Self-Sensing IPMC Artificial Muscle and Its Preparation Method

Abstract

The present invention discloses a self-sensing IPMC artificial muscle and its preparation method, which consists of a driving layer, a transition layer, a sensing layer, an external driving signal module and a sensor acquisition module. The transition layer is located between the driving layer and the sensing layer. The driving layer is connected to the driving signal module, and the sensing layer is connected to the sensor acquisition module. On the basis of preparing IPMC with a Nafion membrane as the substrate and Pt nanoparticles as the surface electrodes, it is first encapsulated with PVP@AgNPs, then coated with a flexible PMVS polyvinylsiloxane for encapsulation, and finally the interdigitated pattern electrodes are bonded. The self-sensing IPMC artificial muscle proposed by the present invention can realize the integration of driving and sensing. The IPMC moves under the excitation of an electric field, and the movement of the IPMC causes the change of the distance between the interdigitated capacitors on its surface, thus causing the change of capacitance. The change of capacitance can be collected at any time by using a single-chip microcomputer and Bluetooth to realize the monitoring of the movement of the IPMC.

Description

Technical Field

[0001] The present invention belongs to the technical field of driver preparation, and particularly relates to a self-sensing IPMC artificial muscle and a preparation method thereof. Background Art

[0002] A self-sensing driver has both the functions of a driver and a sensor, and has significant advantages such as small volume and high intelligence, and is very useful in national defense, civil use, medical treatment, health care, etc. At the same time, the drive signal control and the acquisition of the sensing signal of the self-sensing driver can be carried out synchronously, and remote on-line detection can also be realized, further expanding the application space.

[0003] Ion-exchange polymer / metal composite (IPMC) is an ionic electro-driver that can directly convert electrical energy into mechanical energy without using a motor ( Figure 2 ). IPMC usually consists of a three-layer sandwich structure. The two sides are metal nanoparticle electrodes, such as Pt, Au, Ag; the sandwich layer is an ion-exchange polymer membrane, such as perfluorosulfonic acid, perfluorocarbonic acid, sulfonated polysulfone, polyether ether ketone, etc. IPMC is a flexible driver and can be used to make a flexible driver. Because its driving performance is similar to that of natural muscles, it is also known as an "artificial muscle". Within a certain range, IPMC can replace the motor as an electro-driver. Compared with the motor: the IPMC driver has high energy conversion efficiency, large displacement, large energy density, and does not have the problems of the volume and heat generation of the motor.

[0004] The IPMC driver can also be used as a self-sensing driver. Under external mechanical stimulation, IPMC deforms, causing the movement of cations and anions at both poles, resulting in an unbalanced distribution of surface charges and generating an induced voltage, which can be used as a displacement / resonance sensor. However, this IPMC sensor has four obvious defects: (1) the induced voltage signal is very weak, between microvolts and millivolts; (2) the sensing signal is not sensitive, and only when the IPMC undergoes a large deformation can a weak electrical signal be collected; (3) the response is slow. The response rate of this sensor depends on the migration rate of internal electrolyte ions. Due to the large volume of ions, they are subject to a large viscous resistance during movement and cannot migrate quickly; (4) the signal-to-noise ratio is poor. Factors such as deformation, temperature, humidity, and acidity that cause ion movement are mixed together and all affect the induced voltage. Therefore, it is difficult for the IPMC sensor to truly reflect the displacement / vibration information and cannot truly achieve the integration of driving / sensing.

[0005] The interdigital pattern electrode is a large-area capacitor. Its capacitance can be obtained according to the following formula:

[0006]

[0007] In the formula, c is the capacitance; A is the area of the pattern electrode, and d is the distance between the electrodes.

[0008] After fixing the interdigital pattern electrodes on the surface of the IPMC, when the IPMC film moves, the distance between the surface pattern electrodes changes, thus generating a capacitance change to respond to the occurring deformation. Since the IPMC itself can generate deformation and can be used as a driving source to drive the capacitance change. Therefore, the deflection angle of the IPMC can be reflected by the capacitance signal. Thus, the IPMC with fixed pattern electrodes can act as a self-sensing electric driver.

[0009] The structural parameters of the planar interdigital electrode sensor mainly include the number of fingers N, the finger length L, the finger spacing s, and the finger width w. Changes in the structure will change the electrical parameters of the electrode itself. The parameter optimization of the interdigital structure electrode can be quantitatively compared based on its conduction ability to the dielectric. Therefore, the unit constant C can be defined K to characterize the relationship between the impedance measured by the sensor and the characteristic impedance of the dielectric:

[0010]

[0011] In the formula, K(k) is the first-order elliptic integral. And

[0012]

[0013] Theoretically speaking, the smaller the unit constant C K is, the higher the sensitivity of the sensor. From the formula of C K it can be seen that the more the number of fingers N, the larger the finger length L, and the smaller the finger width w, the smaller the unit constant, and the stronger the conduction ability of the interdigital sensor.

[0014] After retrieval, regarding the repair of IPMC, the relevant work is as follows:

[0015] (1) The Tan team at the University of Michigan in the United States proposed using a parylene coating to increase the water retention performance (Sensors and Actuators A 217(2014)1–12), prevent electrode and wire corrosion, and work in various environments. This encapsulation method has a good water retention effect, but long-term operation may cause bubbling, resulting in the separation of the coating from the IPMC.

[0016] (2) ZL 202011494435.8 proposed electroplating a layer of PEDOT molecular film on the surface of the old IPMC for encapsulation. PEDOT fills inside and on the surface of the IPMC electrodes, and has a good repair effect on the fatigue of the IPMC electrodes. However, this method requires controlling very fine experimental conditions to ensure that PEDOT exists in the form of a polymer film rather than in the form of particles.

[0017] (3) ZL 202011494435.8 proposes to coat the surface of the old IPMC with PVP@AgNPS particles for the repair of IPMC. This method is simple and effective. Especially after the used waste IPMC is treated, it can realize the function of turning waste into new. However, the PVP@AgNPS particles cannot completely prevent the loss of water solvent from the gaps between the particles. After continuous operation for a long time, the IPMC still needs to be replenished with water.

[0018] After retrieval, in the self-sensing aspect of IPMC, it focuses on resistive sensors and does not involve the self-sensing of capacitive sensors. The related work is as follows:

[0019] (1) The Dutchman Punning proposed to use the resistance change generated when the IPMC bends to detect the bending angle of the IPMC (Sensors and Actuators A, 2007, 136, 656 - 664). The sensitivity of this impedance sensor is one order of magnitude stronger than that of the induced voltage type sensor, and it shows a high signal-to-noise ratio.

[0020] (2) The German Punning proposed that Bakhtiarpour proved the linear relationship between the resistance signal and the bending angle of the IPMC in the high-frequency region. Further pointed out that this impedance sensor has high anti-interference and reliability. Summary of the Invention

[0021] Aiming at the problems existing in the prior art, the present invention provides a preparation method of a self-sensing ion-exchange polymer / metal composite (IPMC) artificial muscle. The present invention integrates a capacitive sensor on the driving surface of the IPMC to obtain an IPMC self-sensing actuator with high sensitivity, fast response, and stable and adjustable driving.

[0022] To solve the above technical problems, the present invention adopts the following technical solutions:

[0023] A self-sensing IPMC artificial muscle is composed of a driving layer, a transition layer, a sensing layer, an external driving signal module, and a sensor acquisition module. Among them, the transition layer is located between the driving layer and the sensing layer. The driving layer is connected to the driving signal module, and the sensing layer is connected to the sensor acquisition module.

[0024] Furthermore, the driving layer is an IPMC electro-actuator prepared by chemical deposition with a Nafion membrane as the base membrane and Pt nanoparticles as the electrodes. The thickness of the base membrane is 100 - 300 μm, and the thickness of the electrodes is 5 - 10 μm.

[0025] Further, the transition layer is composed of a PVP@AgNPS coating and a polyvinylsiloxane (PMVS) film. Among them, the thickness of the PVP@AgNPS coating (PVP@AgNPs electrode encapsulation layer) is 0.5 - 5 μm, and the thickness of the polyvinylsiloxane (PMVS) film is 20 - 100 μm.

[0026] Further, the sensing layer is composed of interdigital pattern electrodes, and the thickness of the sensing layer is 10 - 100 μm.

[0027] Further, the driving signal module is a low - voltage alternating current signal, with a frequency of 0.1 - 10 Hz, a driving voltage of 0.5 - 5 V, and the waveform is a sine wave or a square wave; the sensor acquisition module is composed of a commercial single - chip microcomputer and Bluetooth, and can collect capacitance signals in real - time online.

[0028] The above self - sensing IPMC artificial muscle is based on preparing IPMC with a Nafion membrane as the substrate and Pt nanoparticles as the surface electrodes. First, it is encapsulated with PVP@AgNPs ( Figure 4 ), then a flexible PMVS polyvinylsiloxane is coated for encapsulation, and finally, interdigital pattern electrodes are bonded.

[0029] Further, for the preparation method of the self - sensing PMC artificial muscle of the present invention, IPMC prepared by encapsulating Pt particle electrode layers on both sides of a Nafion substrate film by electroless plating process is selected. Then, a dense layer of silver nanoparticles wrapped with polyvinylpyrrolidone (PVP@AgNPs) material is encapsulated on the surface of the IPMC electrode by dip - coating technology. Next, a flexible PMVS polyvinylsiloxane is coated on the IPMC surface by a spin coater to encapsulate the interdigital pattern electrodes.

[0030] The preparation method of the self - sensing IPMC artificial muscle is as follows:

[0031] (1) PVP@AgNPs encapsulation method: Place a small beaker filled with a solution of silver nanoparticles wrapped with PVP (PVP@AgNPs) on the floating platform of a large beaker with holes at the bottom and filled with liquid. Immerse the selected Pt - electrode IPMC into the solution of silver nanoparticles wrapped with PVP. Control the descending speed of the floating platform by controlling the outflow speed of the liquid in the large beaker. The small beaker descends as the floating platform descends, thereby achieving a pulling effect on the IPMC in the beaker, and thus uniformly suspending a layer of silver nanoparticles wrapped with PVP on the Pt electrode on the surface of the IPMC, that is, obtaining a PVP@AgNPs - encapsulated IPMC electro - actuator.

[0032] After pulling, silver nanoparticles can easily fill the defects of the Pt electrode. The bonding between Ag nanoparticles and Pt nanoparticles is stronger, the electrode is not easy to fall off, and the encapsulation effect on IPMC is more significant, thereby extending the working time of the IPMC actuator, reducing the electrode fatigue of the IPMC actuator, and thus improving the output force, displacement and mechanical properties of the IPMC. The pulling speed of the pulling process is 4-6mm / 5min, and the concentration of the PVP-coated silver nanoparticle solution (PVP@AgNPs dispersed in an ethanol solution) is 1.0-5.0g / L.

[0033] Furthermore, a layer of flexible polyvinylsiloxane PMVS was coated on the surface of the prepared PVP@AgNPs-encapsulated IPMC using a glue spreader, and the thickness after curing was between 10-100μm. The purpose of covering with PMVS glue is to encapsulate IPMC and bond pattern electrodes. The isolated alkenyl groups contained in polyvinylsiloxane (PMVS) make it flexible. The polyvinylsiloxane PMVS layer coated on the surface of IPMC is very compatible with the polyvinylpyrrolidone wrapped on the silver nanoparticles encapsulated on the surface of IPMC. The electrodes are not easy to fall off, and bubbling is not easy to occur. It can also prevent water from being lost from the gaps between PVP@AgNPs particles, which has a good water retention effect, thereby extending the actuation time of IPMC.

[0034] (2) Interdigital pattern electrode packaging method:

[0035] (a) Electrode preparation: Weigh 5 g of each component A and B of conductive silicone (Wacker Chemicals, USA) and place them in a beaker, then add 7.5 g of silicone oil to each component, stir the two components thoroughly to make them completely dissolved in the silicone oil, then mix the two components, continue stirring, and then store them at low temperature (-5-20°C).

[0036] (b) Electrode coating. Figure 7 As shown, the PET film is cut into 6×6 mm rectangles by laser cutting. The PVC film is spread flat on a plastic culture dish, bubbles are eliminated, the cut PET film is attached to the PVC film, and then the prepared AB electrode is coated on the rectangular part of the PET film. The PET film is peeled off, and the PVC film coated with the AB electrode is spread flat on the plastic culture dish and placed in an oven for drying. After drying, take it out and use tweezers to remove the formed electrode film for storage.

[0037] (c) Pattern electrode etching: A CO2 laser etcher with a maximum power of 60 kW and a computer-controlled output power of 55% is used to etch interdigitated pattern electrodes on the electrode film.

[0038] (d) Pattern electrode packaging: The interdigitated pattern electrodes are thermally bonded and symmetrically attached to the surface of the PMVS-encapsulated IPMC, and then dried and cured.

[0039] Advantages of the present invention: The self-sensing IPMC artificial muscle proposed by the present invention improves the actuation performance of the IPMC electro-actuator. The PVP@AgNPs particles are coated on the surface electrodes of the IPMC. The Ag nanoparticles fill the gaps on the surface of the Pt electrodes, preventing the electrodes from falling off, providing better encapsulation of the IPMC, reducing electrode fatigue, thereby improving the output force, displacement and mechanical properties of the IPMC, and having a stable working state.

[0040] The self-sensing IPMC artificial muscle proposed by the present invention has an extended actuation time. The polyvinylsiloxane PMVS layer coated on the surface of the IPMC has good compatibility with the silver nanoparticles encapsulated on the surface of the IPMC and wrapped with polyvinylpyrrolidone. The electrodes are not easy to fall off and do not easily generate bubbling phenomena. It can also prevent moisture from leaking through the gaps between the PVP@AgNPs particles, achieving a good water retention effect, thereby extending the actuation time of the IPMC in air. The PMVS layer can also serve the purpose of stably bonding the subsequent pattern electrodes.

[0041] The drive system and the sensing system of the self-sensing IPMC artificial muscle proposed by the present invention do not interfere with each other. The capacitive sensor is an interdigital polydimethylsiloxane (PDMS) pattern electrode, which can be effectively bonded to the surface of the PMVS without falling off. Due to the isolation of the PMVS, the drive signal and the sensing signal become two independent systems. Without signal filtering, the sensing signal can be separated with high accuracy.

[0042] The self-sensing IPMC artificial muscle proposed by the present invention can achieve the integration of drive and sensing. The IPMC moves under the excitation of an electric field, and the movement of the IPMC causes a change in the distance between the interdigital capacitors on its surface, thereby causing a change in capacitance. The change in capacitance can be collected at any time using a single-chip microcomputer and Bluetooth to monitor the movement of the IPMC. Brief Description of the Drawings

[0043] Figure 1 Schematic cross-sectional structure diagram of the self-sensing IPMC (only one side of the electrode is shown, and the other side is symmetrically distributed).

[0044] Figure 2 Schematic diagram of the IPMC actuation mechanism.

[0045] Figure 3 TEM image of the PVP@AgNPs particles.

[0046] Figure 4 Schematic diagram of the IPMC encapsulation. Encapsulation process of AgNPs and PMVS (a); Coating process of AgNPs (b); Spin coating process of PMVS (c).

[0047] Figure 5 Parameter identification diagram of the interdigital electrode sensor.

[0048] Figure 6 Design diagrams of four planar interdigital electrode sensor structures.

[0049] Figure 7 Preparation of self-sensing IPMC artificial muscle. Schematic diagram of laser etching of patterned electrodes (a); Physical picture of self-sensing IPMC artificial muscle (b).

[0050] Figure 8 Strain sensing of patterned electrodes on the IPMC surface. IPMC deformation-capacitance measurement device (a); Single-chip microcomputer and Bluetooth device for auxiliary capacitance signal acquisition (b); Comparison diagram of deformation collected by laser displacement sensor and capacitance collected by single-chip microcomputer (c).

[0051] Figure 9 Continuous electroactuation screenshot of IPMC with encapsulated patterned electrodes.

[0052] Figure 10 Capacitance output curve of self-sensing IPMC artificial muscle. Capacitance curve on the surface of the artificial muscle within 200 seconds under a current excitation of 3.0V and 0.5Hz (a); and local capacitance curve (b). Specific implementation manners

[0053] The following further describes the present invention in conjunction with specific embodiments. It should be understood that the following embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. Those skilled in the art can make some non-essential improvements and adjustments based on the content of the above invention.

[0054] Embodiment 1

[0055] Select an IPMC prepared by encapsulating Pt particle electrode layers on both sides of a Nafion substrate film by electroless plating process, where the thickness of the substrate film is 100 - 300μm and the thickness of the electrode is 5 - 10μm. The driving performance test of the IPMC is shown in Table 3.

[0056] PVP@AgNPs encapsulation

[0057] Add PVP@AgNPs particles into an ethanol solution to prepare a solution with a concentration of 1.0 - 5.0 g / L. As Figure 4 shown, place the solution on the floating platform of a large beaker with holes at the bottom, control the liquid outflow rate of the large beaker (ensure that the descending speed of the floating platform is 4 - 6 mm / 5 min), so as to achieve the effect of lifting. After one lifting, put it into an oven at 60°C for drying, and repeat the lifting operation 1 - 6 times. After drying, the PVP@AgNPs-encapsulated IPMC electroactuator is obtained. The surface resistance before and after PVP@AgNPs coating is measured by a four-probe resistance meter, and the results are shown in Table 1.

[0058] Table 1 Sheet Resistance of Electrodes

[0059]

[0060] Design of Interdigitated Pattern Electrodes in Example 2

[0061] As Figure 6 shown, the structural parameters of the planar interdigitated electrode sensor mainly include the number of fingers N, the finger length L, the finger spacing s, and the finger width w. In the present invention, four sensors (a - d) with different structural parameters were designed, as shown in Table 2.

[0062] Table 2 Comparison of Structural Parameters of Different Sensors

[0063]

[0064]

[0065] Example 3 Encapsulation of Interdigitated Pattern Electrodes

[0066] (a) Electrode preparation. Weigh 5 g of each of the two components of conductive silicone (Wacker Chemicals, USA), A and B electrodes, and place them in a beaker. Then add 7.5 g of silicone oil to each, stir the two components thoroughly to dissolve them completely in the silicone oil, then mix the two components and continue stirring, and then store them in a low - temperature environment.

[0067] (b) Electrode coating. As Figure 7 shown, use the laser cutting method to cut out the required electrode pattern on the PET film, stick the cut PET film on the PVC film, and then coat the prepared AB electrode on the patterned part of the PET film. Peel off the PET film, lay the PVC film flat on a plastic petri dish, and put it in an oven to dry.

[0068] (c) Pattern etching. Use a CO2 laser etcher with a maximum power of 60 kW, and control the output power at 55% at the computer end to etch the pattern electrode on the electrode film.

[0069] (d) Pattern electrode encapsulation. As Figure 4 shown, use a spin coater to coat a layer of flexible polyvinylsiloxane PMVS on the surface of the fabricated PVP@AgNPs - encapsulated IPMC, then use thermal bonding to symmetrically attach it to the IPMC surface, and then dry and cure it. At this time, the driving performance test results are shown in Table 6 and Figure 8 . The results show that: the working displacement of the IPMC artificial muscle is 0.5 - 9.3 mm, the stable working time is 0.5 - 56 minutes, and the output force change range is 2.2 - 12.1 mN.

[0070] Electromechanical Property Characterization of IPMC

[0071] (1) Experimental setup: It mainly consists of a signal generation unit, a signal amplification unit, and a force sensor. The hardware of the signal generation unit is composed of a 6024E multifunctional data acquisition card from National Instruments Corporation; the software is obtained through LabVIEW programming; the signal amplification unit is composed of a power amplification chip OPA548 from Texas Instruments; the force sensor selected is a one-dimensional force sensor that can measure micro-Newton levels. The voltage signal measured by the force sensor passes through an amplification circuit and is then read into the computer by the 6024E multifunctional data acquisition card, and the force signal is obtained after processing.

[0072] (2) Electro - actuation performance test: Place the IPMC between the two poles of the power supply, control the voltage to be between 0.5 - 5V, and the working frequency to be between 0.1 - 10Hz. Use a high - speed camera (Olympus) and a laser displacement sensor (Keynce) to observe the displacement of the electro - actuator and the working time of the material, measure the magnitude of the output force with a force sensor, and compare the force and displacement outputs and the working time. The results are listed in Tables 3, 4, 5, and 6.

[0073] Table 3 Electro - actuation performance of IPMC

[0074]

[0075] The driving performance test of IPMC is shown in Table 3. The results show that: the surface resistance of IPMC is between 0.5 - 3.6Ω / sq (Table 1); the working displacement of the IPMC artificial muscle is 1.3 - 18.1mm, the stable working time is 0.2 - 25 minutes, and the output force variation range is 0.2 - 29.6mN.

[0076] Table 4 Electro - actuation performance of IPMC (encapsulated with PVP@AgNPs)

[0077]

[0078] The driving performance test of IPMC encapsulated with PVP@AgNPs is shown in Table 4. The results show that: the surface resistance is between 0.3 - 0.9Ω / sq (Table 1); the working displacement of the IPMC artificial muscle is 0.8 - 15.7mm, the stable working time is 0.3 - 38 minutes, and the output force variation range is 0.3 - 41.1mN.

[0079] Table 5 Electro - actuation performance of IPMC (encapsulated with PMVS)

[0080]

[0081] A flexible polyvinylsiloxane PMVS was coated on the surface of the fabricated PVP@AgNPs encapsulated IPMC using a spin coater. At this time, the driving performance test is shown in Table 5. The results show that the working displacement of the IPMC artificial muscle is 0.4 - 12.1 mm, the stable working time is 0.5 - 56 minutes, and the output force variation range is 3.3 - 22.8 mN.

[0082] Table 6 Electro - actuation performance of IPMC (pattern electrode encapsulated)

[0083]

[0084] Sensing performance characterization

[0085] As Figure 8 shown, the test device of the sensor consists of four parts: a driving part, an IPMC with a fixed pattern electrode, a single - chip microcomputer, and a computer terminal. The driving source comes from a commercial linear motor. The end of the IPMC film is pushed by the motor at angles of 10°, 20°, and 50°, causing a change in the distance between the two electrodes of the surface capacitor. The single - chip microcomputer can directly calculate the capacitance signal. The pattern electrode in the embodiment is connected to the Arduino single - chip microcomputer with a wire to form a circuit, and the collected capacitance signal can be directly transmitted to the computer wirelessly. The results are shown in Table 7. As the deflection angle increases, the capacitance of all four capacitors increases. The change range of the capacitor is between 11 - 145 pF.

[0086] Table 7 Capacitance change of pattern electrodes with different structural parameters (capacitance / pF)

[0087] 10° 20° 50° Sensor-a 20 42 145 Sensor-b 16 35 130 Sensor-c 13 30 121 Sensor-d 11 24 116

[0088] Self - sensing performance characterization

[0089] In Figure 8 the device, a signal generator is directly used as the power source instead of the motor to drive the IPMC to move, thereby generating a capacitance change. The signal generator can change sine, square wave, and triangular wave signals at voltages from 0 to 5.0 V and frequencies from 0.1 to 100 Hz. The capacitance change of pattern electrode a during the movement of the IPMC within 200 s is collected and listed in Figure 10 . The results show that under the electrical excitation of 2.5 V and 0.5 Hz, the IPMC generates a stable deflection angle of about 48°, and capacitor a generates a stable and periodic capacitance output, with an average capacitance of 75 F. The long - term capacitance signal indicates that the self - sensing artificial muscle has good repeatability and reliability.

[0090] With the assistance of an external microcontroller and Bluetooth, the capacitance data of the pattern electrode is input into a computer. When the deflection angle varies in the range of 10 - 50°, the capacitance of the sensor changes in the range of 11 - 145 pF. Under the current excitation of 3.0V and 0.5Hz, the IPMC artificial muscle bends, and the sensor collects stable and periodic capacitance change data( Figure 10 ).

[0091] The self-sensing IPMC artificial muscle of the present invention has the following technological advancements:

[0092] (1) The sensor has high sensitivity, fast response, wide test range, and large linear region. The sensor used in the present invention is a capacitive sensor from interdigitated electrodes, which has the advantages of capacitive sensors (high sensitivity, fast response, wide test range, large linear region), and the environment (such as temperature, humidity) has little influence on it.

[0093] (2) The IPMC has high driving performance, stable working state, and long working time in air. When a conventional IPMC is used as a driver, the existence of gaps between metal nanoparticles causes the loss of electrolyte (such as water) inside the polymer, which not only loses the electrolyte solution inside the membrane and reduces the working time of the IPMC in air, but also weakens the "weir effect" of the electrode and reduces the driving performance of the IPMC. In the present invention, a layer of polyvinylpyrrolidone-coated silver nanoparticles (PVP@AgNPS) (0.5μm - 5μm thick) is first coated on the surface of the IPMC electrode using the dip-coating technique, and then a layer of flexible polymethylvinylsiloxane (PMVS) (20μm - 100μm thick) is coated using a spin coater. The coating of this composite membrane not only solves the water loss problem of conventional IPMC and stabilizes the driving performance of IPMC, but also enhances the "weir effect" of the electrode and improves the driving performance of IPMC. It should be noted that the coating of pure PVP@AgNPS particles cannot completely prevent the leakage of the electrolyte solution. Especially in a high-frequency alternating electric field, water may also leak from the gaps between PVP@AgNPS particles. Pure PMVS cannot be stably coated on the surface of IPMC because the surface energy of the metal Pt electrode and the high polymer PMVS differ greatly, and PMVS may fall off from the surface of IPMC. However, the PVP on the surface of PVP@AgNPS particles has high compatibility with PMVS and can stably bond the PMVS film. Therefore, through the transition of PVP@AgNPS particles, PMVS can be fixed on the surface of IPMC for a long time.

[0094] (3) The drive system and the sensing system do not interfere with each other. When a conventional IPMC is working, a voltage of 0.5 - 5V is applied across the electrodes, which is much higher than the induced voltage (μV - mV) generated during the deformation of the IPMC. Therefore, the sensing signal is masked and difficult to filter, so it is difficult for a conventional IPMC to achieve the self-sensing function. The capacitive sensor in the present invention is an interdigital polydimethylsiloxane (PDMS) electrode, which can be effectively bonded to the surface of the PMVS without falling off. Due to the isolation of the PMVS, the drive signal and the sensing signal become two independent systems. Without signal filtering, the sensing signal can be separated, so the accuracy is high.

[0095] (4) The integration of drive and sensing of the IPMC is achieved. In the present invention, the IPMC moves under the excitation of an electric field, and the movement of the IPMC causes a change in the distance between the interdigital capacitors on its surface, thereby causing a change in capacitance. The change in capacitance can be collected at any time by a single-chip microcomputer to monitor the movement of the IPMC. With the assistance of accessories such as Bluetooth, real-time online detection of the IPMC displacement is realized, and further control of the IPMC movement is achieved.

Claims

1. A self-sensing IPMC artificial muscle, characterized in that: The self-sensing IPMC artificial muscle is composed of a driving layer, a transition layer, a sensing layer, an external driving signal module, and a sensor acquisition module, wherein the transition layer is located between the driving layer and the sensing layer, the driving layer is connected to the driving signal module, and the sensing layer is connected to the sensor acquisition module; The driving layer is an IPMC electric actuator prepared by chemical deposition using Nafion membrane as a base membrane and Pt nanoparticles as electrodes, wherein the base membrane thickness is 100-300 μm and the electrode thickness is 5-10 μm; The transition layer is composed of a PVP@AgNPS coating and a polyvinylsiloxane (PMVS) film, wherein the thickness of the PVP@AgNPS coating is 0.5-5 μm, and the thickness of the polyvinylsiloxane (PMVS) film is 20-100 μm; The sensing layer is composed of interdigital pattern electrodes, and the thickness of the sensing layer is 10-100 μm.

2. The self-sensing IPMC artificial muscle according to claim 1, wherein: The driving signal module is a low-voltage AC signal with a frequency of 0.1-10Hz, a driving voltage of 0.5-5V, and a waveform of a sine wave or a square wave; the sensor acquisition module is composed of a commercial single-chip microcomputer and Bluetooth, and can collect capacitance signals online in real time.

3. The preparation method of the self-sensing IPMC artificial muscle according to claim 1 or 2, characterized in that The following steps are involved: IPMC was prepared by encapsulating Pt particle electrode layers on both sides of Nafion substrate membrane using chemical plating process, and then a layer of dense polyvinyl pyrrolidone-coated silver nanoparticles (PVP@AgNPs) material was encapsulated on the surface of IPMC electrode using dip-coating technology as encapsulation electrode. Then, a layer of flexible PMVS polyolefin siloxane was coated on the surface of IPMC using a coater, and finally the interdigitated pattern electrode was encapsulated.

4. The preparation method of the self-sensing IPMC artificial muscle according to claim 3, characterized in that The following steps are involved: (1) Preparation of the driving layer: The IPMC electric actuator is prepared by encapsulating the Pt particle electrode layer on both sides of the Nafion substrate membrane using a chemical plating process; (2) Preparation of transition layer: A polyvinylpyrrolidone-encapsulated silver nanoparticle (PVP@AgNPS) coating was encapsulated on the surface of the IPMC electric actuator using a dip coating technique, and then a polyvinylsiloxane (PMVS) film was spin-coated on it using a spin coater; (3) Preparation of sensing layer: calibrate the interdigital pattern electrode and attach it to the PMVS film surface of the IPMC electric actuator obtained in step (2), bake it at 80°C for 30 minutes, and thermally bond the interdigital pattern electrode to the IPMC surface to obtain a self-sensing IPMC artificial muscle.

5. The preparation method of the self-sensing IPMC artificial muscle according to claim 4, characterized in that: The preparation method of the interdigital pattern electrode is as follows: (a) Electrode preparation: Weigh 5 g of conductive silicone rubber components A and B respectively and place them in a beaker, then add 7.5 g of silicone oil to each component, stir the two components A and B thoroughly to make them completely dissolved in the silicone oil, then mix the two components A and B, continue stirring, and store at low temperature; (b)Electrode coating: Cut a commercial polyethylene terephthalate film into a 6×6 mm rectangle by laser cutting. Lay the PVC film flat on a plastic petri dish to eliminate air bubbles. Stick the cut PET film on the PVC film, and then coat the prepared AB electrode on the rectangular part of the PET film. Peel off the PET film, lay the PVC film coated with the AB electrode flat on a plastic petri dish, and put it in an oven to dry; Take it out after drying, and use tweezers to remove the formed electrode film for storage; (c)Use a CO2 laser etching instrument with a maximum power of 60 kW, and control the output power at 55% at the computer end to etch interdigital pattern electrodes on the electrode film with a thickness of 10-100 μm.

6. The self-sensing IPMC artificial muscle according to claim 4, characterized in that: The sheet resistance of the IPMC actuator is 0.5-3.6 Ω / sq, and the sheet resistance of the IPMC actuator after PVP@AgNPs coating is in the range of 0.3-0.9 Ω / sq; the working displacement of the self-sensing IPMC artificial muscle is 0.5-9.3 mm, the deflection angle change range is 10-50°, the capacitance change range of the self-sensing IPMC artificial muscle is 11-145 pF, and the output force change range is 2.2-12.1 mN.

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