A non-contact sensing-actuating composite material and a preparation method thereof

Abstract

The application discloses a kind of non-contact sensing-actuating composite material and its preparation method, the method comprises: the shape memory fiber film is pre-stretched to produce deformation after cooling and is fixed to obtain sensing-actuating layer;Electrode is prepared on the partial area of the upper surface of sensing-actuating layer;Sensing-actuating layer is laminated on the polydimethylsiloxane film that is not completely cured, and it is completely cured by standing, and the face of sensing-actuating layer preparation electrode faces polydimethylsiloxane film;Silver nanowire dispersion liquid is coated on the face of sensing-actuating layer not prepared electrode, and dried.The composite material of the application has nanoscale multilayer network structure, based on "dielectric polarization-electric heating conversion-thermal response actuation" triple effect, self-awareness and actuating are fused, complete and accurate logical relationship is established with three-dimensional movement and triggers material to carry out flexible actuating, realizes non-contact "sensing-actuating" integration.

Description

Technical Field

[0001] This invention relates to the field of sensing and actuation materials technology, and in particular to a non-contact sensing-actuation composite material and its preparation method. Background Technology

[0002] With the development of artificial intelligence, soft actuators, in addition to simply receiving instructions to undergo mechanical deformation, also need to more intelligently perceive external environmental information and make corresponding action feedback, mimicking the human sensory-motor system [Nat.Rev.Neurosci.201112(3):139-153]. Therefore, the design of smart materials needs to integrate sensing and actuation characteristics. Among them, the sensing methods are divided into two types: proprioceptive perception of its own deformation and environmental perception of external information [Science 2015,347(6228):12616891].

[0003] Research on materials sensing their own deformation and controlling it to form a closed-loop control has been reported. Hao et al. designed an electrothermal actuator based on laser-induced graphene (LIG) and sensed its deformation state through the resistance change of LIG, but the required bending angle and number of cycles could only be achieved when the driving voltage was 20V [ACS Appl. Mater. Interfaces 2022, 14, 41283-41295]. Wang proposed a light-driven miniature flexible robot with proprioception. The robot is composed of a multilayer structure of conductive graphite-carbon nanotube composite material, ferroelectric polyvinylidene fluoride (PVDF), photothermal polydopamine (PDG), and reduced graphene oxide. PVDF and PDG, which have opposite coefficients of thermal expansion, constitute a bilayer actuator. Temperature changes and driving strain are fed back through the pyroelectricity of PVDF and the piezoresistive properties of the graphite-carbon nanotube circuit, respectively. However, crosstalk can easily occur between the various sensing signals [Adv.Mater.2020,32,2000351]. Lo et al. designed a self-sensing actuated soft material composed of thermally responsive hydrogel poly(n-isopropylacrylamide) (PNIPAAm) and light-absorbing conductive polymer polypyrrole (PPy). This design enables the material to have photo / thermal responsiveness and piezoresistive feedback, thereby realizing remote photo-triggered actuation and local strain sensing. However, its sensing range is limited, and significant resistance changes can only be collected under tensile strain >200% [Materials Today 2021, 11, 35-43].

[0004] Furthermore, some materials can sense the external environment and thus control its actuation. Contact sensing is relatively mature, with sensing mechanisms including piezoelectric, piezoresistive, piezoresistive, and triboelectric [Adv. Funct. Mater. 2024, 2401311]. Zhang et al. reported a single homogeneous material based on silver-polymer to simultaneously realize the sensing-actuation function of pneumatic artificial muscles. This material senses and responds to contact mechanical signals based on capacitive and piezoresistive mechanisms and can perceive its own deformation [Adv. Mater. 2023, 35, 2207916]. However, the demand for information exchange between humans and machines or virtual spaces is rapidly increasing. Contact sensing cannot fully acquire environmental information and inevitably causes mechanical wear and the spread of bacteria / viruses during the sensing process [Adv. Mater. 2021, 33, 2100218]. Therefore, it is necessary to focus on the integration of non-contact sensing and actuation. Based on the differences in the physical fields and detection mechanisms used, non-contact sensors can be broadly classified into various types such as electric field, magnetic field, humidity field, and optical field [Sci.Adv.2022,8(43)]. For example, Ha et al. prepared a shape memory polymer composite film embedded with magnetic neodymium iron boron microparticles to integrate photothermal and magnetic actuation into a paper-folding actuator, in which the laminated magnetic field sensor can guide self-assembly by detecting the magnetic field. However, the simple physical assembly of the actuator and sensing elements is prone to problems such as poor adhesion and mismatch of mechanical properties of different materials, and the whole system requires different energies for driving and sensing, making it difficult to miniaturize [Adv.Mater.2021,33,2008751]. Xue et al. proposed a multi-stimulus response actuator (MSRA) with an asymmetric expansion structure and used screen printing to integrate carbon black / highly elastic transparent adhesive cement (CB / HETAC) conductive ink with arbitrary patterns onto the soft actuator. MSRA not only bends in the reverse direction under near-infrared light and humidity, but also exhibits different bending angles and corresponding resistance feedback under a range of near-infrared light powers, enabling it to recognize its own deformation [ACS Appl. Polym. Mater. 2023, 5, 4525-4535]. In non-contact sensing and actuation, most of the aforementioned devices sense environmental information for specific scenarios, or are primarily driven by light fields, magnetic fields, etc., without logically sensing external stimuli.

[0005] The current problems in the design of sensing-actuation integrated materials include: (1) When smart materials sense external environmental information, they mostly remain at the 2D skin surface contact or pressure sensing, resulting in unavoidable contact damage and power consumption, as well as incomplete transmission of external environmental information; (2) When smart materials sense external non-contact stimuli, their non-contact information is mostly special environment, such as magnetic field, humidity field, light field, etc., and the sensing function is single and cannot realize logical perception of the direction and speed of external objects; (3) In the existing electric / electrothermal driven flexible actuation materials, the driving voltage is large, such as tens or even hundreds of volts, which is not conducive to safe interaction and energy saving and emission reduction. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a non-contact sensing-actuation composite material and its preparation method. The composite material provided by this invention possesses a nanoscale multilayer network structure, and is a smart material integrating autonomous sensing and actuation based on the triple effect of "dielectric polarization-electrothermal conversion-thermal response actuation." The composite material of this invention can logically perceive the three-dimensional motion of non-contact objects in the environment based on the electrostatic field and its polarization effect on dielectric materials, establish a complete and precise logical relationship with the three-dimensional motion, and trigger flexible actuation of the material, thus achieving non-contact "sensing-actuation" integration.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] On one hand, the present invention provides a method for preparing a non-contact sensing-actuation composite material, comprising the following steps:

[0009] S1. The shape memory fiber membrane is pre-stretched to produce deformation and then cooled and fixed to obtain the sensing-actuation layer; the shape memory fiber membrane is a shape memory polyurethane fiber membrane doped with dielectric particles.

[0010] S2. An electrode is fabricated in a portion of the upper surface of the sensing-actuation layer;

[0011] S3. The sensing-actuation layer is stacked on the incompletely cured polydimethylsiloxane (PDMS) film, and left to stand to allow the PDMS film to fully cure; the side of the sensing-actuation layer with electrodes is facing the incompletely cured PDMS film.

[0012] S4. A silver nanowire dispersion is coated onto the surface of the sensing-actuation layer where no electrodes are prepared, and after drying, the non-contact sensing-actuation composite material is obtained.

[0013] In some specific embodiments, the thickness of the sensing-actuation layer is 40–90 μm; the thickness of the electrode is 30–80 μm; the thickness of the polydimethylsiloxane (PDMS) film after complete curing is 160–1750 μm; and the thickness of the silver nanowire dispersion coating after drying is 0.89–5.36 μm. In the technical solution of the present invention, the sensing-actuation layer with a thickness of 40–90 μm can drive the bending actuation of the electrode, polydimethylsiloxane (PDMS) film, and silver nanowire layer within the above thickness range.

[0014] In a preferred embodiment, in step S1, the soft segments in the shape memory polyurethane are selected from any one of polycaprolactone polyols; the polycaprolactone polyol is polycaprolactone diol (PCL-diol) or polycaprolactone triol (PCL-triol); the hard segments in the shape memory polyurethane are the product of the polycondensation reaction of diisocyanate and 1,4-butanediol, and the diisocyanate is selected from any one of diphenylmethyl diisocyanate, hexamethylene diisocyanate, and isoflurone diisocyanate;

[0015] Preferably, the method for preparing the shape memory polyurethane includes the following steps:

[0016] (1) Prepolymerize polycaprolactone polyol and diisocyanate;

[0017] (2) The reaction continued after the addition of 1,4-butanediol;

[0018] Preferably, the mass ratio of the soft segment to the hard segment is 70-80:20-30, and more preferably 72:28;

[0019] Preferably, the molar ratio of the total number of hydroxyl groups in the 1,4-butanediol and polycaprolactone polyol to the isocyanate in the diisocyanate is 1:1 to 1.2, more preferably 1:1.05;

[0020] Preferably, the molecular weight of the polycaprolactone polyol is 3000-5000 g / mol;

[0021] Preferably, in step (1), the reaction temperature of the prepolymerization is 80-100°C, and the reaction time of the prepolymerization is 2-3 hours;

[0022] Preferably, in step (2), the temperature of the continued reaction is 80-100°C, and the time of the continued reaction is 0.5-5 min; in the technical solution of the present invention, a large amount of heat is released during the continued reaction process;

[0023] Preferably, in steps (1) and (2), the prepolymerization and continued reaction are carried out under stirring conditions;

[0024] In some specific embodiments, step (2) before adding 1,4-butanediol further includes a vacuum degassing operation; step (2) further includes a drying post-treatment, wherein the drying is performed at 80-100°C for 8-12 hours;

[0025] In the technical solution of this invention, 1,4-butanediol is used as a chain extender.

[0026] In a preferred embodiment, in step S1, the dielectric particles are boron nitride nanosheets;

[0027] Preferably, the boron nitride nanosheets are prepared by liquid-phase exfoliation.

[0028] Preferably, the liquid phase stripping method includes the following steps:

[0029] Boron nitride was dispersed in a solvent and then exfoliated by ultrasonic oscillation to obtain the boron nitride nanosheets.

[0030] In some specific embodiments, the solvent is selected from any one of an aqueous solution of isopropanol, N-methylpyrrolidone, and N,N-dimethylformamide; wherein, in the aqueous solution of isopropanol, the weight ratio of water to isopropanol is 1:1.

[0031] Preferably, the ultrasonic oscillation time is 6–12 hours;

[0032] In some specific embodiments, the ultrasonic oscillation includes post-treatment such as centrifugation to collect the supernatant and centrifugation to collect boron nitride nanosheet precipitate from the supernatant.

[0033] In a preferred embodiment, in step S1, the shape memory polyurethane fiber membrane is prepared by electrospinning from a precursor solution containing boron nitride nanosheets and shape memory polyurethane.

[0034] Preferably, the solid content of the precursor liquid containing boron nitride nanosheets and shape memory polyurethane is 5-15 wt%.

[0035] Preferably, in the precursor solution containing boron nitride nanosheets and shape memory polyurethane, the mass of the boron nitride nanosheets is 3% to 8% of the mass of the polyurethane;

[0036] Preferably, the solvent of the precursor solution is selected from any one of hexafluoroisopropanol, N,N-dimethylformamide, tetrahydrofuran, dichloromethane, and chloroform;

[0037] In some specific embodiments, the preparation method of the precursor liquid containing boron nitride nanosheets and shape memory polyurethane includes the following steps: dissolving shape memory polyurethane in a solvent, adding boron nitride nanosheets and dispersing them evenly; wherein the shape memory polyurethane is dissolved in the solvent under heating conditions, and the heating temperature is 45-60°C.

[0038] Preferably, the ambient temperature for electrospinning is 45–60°C;

[0039] Preferably, in the electrospinning process, the distance between the nozzle and the collector is 10-20 cm;

[0040] Preferably, the collector is a rotary collector, and the rotational speed of the rotary collector is 1000-5000 rpm;

[0041] In a preferred embodiment, the pre-stretching produces a deformation to a strain of 100-300%;

[0042] Preferably, the pre-stretching is performed at 35–80°C.

[0043] Preferably, the cooling and fixing temperature is 0–15°C.

[0044] In the technical solution of the present invention, in step S2, the material of the electrode layer is not particularly limited, and any metal with good conductivity is acceptable, such as copper, silver, etc.

[0045] In a preferred embodiment, step S3, the method for preparing the incompletely cured polydimethylsiloxane (PDMS) film includes the following steps:

[0046] After mixing polydimethylsiloxane with a curing agent, pre-curing is carried out at 80–120°C for 3–5 minutes.

[0047] In the technical solution of the present invention, the curing agent is a conventional curing agent used for curing polydimethylsiloxane;

[0048] Preferably, in step S3, the mass ratio of polydimethylsiloxane to curing agent is 10-15:1;

[0049] Preferably, in step S3, the settling time is 8 to 24 hours;

[0050] In the technical solution of the present invention, during the static process, the incompletely cured polydimethylsiloxane can slightly penetrate the contact surface of the sensing-actuation layer through diffusion.

[0051] In a preferred embodiment, in step S4, the silver nanowire dispersion comprises silver nanowires and a dispersant; the diameter of the silver nanowires is 30–90 nm and the length is 2–20 μm; the dispersant is selected from at least one of water, isopropanol, ethanol, cyclohexane, and glycerol; and the concentration of the silver nanowire dispersion is 0.1–100 mg / mL.

[0052] In the technical solution of the present invention, when the coating amount of silver nanowire dispersion is different, it has different resistance after drying and generates different amounts of heat when energized. By controlling its resistance, the optimal thermal response drive of the sensing-actuation layer can be achieved.

[0053] Preferably, in step S4, the drying is air drying at room temperature;

[0054] In some specific embodiments, the coating process further includes a plasma treatment step on the sensor-actuator layer and the sensor-actuator layer in the polydimethylsiloxane (PDMS) film after they have been left to stand. After the plasma treatment, the silver nanowire dispersion can be spread evenly on the sensor-actuator layer.

[0055] In another aspect, the present invention provides a non-contact sensing-actuation composite material obtained by the above preparation method.

[0056] In the technical solution of the present invention, the non-contact sensing-actuation composite material sequentially comprises a silver nanowire layer, a sensing-actuation layer, an electrode, and a polydimethylsiloxane underlayer; the silver nanowire layer is formed by drying a silver nanowire dispersion; by connecting the two ends of the silver nanowire layer in the non-contact sensing-actuation composite material with wires, the composite material can realize actuation behavior driven by electrothermal energy; by connecting the electrode with wires, the composite material can realize non-contact "dielectric polarization-electrothermal conversion-thermal response actuation" integration.

[0057] The above technical solution has the following advantages or beneficial effects:

[0058] This invention provides a non-contact sensing-actuation composite material based on dielectric and shape memory polymers. The composite material uses a thermally responsive shape memory polymer network as a substrate, coupled with a dielectric / thermal conductive network formed by dielectric particles such as boron nitride (BNNS) and a silver nanowire electrothermal conversion network. Based on the control of the dielectric constant, the material can achieve logical sensing of the motion of external objects (including direction, speed, distance, etc.) through a conductive-dielectric heterostructure. A precise logical relationship is established between the positive / negative, frequency, and amplitude of the sensing signal and the three-dimensional motion of the object, with a sensing distance of up to 20 cm. Furthermore, the composite material applies the output voltage of the non-contact sensing signal to a silver nanowire layer with an electrothermal effect. By controlling the resistance of the silver nanowire layer, the shape memory polymer is driven to generate action feedback. This thermally responsive actuation time is less than 1 second, and its shape memory recovery rate is greater than 95%.

[0059] The composite material provided by this invention can achieve flexible actuation by coupling the triple effects of "dielectric polarization-electrothermal conversion-thermal response actuation" through the logical perception of the three-dimensional motion of a non-contact external object. This integrates "sensing-actuation," specifically by using the dielectric properties of the material to achieve non-contact sensing based on electrostatic field theory and outputting a logical electrical signal; and by using the signal and energy conversion of the electrothermal network to drive the thermally responsive polymer network to achieve flexible actuation, which is compatible with the sensing function. The preparation method and process of this non-contact "sensing-actuation" polymer composite material are simple, easy to implement in industrialization, and have wide applicability.

[0060] Compared with the prior art, the present invention has the following advantages:

[0061] (1) In traditional smart materials, the sensing and actuation functions are independent and separate, and sensing and actuation require different energies. In contrast, this invention integrates the sensing layer and the actuation layer in the same material at the nanoscale, which has a simple structure and can realize sensing and actuation using a single energy conversion.

[0062] (2) The preparation process of the present invention is simple, and the resulting composite material has both actuation capability and sensing stability. Traditional flexible actuation materials not only require voltage driving, but also have harsh driving conditions and require high driving voltage. The composite material provided by the present invention has a driving voltage as low as 2V and a response speed of less than 1s, which reduces the threshold for use.

[0063] (3) Most current non-contact sensing materials require special environments for excitation, such as magnetic fields, humidity fields, light fields, etc., and their sensing functions are limited and cannot realize the logical perception of the non-contact motion of ordinary objects in daily scenes. The non-contact sensing mechanism in this invention utilizes the polarization effect of electrostatic field on dielectric materials, without special scene restrictions, thus expanding the scope of application. Attached Figure Description

[0064] Figure 1 This is a scanning electron microscope (SEM) image of the shape memory polyurethane fiber membrane in Embodiment 1 of the present invention.

[0065] Figure 2 The image shows the differential scanning calorimetry (DSC) results of shape memory polyurethane fiber membranes with different BNNS doping amounts in Example 1 of this invention.

[0066] Figure 3 The graph shows the dielectric constant test results of shape memory polyurethane fiber films with different BNNS doping amounts in Example 1 of the present invention.

[0067] Figure 4 This is a non-contact sensing signal diagram of shape memory polyurethane fiber membranes with different BNNS doping amounts in Embodiment 1 of the present invention.

[0068] Figure 5 This is a diagram showing the thermal response bending actuation process of the BNNS / SMPUFs-PDMS composite membrane in Embodiment 2 of the present invention.

[0069] Figure 6 The image shows the time-electrothermal temperature curves of AgNWs layers with different resistances at 2V in the AgNWs-BNNS / SMPUFs-PDMS film composite material of Example 2 of the present invention.

[0070] Figure 7 This is a bending actuation diagram of the electrothermal response of the film composite material AgNWs-BNNS / SMPUFs-PDMS in Example 2 of the present invention.

[0071] Figure 8 The results show the test results of the film composite material AgNWs-BNNS / SMPUFs-PDMS in Example 2 of this invention on the induced electromotive force generated by the approach-away motion of a charged object.

[0072] Figure 9 This is a schematic diagram showing the connection of the film composite material AgNWs-BNNS / SMPUFs-PDMS in Embodiment 2 of the present invention using conductive copper wires.

[0073] Figure 10 This is a non-contact sensing-actuation fusion roadmap for the film composite material AgNWs-BNNS / SMPUFs-PDMS in Example 3 of the present invention. Detailed Implementation

[0074] The following embodiments are merely some, not all, of the embodiments of the present invention. Therefore, the detailed descriptions of the embodiments provided below are not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0075] In this invention, unless otherwise specified, all equipment and raw materials are commercially available or commonly used in the industry. The methods described in the following embodiments are conventional methods in the art, unless otherwise specified.

[0076] In the following embodiments:

[0077] The molecular weight M of polycaprolactone diol (PCL-diol) n =4000g·mol -1 ;

[0078] The molecular weight of diphenylmethyl diisocyanate (MDI) is M n =250.26 g·mol -1 ;

[0079] The molecular weight of 1,4-butanediol (BDO) is M. n = 90.12 g·mol -1 ;

[0080] The boron nitride nanosheets have a size of 200 nm.

[0081] Example 1: Preparation of shape memory polyurethane fiber membranes (BNNS / SMPUFs)

[0082] (1) Synthetic shape memory polyurethane (SMPU)

[0083] Using PCL-diol as the soft segment and MDI-BDO as the hard segment, an SMPU with a soft-to-hard segment mass ratio of 72 / 28 was synthesized, wherein the molar ratio of hydroxyl to isocyanate was 1:1.05. The specific synthetic route is as follows:

[0084] PCL-diol and BDO were vacuum dried for 2 hours; 25g of PCL-diol and 7.65g of MDI were placed in a three-necked flask and stirred at 85°C for 2 hours for prepolymerization; the bubbles were removed under vacuum, and then 2.06g of BDO was added dropwise for chain extension. When a large amount of heat was released, the mixture was quickly poured into a polytetrafluoroethylene plate mold and placed in an oven at 80°C for 12 hours to obtain shape memory polyurethane (SMPU).

[0085] (2) Preparation of boron nitride nanosheets (BNNS) by liquid phase exfoliation

[0086] 3.5 g of BN was dispersed in 200 mL of a mixed solvent of deionized water and isopropanol (weight ratio of deionized water to isopropanol was 1:1) and ultrasonically exfoliated for 8 h. Then, the aggregates were removed by centrifugation at 2000 rpm for 5 min and the supernatant was collected. The supernatant was then centrifuged at 10000 rpm for 30 min and the precipitate on the tube wall was collected to obtain boron nitride nanosheets (BNNS).

[0087] (3) Preparation of shape memory polyurethane fiber membranes (BNNS / SMPUFs)

[0088] The SMPU synthesized in step (1) was dissolved in hexafluoroisopropanol at 45°C for 2 hours, and BNNS was added according to the dosage in Table 1 and magnetically stirred for 1 hour. The obtained BNNS / SMPU precursor solution was drawn into a syringe and electrospun at a speed of 2 mL / h for 6 hours under a voltage environment of 35 kV. The spinneret was positive pressure 25 kV, the receiving drum was negative pressure 10 kV, the spinning environment temperature was 45°C, and the distance between the needle and the surface of the drum was 15 cm. The nanofibers were collected on a drum covered with aluminum foil at a speed of 3000 rpm. After spinning, the fiber membrane was peeled off from the aluminum foil, which is the shape memory polyurethane fiber membrane (BNNS / SMPUFs).

[0089] Table 1

[0090]

[0091] In Table 1, the doping amount of BNNS is the mass percentage of BNNS in the SMPU.

[0092] Figure 1 The image shows scanning electron microscope (SEM) images of the shape memory polyurethane fiber membrane samples 1-4 prepared above. It can be seen from the image that the membrane has a directionally extended fiber structure.

[0093] Figure 2 The figure shown is a differential scanning calorimetry (DSC) test result of the shape memory polyurethane fiber membrane samples 1-4 prepared above. It can be seen that the melting temperature range of the shape memory polyurethane fiber membrane is 20-50℃.

[0094] Figure 3 The figure shows the dielectric constant test results of shape memory polyurethane fiber membrane samples 1-4 with different boron nitride nanosheet doping amounts prepared above. It can be seen from the figure that the dielectric constant gradually increases with the increase of boron nitride nanosheet content, and the dielectric constant of all samples decreases with the increase of frequency and tends to stabilize at high frequency.

[0095] Figure 4The figure shows the test results of the non-contact sensing signal of the shape memory polyurethane fiber membrane samples 1-4 prepared above. The results were measured by an Agilent multimeter (model 34411A). It can be seen from the figure that the non-contact sensing voltage signal of the composite membrane sample 4 is the highest.

[0096] Example 2: Preparation of film-like composite material AgNWs-BNNS / SMPUFs-PDMS

[0097] (1) The shape memory polyurethane fiber membrane sample 4 prepared in Example 1 was pre-stretched to 100% strain at 50°C and then fixed at 15°C to complete the pre-programming and fixing.

[0098] (2) Mix polydimethylsiloxane (PDMS) and curing agent (PDMS184 curing agent) at a weight ratio of 10:1, spread them evenly on a glass plate, and place them in an 80℃ oven for 4 minutes to form a semi-cured state;

[0099] (3) A copper foil frame with a thickness of 60μm is attached to the shape memory polyurethane fiber membrane that has been fixed in step (1). The shape and size of the copper foil frame are the same as those of the shape memory polyurethane fiber membrane, but it is a frame structure that only contains four sides. The width of the four sides is 1 / 8 of the width of the shape memory polyurethane fiber membrane.

[0100] (4) A shape memory polyurethane fiber membrane is laminated on top of a semi-cured PDMS membrane, with the copper foil-coated side of the shape memory polyurethane fiber membrane facing the PDMS membrane, and placed at room temperature for 12 hours. During the placement process, the PDMS is completely cured and slightly permeates the shape memory polyurethane fiber membrane through diffusion, ultimately forming a strong BNNS / SMPUFs-PDMS composite membrane. The thickness of the shape memory polyurethane fiber membrane is 60 μm, and the thickness of the PDMS membrane is 1 mm.

[0101] (5) Plasma surface treatment was performed on the BNNS / SMPUFs of the BNNS / SMPUFs-PDMS composite membrane for 5 min. The 5 mol / L silver nanowire (AgNWs, diameter 90 nm, length 5 μm) aqueous dispersion was drop-coated and spread on the BNNS / SMPUFs of the BNNS / SMPUFs-PDMS composite membrane according to the dosage in Table 2 and allowed to penetrate. If the spreading was uneven during the process, it could be solved by plasma treatment for 5 min.

[0102] (6) After air drying at room temperature, the final film composite material AgNWs-BNNS / SMPUFs-PDMS is obtained. The layer formed after drying the silver nanowire aqueous dispersion is named the AgNWs layer.

[0103] Table 2

[0104]

[0105] The two ends of the AgNWs layer in the film-like composite material AgNWs-BNNS / SMPUFs-PDMS in Examples 2.0–2.3 are connected using conductive copper wire (e.g., Figure 9 As shown in the figure, a voltage of 2V was applied, and it was observed that the composite film underwent bending actuation driven by the electrothermal effect of the AgNWs layer network.

[0106] The thermal response actuation results of the BNNS / SMPUFs-PDMS composite membrane obtained in step (4) are shown in the figure. Figure 5 ,from Figure 5 As can be seen, the composite membrane responds within its melting temperature range. The higher the temperature, the greater the bending actuation angle produced by the composite membrane (the bending actuation angle is the angle at which the two ends of the sample form an arc, such as...). Figure 5 As shown in the figure below, the larger the angle, the less the bending actuation angle increases when the temperature is above 45℃.

[0107] In this embodiment, the time-electrothermal temperature curves of AgNWs layers with different resistances under 2V voltage for the film-like composite material AgNWs-BNNS / SMPUFs-PDMS are shown in the figure. Figure 6 The resistance values ​​in the figure correspond to those in Table 2. As can be seen from the figure, under the condition of applying a constant voltage of 2V, the temperature generated by the electric heating in Examples 2.0 to 2.2 is all below 50°C, which fails to reach the minimum temperature (45°C) required for the maximum bending actuation angle of the composite film. The temperature generated by the electric heating in Example S3 is as high as 53°C, which can reach the temperature required for the maximum bending actuation angle of the composite film.

[0108] The results of bending actuation generated by the electrothermal response of the film composite material AgNWs-BNNS / SMPUFs-PDMS in this embodiment are shown in the figure. Figure 7 It can be seen that after applying electrothermal stimulation to Example 2.3, the composite membrane can respond in real time, and the bending actuation angle increases with the increase of temperature.

[0109] In this embodiment, the film-like composite material AgNWs-BNNS / SMPUFs-PDMS, when energized (electric stimulation only), can respond to actuation in real time under the influence of electrothermal and thermal effects. Specifically, the test results of the film-like composite material AgNWs-BNNS / SMPUFs-PDMS in Example 2.3 on the induced electromotive force generated by the approach-and-away motion of a naturally charged object are shown below. Figure 8 As shown in the figure, the composite membrane can sense the approach and departure of objects, and maintains a continuous sensing signal while remaining close to the object. Its response time for approaching is 250ms, and its recovery time for moving away is 250ms. Figure 8The specific testing procedure is as follows: The positive electrode of an Agilent multimeter is connected to a copper foil with a copper wire, while the negative electrode is suspended in the air as a reference electrode. The initial vertical distance between the external charged object PTFE and the surface of the AgNWs-BNNS / SMPUFs-PDMS film composite material is 20 cm. During the approaching motion, the PTFE moves vertically towards the material surface until the vertical distance reaches 3 cm. The moving away motion is the opposite of the approaching motion, specifically returning to the initial point along the opposite trajectory. The multimeter measures the composite material's sensed electromotive force during this "approach-away" motion of the PTFE.

[0110] Example 3: Preparation of a non-contact sensor-actuator

[0111] The process and principle of fabricating non-contact sensor-actuator are as follows: Figure 10 As shown, construct the wiring (such as...) Figure 9 As shown, the material sensing signal is acquired and recorded in real time using an Agilent multimeter; secondly, the acquired signal is transmitted via USB and converted into a digital signal, and then output back to the material's electrothermal layer via an HLR-3003 programmable linear DC power supply to drive the material to actuate, thereby completing a non-contact "sensing-actuation" loop.

[0112] In this invention, when an external charged object approaches the film composite material AgNWs-BNNS / SMPUFs-PDMS, the dielectric properties of the "sensing-actuation" layer cause a polarization response to the external charged object. This is manifested as the local movement of charges within the layer under polarization, generating an electromotive force signal. This non-contact sensing signal is then output and returned to the material itself. The electrothermal effect of the AgNWs layer causes the system temperature to rise, thereby driving the material to generate a thermal response actuation. This achieves the fusion of non-contact "sensing-actuation" and prepares a non-contact sensing-actuator.

[0113] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a non-contact sensing-actuation composite material, characterized in that, Includes the following steps: S1. The shape memory fiber membrane is pre-stretched to produce deformation and then cooled and fixed to obtain the sensing-actuation layer; the shape memory fiber membrane is a shape memory polyurethane fiber membrane doped with dielectric particles. S2. An electrode is fabricated in a portion of the upper surface of the sensing-actuation layer; S3. Stack the sensing-actuation layer on the incompletely cured polydimethylsiloxane film and let it stand to allow the polydimethylsiloxane film to fully cure. The electrode face of the sensing-actuation layer is facing the incompletely cured polydimethylsiloxane film. S4. Coat the silver nanowire dispersion onto the surface of the sensing-actuation layer where no electrodes are prepared, and dry it to obtain the non-contact sensing-actuation composite material; In step S1, the dielectric particles are boron nitride nanosheets; the shape memory polyurethane fiber membrane is prepared by electrospinning from a precursor solution containing boron nitride nanosheets and shape memory polyurethane. The soft segments in the shape memory polyurethane are selected from any one of polycaprolactone polyols; the polycaprolactone polyol is polycaprolactone diol or polycaprolactone triol; the hard segments in the shape memory polyurethane are the product of the polycondensation reaction of diisocyanate and 1,4-butanediol, and the diisocyanate is selected from any one of diphenylmethyl diisocyanate, hexamethylene diisocyanate and isoflurone diisocyanate; The method for preparing the shape memory polyurethane includes the following steps: (1) Prepolymerize polycaprolactone polyol and diisocyanate; (2) The reaction continued after the addition of 1,4-butanediol.

2. The preparation method according to claim 1, characterized in that, The mass ratio of the soft segment to the hard segment is 70~80:20~30.

3. The preparation method according to claim 2, characterized in that, The mass ratio of the soft segment to the hard segment is 72:

28.

4. The preparation method according to claim 1, characterized in that, The total number of hydroxyl groups in the 1,4-butanediol and polycaprolactone polyol, and the molar ratio of isocyanate in the diisocyanate, are 1:1 to 1.

2.

5. The preparation method according to claim 4, characterized in that, The total number of hydroxyl groups in the 1,4-butanediol and polycaprolactone polyol is in a molar ratio of 1:1.05 to the isocyanate group in the diisocyanate.

6. The preparation method according to claim 1, characterized in that, The molecular weight of the polycaprolactone polyol is 3000~5000 g / mol.

7. The preparation method according to claim 1, characterized in that, In step (1), the reaction temperature of the prepolymerization is 80~100℃, and the reaction time of the prepolymerization is 2~3 h.

8. The preparation method according to claim 1, characterized in that, In step (2), the temperature for the continued reaction is 80~100℃, and the time for the continued reaction is 0.5~5 min.

9. The preparation method according to claim 1, characterized in that, The boron nitride nanosheets were prepared by liquid phase exfoliation.

10. The preparation method according to claim 9, characterized in that, The liquid phase exfoliation method includes the following steps: dispersing boron nitride in a solvent and exfoliating the boron nitride nanosheets by ultrasonic oscillation.

11. The preparation method according to claim 10, characterized in that, The duration of the ultrasonic oscillation is 6-12 hours.

12. The preparation method according to claim 1, characterized in that, The precursor liquid containing boron nitride nanosheets and shape memory polyurethane has a solid content of 5-15 wt%.

13. The preparation method according to claim 1, characterized in that, In the precursor solution containing boron nitride nanosheets and shape memory polyurethane, the mass of the boron nitride nanosheets is 3% to 8% of the mass of the polyurethane.

14. The preparation method according to claim 1, characterized in that, The solvent of the precursor solution is selected from any one of hexafluoroisopropanol, N,N-dimethylformamide, tetrahydrofuran, dichloromethane, and chloroform.

15. The preparation method according to claim 1, characterized in that, The ambient temperature for electrospinning is 45~60℃.

16. The preparation method according to claim 1, characterized in that, In the electrospinning process, the distance between the nozzle and the collector is 10-20 cm.

17. The preparation method according to claim 16, characterized in that, The collector is a rotating collector with a rotation speed of 1000~5000 rpm.

18. The preparation method according to claim 1, characterized in that, In step S1, the pre-stretching generates deformation to a strain of 100-300%.

19. The preparation method according to claim 1, characterized in that, The pre-stretching is performed at 35~80℃.

20. The preparation method according to claim 1, characterized in that, The cooling temperature is fixed at 0~15℃.

21. The preparation method according to claim 1, characterized in that, In step S3, the method for preparing the incompletely cured polydimethylsiloxane film includes the following steps: After mixing polydimethylsiloxane with the curing agent, pre-cur it at 80~120℃ for 3~5 min.

22. The preparation method according to claim 1, characterized in that, In step S3, the settling time is 8~24h.

23. The preparation method according to claim 1, characterized in that, In step S4, the silver nanowire dispersion comprises silver nanowires and a dispersant; the diameter of the silver nanowires is 30-90 nm and the length is 2-20 µm; the dispersant is selected from at least one of water, isopropanol, ethanol, cyclohexane and glycerol; the concentration of the silver nanowire dispersion is 0.1-100 mg / mL.

24. The preparation method according to claim 1, characterized in that, In step S4, the drying is air drying at room temperature.

25. The non-contact sensing-actuation composite material obtained by any of the preparation methods described in claims 1-24.

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