Piezoresistive / piezoelectric dual-mode sensing CD-ROM hydrogel driver and preparation method thereof

Abstract

The invention relates to a CD-ROM hydrogel driver integrated with a piezoresistive / piezoelectric dual-mode sensing function and a preparation method and application thereof. The preparation method of the CD-ROM hydrogel driver comprises the following steps: (1) preparing a PVA PNIPAM / PANI hydrogel driver; (2) preparing a P (VDF-TrFE) flexible piezoelectric film; and (3) preparation of the piezoresistive / piezoelectric dual-mode sensing double-layer light-driven hydrogel: taking the PVA PNIPAM / PANI hydrogel as a substrate, casting a PVA pre-polymerization solution, laying a P (VDF-TrFE) piezoelectric film, repeatedly freezing and thawing (low-temperature curing-room-temperature thawing), and soaking in a glutaraldehyde solution to complete chemical crosslinking, thereby obtaining the double-layer optical drive hydrogel driver. The CD-ROM hydrogel driver prepared by the invention has piezoresistive / piezoelectric dual-mode sensing performance and excellent light driving capability, and can be applied to the aspects of underwater intelligent robots, manipulator grabbing and the like.

Description

Technical Field

[0001] The invention belongs to the field of hydrogel driven sensing, and in particular relates to a preparation method and application of a light-driven hydrogel actuator for piezoresistive / piezoelectric dual-mode sensing. Background Art

[0002] Biological systems have evolved a variety of complex regulatory mechanisms to sense and respond to changes in the external environment. In the case of pine cones, due to the hygroscopic properties of individual cone scales, they can open when dry to release seeds and close when wet. Mimosa pudica is able to change the orientation of its leaves in response to mechanical stimulation (touch). Cephalopods (such as octopuses) exhibit a distributed sensory neuromotor control system with non-segmented arms that can sense their own movements (proprioception) and external tactile stimuli. The ability of these organisms to sense external stimuli and manage their movements to adapt to the environment has inspired the next paradigm of biological sensing and actuation devices. However, mimicking this biological somatosensory system to achieve active movement and perception functions requires the integration of sensors and actuators.

[0003] At present, there are several representative sensing technologies that are expected to be used in the development of new soft-actuated sensing integration, including piezoresistive, capacitive, piezoelectric, and triboelectric. Among the above sensing technologies, resistor-based sensors are the most common for detecting applied external stimuli and deformation of soft actuators. However, resistive sensors often have problems such as nonlinearity and hysteresis, and are easily affected by their surrounding environmental conditions (such as temperature, humidity, etc.). Capacitive sensors have high sensitivity and stable sensing signals, but their complex device structure and circuits limit their applications. Piezoelectric and triboelectric sensors have the advantage of being self-powered, but they are only suitable for dynamic mechanical sensing. However, complex signal conditioning electronics and limited stretchability limit their further application in soft actuators. Therefore, it will be challenging to develop an ideal hydrogel actuator with integrated driving / sensing technology to meet the requirements and balance various aspects, including compliant materials, sensory feedback, ease of manufacturing, and application scenarios. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a method for preparing a piezoresistive / piezoelectric dual-mode sensing optically driven hydrogel actuator, the method comprising the following steps:

[0005] (1) preparing an ammonium persulfate solution (APS) for use: adding ammonium persulfate to deionized water and stirring until completely dissolved, then adding deionized water to prepare an ammonium persulfate solution, and then precooling for use;

[0006] (2) preparing a hydrogel precursor solution: adding N,N'-methylenebisacrylamide (BIS), N-isopropylacrylamide (NIPAM), and 2-hydroxy-2-methyl-1-phenyl-1-propanone (1173) to a mixed solvent of dimethyl sulfoxide (DMSO) and deionized water and stirring to obtain a clear and transparent solution; then, adding ANI, HCl (37%), and PVA solution in an ice-water bath in sequence; after all components are completely dissolved, adding pre-cooled ammonium persulfate solution (APS) and stirring rapidly;

[0007] (3) Injection molding: Inject the prepared hydrogel precursor solution into the mold, and avoid generating bubbles during the injection process;

[0008] (4) Cross-linking: Place the mold after injection molding in an ice water bath under a UV lamp for light curing;

[0009] (5) Polymerization: The mold is then placed at low temperature to polymerize aniline. After the reaction is complete, the mold is removed and rinsed repeatedly with deionized water to obtain a light-driven / piezoresistive sensing (PVA) PNIPAM / PANI hydrogel actuator.

[0010] (6) Preparation of P(VDF-TrFE) flexible piezoelectric film: P(VDF-TrFE) powder was dissolved in N,N-dimethylformamide (DMF), and then heated and stirred until completely dissolved to obtain a colorless and transparent uniform solution. The uniform solution was then dripped onto a glass mold, scraped flat with a scraper, and placed in an oven to dry into a thin film. The film was then annealed, cooled to room temperature, and demolded. The film was then placed in a silicone oil bath and polarized under an electric field. Finally, the film was washed several times to remove the residual silicone oil on the surface of the film, thereby obtaining the P(VDF-TrFE) piezoelectric film.

[0011] (7) Preparation of piezoresistive / piezoelectric dual-mode double-layer light-driven hydrogel: PVA is added to deionized water, heated in a water bath and stirred until completely dissolved to obtain a PVA solution. The (PVA)PNIPAM / PANI hydrogel obtained in step (5) is made into a mold with a silicone pad, tape and a glass slide. The PVA solution is cast on the mold and cooled and solidified to form a gel. After the PVA layer is formed, the P(VDF-TrFE) piezoelectric film prepared in step (6) is laid on it. Then, the PVA solution is cast again and the cooling and solidification-room temperature thawing process is repeated. The freeze-thaw process is repeated 3 times to obtain a double-layer hydrogel. The double-layer hydrogel is then placed in a glutaraldehyde solution for immersion to complete chemical crosslinking. After being taken out, it is washed with an excess of deionized water to obtain a piezoresistive / piezoelectric dual-mode sensing light-driven hydrogel actuator.

[0012] Furthermore, the concentration of the ammonium persulfate solution (APS) in step (1) is 1.5-2.5 mol / L, and the precooling temperature is 0-4°C.

[0013] Furthermore, in step (2), the DMSO accounts for 40% to 80% of the total volume.

[0014] Furthermore, the mass concentration of the PVA solution in step (2) is 2-10%.

[0015] Furthermore, in the step (4), the distance between the ultraviolet lamp and the mold is 12 to 18 cm, the wavelength of the ultraviolet lamp is 350 to 380 nm, the power is 250 W, and the ultraviolet lamp irradiation cross-linking time is 6 to 8 minutes.

[0016] Furthermore, in step (7), the concentration of the glutaraldehyde solution is 0.8-1.2 wt %, and the soaking and cross-linking time is 9-12 h.

[0017] The present invention also provides a piezoresistive / piezoelectric dual-mode sensing optically driven hydrogel actuator prepared according to the above preparation method.

[0018] The present invention also provides an application of the above-mentioned light-driven hydrogel actuator, where the light-driven hydrogel actuator is assembled on an octopus tentacle to grasp objects, and while achieving rapid grasping under light, piezoresistance and piezoelectric signals are fed back in real time.

[0019] The present invention has the following advantages:

[0020] 1. Due to the efficient photothermal effect of polyaniline and the high responsiveness of the open-pore structure, the (PVA)PNIPAM / PANI composite hydrogel exhibits omnidirectional light-driven capabilities, bending to more than 90° within 4 seconds under ultraviolet light irradiation, and the recovery time is shortened to less than 10 seconds.

[0021] 2. The dual-mode sensor can collect information on bending angle, bending rate and bending direction during the bending process and simulate the actual bending process, demonstrating excellent in vitro sensing capabilities.

[0022] 3. Since sensing and actuation are integrated into a single material, motion feedback can be obtained through real-time resistance changes when the hydrogel bends under photothermal actuation, thereby realizing the dual functions of remote-controlled actuation and self-sensing of the hydrogel system. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a diagram of the underwater driving and recovery process and angle change of the hydrogel under near-infrared light irradiation.

[0024] Figure 2 The bending deformation of the hydrogel in water under near-infrared light has synchronously fed back the bending angle and real-time self-sensing resistance change diagram.

[0025] Figure 3 Signal diagram for piezoelectric sensing to dynamically identify the bending of hydrogel in different directions.

[0026] Figure 4 The hydrogel is assembled on the octopus arm and realizes the process of grasping objects and synchronously feeding back piezoresistive / piezoelectric signals.

[0027] Figure 5 It is the real-time sensing signal of the optical drive grabbing process. DETAILED DESCRIPTION

[0028] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0029] Example 1

[0030] (1) Preparation steps of optically driven hydrogel actuator with piezoresistive / piezoelectric dual-mode sensing:

[0031] a) Prepare ammonium persulfate solution (APS) for use: add 4.564 g of ammonium persulfate into a certain amount of deionized water and stir until completely dissolved, then continue to add deionized water to make the solution volume to 10 mL, to prepare an ammonium persulfate solution with a concentration of 2 mol / L, and then place it in the upper layer of a refrigerator (4°C) for precooling for use.

[0032] b) Preparation of hydrogel precursor solution: 20 mg N,N'-methylenebisacrylamide (BIS), 1 g N-isopropylacrylamide (NIPAM), and 25 μL 2-hydroxy-2-methyl-1-phenyl-1-propanone (1173) were added to 3 mL of dimethyl sulfoxide (DMSO) / deionized water mixed solvent and stirred evenly to obtain a clear and transparent solution. Subsequently, 138 μL ANI, 0.42 mL HCl (37%), and 1 mL PVA (10%) were added in an ice water bath. After all components were completely dissolved, 0.5 mL of pre-cooled APS solution was added and stirred rapidly for 1 min.

[0033] c) Injection molding: Inject the prepared hydrogel precursor solution into a mold, which is composed of two glass slides (60 mm × 25 mm) sandwiching a silicone gasket with a hollow area of ​​40 mm × 10 mm in the middle. The thickness of the silicone gasket is controllable and is 1.5 mm thick unless otherwise specified. Carefully inject the hydrogel precursor solution into the above mold to avoid generating bubbles during the injection process;

[0034] d) Cross-linking: The mold after injection molding was placed in an ice water bath 15 cm below a UV lamp (λ=365 nm, 250 W) for 6 min. After curing, the mold was demolded to obtain the (PVA)PNIPAM composite hydrogel.

[0035] e) Polymerization: The mold was then placed at 4°C to polymerize aniline, and after waiting for 72 hours, it was taken out and demolded, and repeatedly rinsed with deionized water to obtain a light-driven / piezoresistive sensing (PVA) PNIPAM / PANI hydrogel actuator.

[0036] f) Preparation of P(VDF-TrFE) flexible piezoelectric film: Dissolve P(VDF-TrFE) powder in N,N-dimethylformamide (DMF) at a mass ratio of 1:20, and then place the mixed solution in a 60°C water bath and heat and stir for 3 hours until it is completely dissolved to obtain a colorless, transparent, uniform solution. The solution is then dripped onto a glass mold, scraped flat with a scraper, and placed in an 80°C oven to dry for 30 minutes to form a film. Annealing treatment is then performed at 120°C for 2 hours to increase the crystallinity of the film, and then demolding is performed after cooling to room temperature. The annealed film is placed in a silicone oil bath, polarized under a 1kV high voltage electric field for 2 hours, and then taken out. Finally, it is washed several times to remove the residual silicone oil on the surface of the film to obtain the P(VDF-TrFE) piezoelectric film;

[0037] g) Preparation of piezoresistive / piezoelectric dual-mode double-layer light-driven hydrogel: 10g PVA was added to 90mL deionized water and stirred at 95°C for 5h until completely dissolved to obtain a 10% PVA solution. The (PVA) PNIPAM / PANI hydrogel obtained in step (5) was made into a mold with a silicone pad, tape and glass slide, and the 10% PVA solution was cast on the mold, and cooled at -20°C for 30min to solidify to form a gel. After the PVA layer was formed, the P(VDF-TrFE) piezoelectric film prepared in step (6) was placed on it, and then 10% PVA solution was cast again and low-temperature solidified for 30min. After the PVA layer was solidified, it was taken out and thawed at room temperature for 30min, and then continued to be placed in a refrigerator for low-temperature solidification. The freeze-thaw process was repeated 3 times to obtain a double-layer hydrogel. Subsequently, the double-layer hydrogel was placed in a 1wt% glutaraldehyde solution and soaked for 10h to complete chemical crosslinking. After being taken out, it was washed and soaked with excess deionized water to obtain the final piezoresistive / piezoelectric dual-mode sensing light-driven hydrogel actuator.

[0038] (2) Driving performance test: When near-infrared light is irradiated on the hydrogel strip at any angle, the hydrogel bends in the direction of the incident light and can accurately track the light source. When the light source is turned on, the hydrogel quickly bends to more than 90° within 4 seconds. When the light source output is maintained, the hydrogel bends in the direction of the light source. When the light source is turned off, the hydrogel quickly returns to its original undeformed structure within 10 seconds. Figure 1 The underwater optical drive-recovery process of the hydrogel is shown, which shows that the composite hydrogel has excellent optical drive performance.

[0039] (3) Sensing performance test: In strain detection, the sensing modes of the piezoresistive layer and the piezoelectric layer have their own shortcomings. The piezoresistive sensing mode has good static sensing characteristics and can sense the specific bending strain size, but it cannot detect the bending direction. Figure 2 This is the real-time piezoresistive layer signal feedback of the hydrogel during the optical drive process. During the underwater light-driven process, the hydrogel bends due to the local contraction of the illuminated part. At this time, the bent part of the hydrogel is in a compressed state, causing the PANI network to contract and enhance conductivity. During the underwater self-sensing drive process, the resistance decreases as the bending angle increases. Figure 3 The bending signal feedback of the hydrogel piezoelectric layer is defined here as a positive bending angle to the left and a negative bending angle to the right. During bending recovery and reverse bending, the voltage output by the piezoelectric sensor is negative. Since the piezoelectric peak value is only related to the strain rate at the instant of deformation, the piezoelectric output signal in the two strain processes cannot distinguish the bending direction. Dual-mode sensing is needed to solve this problem.

[0040] (4) Dual-mode sensing: During the bending strain detection process, piezoresistive and piezoelectric sensing modes are used simultaneously. Different sensing modes complement each other to obtain more comprehensive bending strain information. In actual testing, the dual-mode sensor can simultaneously sense the bending angle, strain rate and bending direction of the sample. Figure 4 The real-time feedback signal of dual-mode sensing is demonstrated: when the piezoelectric signal is positive, the resistance increases and the surface bends to the left. When the piezoelectric signal is negative, the resistance increases and the surface bends to the right. When the piezoelectric signal is negative, the resistance decreases and the surface bends back to the right.

[0041] Example 2

[0042] In order to further demonstrate the real-time signal feedback during the autonomous driving process, we assembled the hydrogel on the octopus model arm as a soft proprioceptive arm to imitate the movement process of the octopus grabbing objects in the water. The octopus arm starts from a straight non-moving state, begins to bend under the irradiation of near-infrared light, and wraps around the cylinder. After a period of time, the light is turned off, and the octopus arm lets go of the cylinder and returns to its original state. During this process, we collect its resistance signal and voltage signal in real time. When the near-infrared light irradiates the octopus arm, the hydrogel begins to bend, and a positive voltage pulse is generated at this time, and the relative resistance decreases at the same time; when the resistance tends to be stable, it indicates that the octopus arm has grasped the object; when the light is turned off, a negative voltage signal is generated at this time, and the resistance increases, and the surface octopus arm lets go of the object and begins to recover. After a period of time, the resistance begins to stabilize, and the bending of the surface hydrogel is basically restored. Figure 5 It is the real-time sensing signal of the optical drive grabbing process.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a piezoresistive / piezoelectric dual-mode sensing optically driven hydrogel actuator, comprising the following steps: (1) preparing an ammonium persulfate solution (APS) for use: adding ammonium persulfate to deionized water and stirring until completely dissolved, then adding deionized water to prepare an ammonium persulfate solution, and then precooling for use; (2) preparing a hydrogel precursor solution: adding N,N'-methylenebisacrylamide (BIS), N-isopropylacrylamide (NIPAM), and 2-hydroxy-2-methyl-1-phenyl-1-propanone (1173) to a mixed solvent of dimethyl sulfoxide (DMSO) and deionized water and stirring to obtain a clear and transparent solution; then, adding ANI, HCl (37%), and PVA solution in an ice-water bath in sequence; after all components are completely dissolved, adding pre-cooled ammonium persulfate solution (APS) and stirring rapidly; (3) Injection molding: Inject the prepared hydrogel precursor solution into the mold, and avoid generating bubbles during the injection process; (4) Cross-linking: Place the mold after injection molding in an ice water bath under a UV lamp for light curing; (5) Polymerization: The mold is then placed at low temperature to polymerize aniline. After the reaction is complete, the mold is removed and rinsed repeatedly with deionized water to obtain a light-driven / piezoresistive sensing (PVA) PNIPAM / PANI hydrogel actuator. (6) Preparation of P(VDF-TrFE) flexible piezoelectric film: P(VDF-TrFE) powder was dissolved in N,N-dimethylformamide (DMF), and then heated and stirred until completely dissolved to obtain a colorless and transparent uniform solution. The uniform solution was then dripped onto a glass mold, scraped flat with a scraper, and placed in an oven to dry into a thin film. The film was then annealed, cooled to room temperature, and demolded. The film was then placed in a silicone oil bath and polarized under an electric field. Finally, the film was washed several times to remove the residual silicone oil on the surface of the film, thereby obtaining the P(VDF-TrFE) piezoelectric film. (7) Preparation of piezoresistive / piezoelectric dual-mode double-layer light-driven hydrogel: PVA is added to deionized water, heated in a water bath and stirred until completely dissolved to obtain a PVA solution. The (PVA)PNIPAM / PANI hydrogel obtained in step (5) is made into a mold with a silicone pad, tape and a glass slide. The PVA solution is cast on the mold and cooled and solidified to form a gel. After the PVA layer is formed, the P(VDF-TrFE) piezoelectric film prepared in step (6) is laid on it. Then, the PVA solution is cast again and the cooling and solidification-room temperature thawing process is repeated. The freeze-thaw process is repeated 3 times to obtain a double-layer hydrogel. The double-layer hydrogel is then placed in a glutaraldehyde solution for immersion to complete chemical crosslinking. After being taken out, it is washed with an excess of deionized water to obtain a piezoresistive / piezoelectric dual-mode sensing light-driven hydrogel actuator.

2. The method for preparing a piezoresistive / piezoelectric dual-mode sensing optically driven hydrogel actuator according to claim 1, characterized in that: The concentration of the ammonium persulfate solution (APS) in step (1) is 1.5-2.5 mol / L, and the precooling temperature is 0-4°C.

3. The method for preparing a piezoresistive / piezoelectric dual-mode sensing optically driven hydrogel actuator according to claim 1, characterized in that: In step (2), the DMSO accounts for 40% to 80% of the total volume.

4. The method for preparing a piezoresistive / piezoelectric dual-mode sensing optically driven hydrogel actuator according to claim 1, characterized in that: The mass concentration of the PVA solution in step (2) is 2-10%.

5. The method for preparing a piezoresistive / piezoelectric dual-mode sensing optically driven hydrogel actuator according to claim 1, characterized in that: In the step (4), the distance between the ultraviolet lamp and the mold is 12 to 18 cm, the wavelength of the ultraviolet lamp is 350 to 380 nm, the power is 250 W, and the ultraviolet lamp irradiation cross-linking time is 6 to 8 minutes.

6. The method for preparing a piezoresistive / piezoelectric dual-mode sensing optically driven hydrogel actuator according to claim 1, characterized in that: The concentration of the glutaraldehyde solution in step (7) is 0.8-1.2 wt %, and the soaking and cross-linking time is 9-12 h.

7. A piezoresistive / piezoelectric dual-mode sensing optically driven hydrogel actuator prepared by the preparation method as claimed in claims 1 to 7.

8. An application of the optically driven hydrogel actuator as claimed in claim 1, characterized in that: The light-driven hydrogel actuator is assembled on the octopus tentacles to grasp objects, and can achieve rapid grasping under light while providing real-time feedback of piezoresistance and piezoelectric signals.

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