-sectional SEM image of a cPDMS sponge. As can be seen from the images, a three-dimensional open pore network with pore diameters of approximately tens of microns appears on the sponge cross section, demonstrating that freeze-drying can successfully prepare a PDMS sponge with a three-dimensional porous network structure. However, a comparison shows that the three-dimensional pore structure of the PDMS sponge differs somewhat from that of the cPDMS sponge. This is because the addition of CMC alleviates the orientation issues encountered during the preparation of the cPDMS sponge, resulting in a more complete pore structure. Figure 3 (df) are SEM cross-sectional images of AgNW / cPDMS sponge. Figure 3 Compared with (bc), AgNW / cPDMS sponge also has a three-dimensional porous structure, and the pore size is basically the same as that of cPDMS sponge. This result shows that the addition of silver nanowires does not affect the formation of the pore structure and its morphology. Figure 3 (f) It can be seen that the silver nanowires are attached to the surface of the PDMS skeleton and are randomly distributed in a linear manner. Finally, the cross section of the Ppy / AgNW / cPDMS sponge was characterized by SEM. Figure 3 (gh) It can be seen that the deposition of Ppy did not destroy the pore structure of the sponge, nor did it significantly change the pore size and morphology of the sponge. After magnification, it can be observed that the pore wall of the Ppy / AgNW / cPDMS sponge is relatively rough, and Ppy grows in a granular form on the PDMS skeleton ( Figure 3 (i)), demonstrating the successful deposition of polypyrrole.

[0092] Experimental Example 4

[0093] The mechanical properties of PDMS sponge, cPDMS sponge and AgNW / cPDMS were tested. The results are as follows Figure 4 shown.

[0094] Figure 4(b) and (c) show the stress-strain curves for PDMS and cPDMS sponges from 10% to 70% deformation, respectively. As can be seen from the figures, for both pure PDMS sponge and cPDMS sponge, stress gradually increases with increasing compressive strain, ultimately achieving a 70% deformation and stresses of 160 kPa and 350 kPa, respectively. Figure 4 (d) 100 compression-release cycles of the cPDMS sponge at 30% strain were performed to test the sponge's mechanical stability. As can be seen, after 100 compression cycles, the material's stress-strain and release curves are essentially identical and overlap, demonstrating that the sponge possesses both excellent mechanical properties and good mechanical stability.

[0095] The same test was conducted on AgNW / cPDMS sponge to test whether the addition of silver nanowires would affect the mechanical properties of the material. The results are as follows Figure 4 (ef) As shown. After adding silver nanowires, the compressive stress of the material also gradually increases with the compressive strain. After being compressed to 70% strain and releasing the pressure, the material can still recover. From the results, it can be seen that the stress-strain curve of AgNW / cPDMS sponge is basically consistent with the curve of cPDMS sponge, indicating that the addition of silver nanowires does not affect the mechanical properties of cPDMS sponge. The same results can also be seen in Figure 4 (f) Observed that in the 100-cycle compression test of 30% strain on the AgNW / cPDMS sponge, the material curve showed a similar curve to that of the cPDMS sponge, and the curves were also able to overlap with each other, with no obvious changes due to the compression cycle.

[0096] Experimental Example 5

[0097] The mechanical properties of Ppy / AgNW / cPDMS sponge were tested, and the results were as follows: Figure 5 shown.

[0098] As can be seen from the figure, after the deposition of polypyrrole, under the same strain, the Ppy / AgNW / cPDMS sponge is subjected to greater stress, which is caused by the rigidity of polypyrrole. However, the stress-strain curve of the Ppy / AgNW / cPDMS sponge can still be closed, proving that it can undergo corresponding mechanical deformation and has excellent mechanical properties. Subsequently, it was also subjected to 100 compression cycles at 30% strain to obtain a stress-strain curve. It can be seen from the results that the deposition of Ppy did not affect the mechanical stability of the sponge. The curves still overlap, proving that the mechanical stability of the Ppy / AgNW / cPDMS sponge is relatively excellent.

[0099] Experimental Example 6

[0100] The sensing performance of the Ppy / AgNW / cPDMS sponge sensor was tested, and the results were as follows Figure 6 shown.

[0101] Figure 6 (a) shows the corresponding ΔI / I0 vs. strain curve. As can be seen from the figure, the ΔI / I0 of the sensor increases continuously with increasing deformation. Based on the different rates of change of ΔI / I0, the sensitivity of the sensor can be divided into two regions. The first region has a strain range of 0-40% strain, within which the GF is 7.46, and the linear relationship is approximately 0.98. The second region is after 40% strain, where the sensitivity increases rapidly within this range, reaching GF of 26.06, but the linear relationship does not change significantly, remaining at around 0.96. Most importantly, the sensor's deformation range reaches 70%, meaning that the sensor's monitoring range reaches 70%. Combined with the mechanical properties mentioned above, it can be concluded that the sensor's monitoring range can exceed 400 kPa, indicating that it has a relatively wide monitoring range.

[0102] Then, a pressure is quickly applied to the sensor to achieve a strain of 30%, and its response time and relaxation time are recorded. The results are as follows: Figure 6 As shown in (b), the Ppy / AgNW / cPDMS sponge sensor exhibits excellent response characteristics. When the sensor is subjected to pressure, the sensor has a fast response time of 470ms. When the pressure applied to the sensor is removed, the relaxation time of the sensor is 335ms. In addition, to verify the cyclic stability of the sensor, the sensor was subjected to a 30% strain 3000 cycle compression test. The results are shown in Figure 2. Figure 6 (c) As shown. It can be seen that during the 3000 cycles, the electrical signal showed no significant fluctuations. Subsequently, the electrical signal of 10 compression cycles was intercepted at two time points. It can be observed that the waveforms of the electrical signals were basically the same. These results indicate that the sensor has good repeatability during the compression process, the skeleton material and the conductive active layer on the surface are not significantly damaged, and the sensor has excellent cyclic stability.

[0103] Experimental Example 7

[0104] The sensor is used to detect the effect of human wrist bending. Figure 7 shown.

[0105] exist Figure 7 In (a), the sensor is fixed to the wrist joint to monitor the bending movement of the human wrist. As can be seen from the figure, when the wrist is bent, the sensor is subjected to pressure and the relative current signal increases rapidly. When the wrist recovers, the electrical signal recovers quickly. Repeated wrist bending can produce similar electrical signals. Figure 7As shown in (b), the sensor is fixed on the finger. When the finger is bent at a bending and recovery angle of 0°-90°-0°, the sensor can generate a unique step-like relative current signal corresponding to different finger bending angles. These results show that the sensor can be used to monitor the bending activities of joints such as wrists and fingers, and is expected to be applied in the field of joint recovery and monitoring after surgery. Figure 7 As shown in (c), fixing the sensor on the sole of the foot can monitor a person's walking condition. As can be seen from the figure, when the volunteer's foot is lifted, the sensor's electrical signal is at a stable value. When the volunteer's foot contacts the ground, the sensor's relative current signal rises rapidly, and then drops when the foot leaves the ground. This result shows that the sensor can be used in areas such as monitoring walking frequency. Since the sensor can monitor pressure signals of different pressures and frequencies, the sensor can be applied to finger press signals, as shown in the following figure. Figure 7 (d) When a finger presses slowly and with greater force, the sensor generates a high-peak but low-frequency electrical signal. Conversely, when the sensor is pressed quickly and gently, it generates multiple high-frequency peaks with lower peaks. This sensor's application characteristics suggest its potential applications in fields such as human-computer interaction and signal transmission.

[0106] Experimental Example 8

[0107] The effect of the detection sensor when used to detect human physiological signals, the results are as follows Figure 8 shown.

[0108] like Figure 8 (ab), fix the sensor at the throat, and make the throat vibrate by saying "hello" and "polymer". The sensor generates different electrical signals according to the vibration of the throat. After repeated many times, the sensor can still generate relatively stable electrical signals, proving that it has certain application space in fields such as speech recognition. Fix the sensor at the pulse of the human wrist and use it to monitor the human pulse signal. Figure 8 (c) As can be seen, the sensor recorded a total of 15 pulse signals over 11 seconds, with an average pulse rate of one every 0.73 seconds. Calculations indicate that the volunteer's pulse rate during monitoring was 82 beats per minute, which is within the normal range. Furthermore, amplifying a single pulse signal reveals the three signature peaks of the impulse wave (P), tidal wave (T), and diastolic wave (D), demonstrating the potential application of this sensor in detecting human physiological signals.

[0109] Experimental Example 9

[0110] The effect of the sensor on temperature detection is as follows Figure 9 shown.

[0111] The Ppy / AgNW / cPDMS sensor was fixed on the surface of a beaker, and the sensor's response to temperature changes was detected by changing the temperature of the water in the beaker. Figure 9 (a) is the ΔR / R0 change of the Ppy / AgNW / cPDMS sensor at temperatures of 20-55°C. After fitting calculations, it can be concluded that the TCR value of the Ppy / AgNW / cPDMS sensor is 0.69% / °C, which exceeds the TCR of commercial platinum temperature sensors (0.392% / °C). Subsequently, the rapid response capability of the sensor was tested by alternately adding water at 20°C and 40°C to the beaker. The results are shown in the figure. Figure 9 As shown in (b). It can be seen that when 40℃ water is added to the beaker, the relative resistance of the sensor drops rapidly, and after about 1 minute, the relative resistance tends to be stable. When 20℃ water is added to the beaker, the electrical signal rises rapidly and eventually tends to be stable. Finally, to further test the stability of the sensor's temperature sensing, water at 20℃ and 40℃ is alternately added to the beaker 10 times, and the change in the electrical signal is recorded. Figure 9 As shown in (c), the ΔR / R0 value of the sensor did not show significant differences after 10 cycles of hot / cold cycling, indicating that the Ppy / AgNW / cPDMS temperature sensor has high repeatability and stability. These results indicate that the sensor has broad application prospects in temperature detection and other fields, such as human body temperature monitoring.

Claims

1. A PDMS-based three-dimensional porous structure material, characterized in that: The PDMS-based three-dimensional porous structure material is AgNW / cPDMS sponge, and the AgNW / cPDMS sponge is prepared by the following preparation method: (1) Blending anionic hydroxy silicone oil emulsion and sodium carboxymethyl cellulose, and slowly stirring with a magnetic stirrer to obtain a blend 1; (2) blending the blend 1 with a silver nanowire dispersion to obtain a blend 2; (3) adding the glutaraldehyde solution to the blend 2, stirring, and then adding a curing agent to blend to obtain a blend 3; (4) Blend 3 was placed in a glass container, then placed in a plastic centrifuge tube, and placed in a refrigerator for precooling; (5) Freeze-drying was performed using a freeze dryer to obtain AgNW / cPDMS sponge.

2. The PDMS-based three-dimensional porous structure material according to claim 1, characterized in that: For every 10 g of anionic hydroxy silicone oil emulsion, the corresponding amount of sodium carboxymethyl cellulose added is 0.045 g, the corresponding amount of silver nanowire dispersion added is 0.75 ml, the corresponding amount of glutaraldehyde solution added is 45 μl, and the corresponding amount of curing agent added is 0.3 g.

3. The PDMS-based three-dimensional porous structure material according to claim 1, characterized in that: In the step (1), the stirring time of the magnetic stirrer is 2 hours; In the step (2), the blending time is 0.5h; In the step (3), the stirring time is 10 minutes and the blending time is 0.5 hours; In step (4), the pre-cooling temperature of the refrigerator is -20 ° C, and the pre-cooling time of the refrigerator is 24 hours; In the step (5), the freeze-drying temperature is -50 °C and the freeze-drying time is 24 hours.

4. A method for preparing a PDMS-based three-dimensional porous structure material, characterized in that: The PDMS-based three-dimensional porous structure material is an AgNW / cPDMS sponge, and the preparation method of the AgNW / cPDMS sponge comprises the following steps: (1) Blending anionic hydroxy silicone oil emulsion and sodium carboxymethyl cellulose, and slowly stirring with a magnetic stirrer to obtain a blend 1; (2) blending the blend 1 with a silver nanowire dispersion to obtain a blend 2; (3) adding the glutaraldehyde solution to the blend 2, stirring, and then adding a curing agent to blend to obtain a blend 3; (4) Blend 3 was placed in a glass container, then placed in a plastic centrifuge tube, and placed in a refrigerator for precooling; (5) Freeze-drying was performed using a freeze dryer to obtain AgNW / cPDMS sponge.

5. The preparation method according to claim 4, characterized in that For every 10 g of anionic hydroxy silicone oil emulsion, the corresponding amount of sodium carboxymethyl cellulose added is 0.045 g, the corresponding amount of silver nanowire dispersion added is 0.75 ml, the corresponding amount of glutaraldehyde solution added is 45 μl, and the corresponding amount of curing agent added is 0.3 g.

6. The preparation method according to claim 4, characterized in that In the step (1), the magnetic stirring is carried out slowly for 2 hours; In the step (2), the blending time is 0.5h; In the step (3), the stirring time is 10 minutes and the blending time is 0.5 hours; In the step (4), the pre-cooling temperature of the refrigerator is -20°C, and the pre-cooling time of the refrigerator is 24 hours; In the step (5), the freeze-drying temperature is -50°C and the freeze-drying time is 24 hours.

7. A Ppy / AgNW / cPDMS three-dimensional porous material, characterized in that: The Ppy / AgNW / cPDMS three-dimensional porous material is a Ppy / AgNW / cPDMS sponge, and the preparation method of the Ppy / AgNW / cPDMS sponge is as follows: (1) Cutting the AgNW / cPDMS sponge into cubes, wherein the AgNW / cPDMS sponge is prepared by the preparation method according to any one of claims 4 to 6; (2) Dissolve FeCl3 in deionized water, add pyrrole and stir evenly to obtain a mixture 1; (3) placing the cut AgNW / cPDMS sponge into the mixed solution 1 and slowly stirring with a magnetic stirrer to perform pyrrole deposition; (4) The deposited cube was cleaned and placed in an oven for drying to obtain a Ppy / AgNW / cPDMS sponge.

8. The Ppy / AgNW / cPDMS three-dimensional porous material according to claim 7, characterized in that The AgNW / cPDMS sponge is prepared by the preparation method of the AgNW / cPDMS sponge according to claim 4; The cube has a length, width and height of 1 cm; The amount of deionized water added for every 0.1g of FeCl3 is 40ml, and the amount of pyrrole used is 150μl; In the step (3), the stirring time is 1 h.

9. A piezoresistive silicone rubber flexible sensor, characterized in that: The piezoresistive silicone rubber flexible sensor is a Ppy / AgNW / cPDMS flexible sensor, which is prepared by the following preparation method: (1) Use conductive silver paste to stick the cut copper foil on both sides of the Ppy / AgNW / cPDMS sponge to act as electrodes; (2) Use conductive copper tape to connect the copper wire to the copper foil; (3) Using PI tape to encapsulate the electrodes and wires as a whole to obtain the Ppy / AgNW / cPDMS flexible sensor; The Ppy / AgNW / cPDMS sponge is the Ppy / AgNW / cPDMS sponge according to claim 7.

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