Flexible composite film, full-flexible dual-mode coupling sensor and preparation method

Abstract

The invention relates to the technical field of flexible sensors, and particularly discloses a flexible composite film, a full-flexible dual-mode coupling sensor and a preparation method of the full-flexible dual-mode coupling sensor. The full-flexible dual-mode coupling sensor provided by the invention is formed by weaving a flexible composite film; the flexible composite film comprises a bottom ionic liquid modified flexible polymer layer, a middle conductive layer and a top polymer layer, wherein the surface of the top polymer layer is provided with a periodic microstructure. The flexible sensor array is coupled with a contact separation and single-electrode dual-mode working mechanism, can realize high-precision identification, real-time pressure sensing and dynamic trajectory tracking of material types and surface textures at the same time, has a multi-parameter collaborative sensing function, is suitable for the fields of human-computer interaction, wearable electronics, intelligent robots and the like, and has wide application prospects. The potential application prospect is wide.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of flexible sensor, in particular to a flexible composite film, a full-flexible dual-mode coupled sensor and a preparation method thereof. BACKGROUND

[0002] With the rapid development and deep integration of Internet of Things and artificial intelligence technology, flexible sensors have become an important carrier in the fields of intelligent sensing and human-computer interaction. Compared with traditional rigid sensors, flexible sensors have excellent mechanical compliance, can maintain stable monitoring capability under complex deformation states such as bending, stretching and twisting, can closely adhere to irregular surfaces such as human skin and wearable device shells, and can meet real-time and accurate monitoring requirements. At the same time, the lightweight and thin characteristics of flexible sensors facilitate high-density integration, laying a foundation for the expansion of adaptive dynamic response, multi-functional integration and high-comfort application scenarios such as wearable health monitoring and flexible intelligent robot interaction.

[0003] Among various types of flexible sensors, flexible triboelectric sensors based on triboelectric nanogenerators stand out due to their unique working mechanism. These sensors can directly convert external mechanical excitations (such as pressure, strain and vibration) into electrical signal output through the coupling effect of contact electrification and electrostatic induction, without the need for additional power supply modules, thus realizing the integration of self-powered and sensing functions and showing broad application prospects in low-power portable sensing devices. However, existing flexible triboelectric sensors mainly rely on single output voltage detection mode, which is easily affected by mixed signals, resulting in limited sensing accuracy and insufficient reliability. In addition, most flexible array structure sensors have problems such as single sensing function, complex signal processing, low sensitivity and high cost. Moreover, most triboelectric sensors focus on energy harvesting or signal detection functions in a single working mode, and the application potential of multi-working mode coupling mechanism in intelligent interaction scenarios (such as material identification and dynamic trajectory tracking) has not been fully explored. Therefore, it is of great significance to develop a flexible triboelectric sensor array with multi-working mode coupling and excellent performance to improve the performance of flexible sensors in multi-parameter high-precision sensing and expand their applications in the fields of intelligent sensing and human-computer interaction. SUMMARY

[0004] In view of the problems of single sensing function, complex signal processing and low sensitivity of existing flexible array structure sensors, the present application provides a flexible composite film, a full-flexible dual-mode coupled sensor and a preparation method thereof.

[0005] To solve the above technical problems, the first aspect of the present application provides a flexible composite film, which comprises a flexible substrate layer, a conductive layer and a microstructure polymer layer from bottom to top.

[0006] The material of the flexible substrate layer comprises an ionic liquid modified flexible polymer; the material of the microstructured polymer layer comprises a flexible polymer, and a periodic protrusion or groove microstructure is arranged on a surface of the microstructured polymer layer away from the conductive layer.

[0007] Compared with the prior art, the flexible composite film provided by the application can provide structural support for the integration requirement of contact separation-single electrode dual-mode coupling, wherein the flexible substrate layer as the bottom layer provides basic mechanical support for the film, and at the same time, the flexible requirement is considered to ensure that the film can adapt to deformation when the two modes are switched, and structural damage in the mode coupling process is avoided. The conductive layer is located in the middle, not only bears the core function of converting and transmitting the physical signal to the electrical signal, but also is the pivot of the dual-mode coupling. In the contact separation mode, the conductive layer acts as a charge collection electrode to receive the triboelectric charge generated by the microstructured polymer layer in contact with the outside world; in the single electrode mode, the conductive layer directly acts as a sensing electrode to respond to the approach or departure of the charged object in the outside world, and the efficient transmission and cooperation of the charges and signals in the two modes are realized through the position of the intermediate layer. The microstructured polymer layer as the top layer directly interacts with the outside world through the periodic protrusion or groove microstructure on the surface: in the contact separation mode, the specific surface area in contact with the outside world is increased, and the amount of triboelectric charge generated is increased; in the single electrode mode, the microstructure enhances the electrostatic induction effect of the electrode and the outside world, and provides interface function support for the dual-mode coupling.

[0008] The bottom flexible substrate layer is made of an ionic liquid modified flexible polymer, which not only provides mechanical support and flexibility, but also optimizes the interface bonding stability of the conductive layer and the substrate layer through the interface charge regulation effect of the ionic liquid, reduces the damage of the conductive network during deformation; at the same time, the high conductivity of the ionic liquid can also assist in improving the conductivity stability of the overall film, avoiding the problem that the traditional flexible substrate layer can only provide support and has single function, and providing an environment for the stable existence and transmission of charges in the dual mode. The microstructured polymer layer is made of a flexible polymer compatible with the substrate layer, which ensures the interface bonding force with the intermediate conductive layer and avoids the peeling between the layers of heterogeneous materials; at the same time, the periodic protrusion or groove microstructure on the side away from the conductive layer can significantly increase the specific surface area of the film surface, which can increase the charge density of the triboelectricity in the triboelectric sensing scene, and can enhance the influence degree of deformation on the electrical signal in the pressure sensing scene.

[0009] The flexible composite film provided by the application can be widely applied to the fields of flexible sensors, wearable electronic devices, flexible displays and the like, and is especially suitable for scenes with the requirement of multi-mode sensing, and has strong industrial application potential.

[0010] Further, the ionic liquid is a bis(trifluoromethylsulfonyl) imide anion type functional ionic liquid.

[0011] Specifically, the ionic liquid is [EMIM]+ [TFSI] - or [DEME] + [TFSI] - .

[0012] The stable ionic conductivity of the preferred ionic liquid in the contact separation mode can assist in collecting the triboelectric charges generated by the contact of the microstructured polymer layer with the external environment, reducing the loss of charges in the transmission process, and improving the output intensity of the triboelectric signal; in the single electrode mode, the interface charge regulation ability can adjust the charge density on the surface of the conductive layer, enhance the electrostatic induction sensitivity of the conductive layer to the charged objects in the external environment, and broaden the detection range of the single electrode mode.

[0013] Further, the preparation method of the ionic liquid modified flexible polymer comprises the following steps: uniformly mixing the ionic liquid and the flexible polymer according to a predetermined ratio to obtain the ionic liquid modified flexible polymer.

[0014] Further, the flexible polymer in the flexible substrate layer and the microstructured polymer layer is independently selected from at least one of polydimethylsiloxane, thermoplastic polyurethane elastomer or polyvinylidene fluoride-hexafluoropropylene copolymer.

[0015] Specifically, the thermoplastic polyurethane elastomer is Ecoflex.

[0016] Further, in the material of the flexible substrate layer, the mass ratio of the ionic liquid to the flexible polymer is 1:10-1:20.

[0017] The addition ratio of the preferred ionic liquid not only ensures that the flexible substrate layer retains the excellent deformation ability of the polymer itself, but also precisely assists in the collection of triboelectric charges in the contact separation mode (reducing charge loss) and the electrostatic induction adjustment in the single electrode mode (optimizing charge density), avoiding weak sensing signals caused by insufficient ionic liquid and preventing signal interference caused by excessive ionic liquid.

[0018] Further, the material of the conductive layer is selected from at least one of carbon nanotubes, Ti3C2T x or nitrogen-doped reduced graphene oxide.

[0019] The preferred conductive material has high conductivity and good conductivity stability, and at the same time, has good flexibility and dispersibility, can form a stable combination with the flexible substrate layer and the microstructured polymer layer of the thin film, and avoid the decrease of the flexibility of the thin film caused by the rigidity of the material; in addition, it has a large specific surface area and more defect sites, which can improve the collection efficiency of triboelectric charges in the contact separation mode and enhance the induction sensitivity in the single electrode mode.

[0020] Further, the aspect ratio of the carbon nanotube is 102 ~10 5 The nitrogen-doped reduced graphene is a single-layer structure, with a single-layer area of 10 3 ~10 6 nm 2 and a single-layer thickness of 10nm-100nm.

[0021] It should be noted that the nitrogen-doped reduced graphene in the present application can be prepared by using the existing disclosed method or commercially available product, and the present application is not specially limited.

[0022] Further, the thickness ratio of the flexible substrate layer to the conductive layer is 3:1-10:1, and the thickness ratio of the conductive layer to the microstructure polymer layer is 1:5-1:20.

[0023] The preferred thickness of each layer can ensure that the film can be coiled and folded without interlayer peeling, and can also enhance the physical signal and reduce the transmission attenuation.

[0024] In a second aspect, the present application provides a preparation method of the flexible composite film, comprising the following steps:

[0025] S1, applying a conductive paste to a substrate to form a conductive layer on the substrate;

[0026] S2, coating a flexible polymer solution on one side surface of the conductive layer, pre-solidifying the peeled film, forming a pre-solidified film on the conductive layer, using a microstructure template to press a periodic microstructure on the surface of the pre-solidified film, solidifying, peeling off the microstructure template, forming a microstructure polymer layer on the conductive layer, and peeling off the substrate;

[0027] S3, using a silk screen printing process to coat an ionic liquid modified flexible polymer on the other side surface of the conductive layer and the microstructure polymer layer, solidifying, forming a flexible substrate layer on the other side surface of the conductive layer, and obtaining a flexible composite film.

[0028] The application provides a preparation method of a flexible composite film, which comprises the following steps: firstly, coating conductive paste to a substrate to form a uniform conductive layer; then coating a flexible polymer solution on one side of the conductive layer, and sequentially performing pre-solidification, microstructure imprinting and complete solidification treatment to form a microstructure polymer layer containing micro-nano structures, the micro-nano structures can significantly expand the pressure sensing range of the film and improve the sensitivity, so that the film can meet the monitoring requirements of the roughness or texture of the surface of an object; finally, coating an ionic liquid modified flexible polymer on the other side of the conductive layer by using a screen printing process; at this time, the conductive layer has been fixed by the microstructure polymer layer, the pressure of screen printing can uniformly act on the conductive layer, so as to ensure that the flexible substrate layer and the conductive layer are closely combined, meanwhile, the ionic liquid can fully penetrate into the interface between the two layers, and the interface charge regulation effect is optimized; and the flexible substrate layer and the microstructure polymer layer are both made of full flexible materials, which lays a foundation for the flexibility of the whole composite film.

[0029] Specifically, in S1, the substrate is a glass substrate.

[0030] Specifically, in S1, the conductive paste is prepared by dispersing a conductive material in an organic solvent; the conductive material is at least one selected from carbon nanotubes, Ti3C2Tx x or nitrogen-doped reduced graphene oxide.

[0031] Preferably, the concentration of the conductive paste is 20 mg / mL-50 mg / mL.

[0032] Further, the thickness of the conductive layer is 10 μm-50 μm; the thickness ratio of the flexible substrate layer to the conductive layer is 3:1-10:1, and the thickness ratio of the conductive layer to the microstructure polymer layer is 1:5-1:20.

[0033] Specifically, in S1-S3, the coating is performed by using a doctor blade method.

[0034] Further, the microstructure template is a stripe grid, a pyramid array, a biomimetic texture or a columnar array.

[0035] In a third aspect, the application provides a full flexible dual-mode coupling sensor array, which is cut into a strip unit from the flexible composite film according to any one of the above-mentioned aspects, and is formed into an array structure by three-dimensional interlacing weaving.

[0036] The interlaced nodes of the strip-shaped units can serve as independent local sensing units. When external contact excitation acts on the array, the interlaced structure can accurately disperse the contact force, so that the conductive layer of each node is more likely to trigger the single-electrode mode (sensing external contact) and the contact separation mode (realizing internal energy conversion). Compared with a planar array, the three-dimensional contact interface of the interlaced structure can significantly shorten the activation response time of the two modes, and relying on the unobstructed electrical signal conduction path of the interlaced network, the synchronous charge transfer effect is further strengthened, so that the overall output signal strength of the array is significantly enhanced. In addition, the strip-shaped units completely retain the periodic micro-nano structure of the original film surface, and the pore structure formed by the three-dimensional interweaving can further expand the contact area of the pressure action. When pressure acts on the array, the deformation of the interlaced unit can be transmitted to more local sensing nodes through the pores, not only effectively widening the pressure sensing range and improving the sensitivity, but also accurately identifying different directions of pressure such as vertical pressure and shear force, successfully solving the defects of single direction and limited range of pressure sensing of the planar array.

[0037] Further, the preparation method of the full-flexible dual-mode coupled sensor array comprises the following steps:

[0038] S1, coating a conductive paste on a substrate to form a conductive layer on the substrate;

[0039] S2, coating a flexible polymer solution on one side surface of the conductive layer, pre-solidifying the peeled film, forming a pre-solidified film on the conductive layer, using a microstructure template to press a periodic microstructure on the surface of the pre-solidified film, solidifying, peeling off the microstructure template, forming a microstructure polymer layer on the conductive layer, and peeling off the substrate;

[0040] S3, coating an ionic liquid modified flexible polymer on the other side surface of the conductive layer and the microstructure polymer layer using a screen printing process, solidifying, forming a flexible base layer on the other side surface of the conductive layer, and obtaining a flexible composite film;

[0041] S4, cutting the flexible composite film into strip-shaped units according to the screen printing lines on the surface of the flexible base layer, interweaving into a three-dimensional interlaced network array, and obtaining a full-flexible dual-mode coupled sensor array.

[0042] Further, in S4, the interweaving can adopt an alternating interweaving method or horizontal and vertical interweaving into a three-dimensional interlaced network array. The three-dimensional interlaced network array can serve as a friction nanogenerator, forming a full-flexible dual-mode coupled frictional interwoven sensing array with two working modes of contact separation and single-electrode.

[0043] The full-flexible dual-mode coupled sensor array provided by the application has high sensing precision, can increase the friction contact area through the periodic convex or groove microstructure on the surface of the microstructure polymer layer, and can combine the interface charge regulation effect of the ionic liquid in the flexible substrate layer to construct a coupling mechanism of contact separation and single electrode two working modes, accurately capture physical signals such as pressure, strain and vibration, effectively avoid signal interference and precision attenuation problems in a single mode, and thus realize high-precision perception of multiple parameters. In addition, the full-flexible dual-mode coupled sensor array can be coiled, folded and stretched, can adapt to the use requirements of irregular surfaces such as human skin and wearable devices, and has the advantages of simple preparation method, low cost, simple process flow and suitability for large-scale production and application.

[0044] In a fourth aspect, the application provides a full-flexible dual-mode coupled sensor, comprising the flexible composite film according to any one of the above or the full-flexible dual-mode coupled sensor array.

[0045] The full-flexible dual-mode coupled sensor array of the application is cut into a strip-shaped unit by using a flexible composite film containing a periodic micro-nano structure, and is formed into an array structure by three-dimensional interlacing weaving. When an object contacts the interlaced network, a single electrode mode for sensing external contact and a contact separation mode for internal energy conversion can be activated in sequence, and the charge transfer directions are consistent to realize synchronous charge transfer, so that the overall output performance of the device is significantly higher than that of a single mode, and the two working modes can simultaneously sense and identify two or more parameters, having a multi-modal sensing function. The array has good flexibility, can be repeatedly bent, stretched and twisted, can adapt to various irregular surfaces, and has biocompatibility and environmental adaptability. The three-dimensional pressure sensing system based on the array has excellent mechanical compliance and pressure response characteristics, can realize dynamic trajectory printing and real-time pressure field mapping, and has great application potential in the fields of robots, wearable devices and the like. In addition, the array preparation process is simple to operate and low in processing cost, is beneficial to industrialized production, and the array row and column layout can be adjusted as needed, the shape can be arbitrarily cut according to the application occasion, the structure can be customized, and has wide application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 Flowchart for preparing the full-flexible dual-mode coupled woven sensor array of the embodiment;

[0047] Figure 2 Structure diagram of the full-flexible dual-mode coupled woven sensor array prepared in Example 1;

[0048] Figure 3 Surface micro-morphology diagram of the flexible composite film prepared in Example 1 at different magnifications;

[0049] Figure 4The photos of the full-flexible dual-mode coupling woven sensing array prepared in Example 1, and the photos of the strip units obtained by cutting after stretching and bending; (a) the photo of the full-flexible dual-mode coupling woven sensing array, (b) the photo of the bending, (c) the photo of the stretching;

[0050] Figure 5 The comparison chart of the electrical output performance of the full-flexible dual-mode coupling woven sensing array prepared in Example 1 in different working modes;

[0051] Figure 6 The relationship chart of the pressure and the voltage of the full-flexible dual-mode coupling woven sensing array prepared in Example 1 in the single electrode mode and the contact separation mode;

[0052] Figure 7 The voltage curve chart of the output of the full-flexible dual-mode coupling woven sensing array in Example 1 contacted by objects with different surface roughnesses;

[0053] Figure 8 The voltage curve chart of the output of the full-flexible dual-mode coupling sensing array in Example 1 contacted by 12 kinds of objects under different pressures;

[0054] Figure 9 The sensing chart of the full-flexible dual-mode coupling woven sensing array in Example 1 to different pressure positions and sizes. DETAILED DESCRIPTION

[0055] In order to make the objects, technical solutions and advantages of the present application clearer, the following further describes the present application with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0056] In order to better illustrate the present application, the following further illustrates the present application by way of examples.

[0057] Example 1

[0058] The present embodiment provides a flexible composite film, which comprises, from bottom to top, a flexible substrate layer, a conductive layer and a microstructure polymer layer;

[0059] The material of the flexible substrate layer is [EMIM] + [TFSI] - Modified polydimethylsiloxane, [EMIM] + [TFSI] - The mixing mass ratio of polydimethylsiloxane is 1:10;

[0060] The material of the conductive layer is nitrogen-doped reduced graphene oxide;

[0061] The material of the microstructured polymer layer is polydimethylsiloxane, and one surface of the microstructured polymer layer away from the conductive layer is provided with a periodic convex or concave microstructure.

[0062] The thickness of the conductive layer is 30 μm; the thickness ratio of the flexible substrate layer to the conductive layer is 4:1, and the thickness ratio of the conductive layer to the microstructured polymer layer is 1:5.

[0063] The application also provides a full-flexible dual-mode coupling sensor array, which is cut into a strip unit from the flexible composite film, and is formed into an array structure through three-dimensional interlacing weaving, and the specific preparation steps are as follows:

[0064] S1, 0.1 g of nitrogen-doped reduced graphene oxide nanomaterial is added into anhydrous ethanol, and ultrasonic dispersion is performed for 30 min to obtain a nitrogen-doped reduced graphene oxide dispersion liquid of 20 mg / mL; a glass substrate is cleaned with anhydrous ethanol, the cleaned glass substrate is heated and dried at 60 DEG C, then a layer of the prepared nitrogen-doped reduced graphene oxide dispersion liquid is scraped on the glass substrate, the scraper thickness is 50 μm, and the glass substrate is heated and dried at 60 DEG C for 15 min, and then naturally cooled to room temperature to form a conductive layer on the glass substrate;

[0065] S2, polydimethylsiloxane is coated on one side of the surface of the prepared conductive layer, the scraper thickness is 200 μm, and then the prepared film is placed in a 60 DEG C oven for pre-curing for 5 min to obtain a pre-cured film;

[0066] S3, a grating film with a stripe grid is laid on the surface of the prepared pre-cured film to form a microstructure on the pre-cured film by imprinting, wherein the pitch of the microstructure on the surface of the grating film is 160 μm, the grating film is placed in an oven for curing, cooled, and then the grating film and the glass substrate are peeled off to obtain a flexible composite film with a conductive layer on one surface and a periodic microstructure on the other surface;

[0067] S4, the conductive layer of the prepared flexible composite film is laid upward, printing is performed by using a silk screen with a square alternately arranged, the silk screen template size is 50 mm x 50 mm, the internal rectangular unit size is 10 mm x 10 mm, and the mixture of the ionic liquid and the polydimethylsiloxane with a mass ratio of 1:10 is coated on the flexible composite film by using a scraper with a thickness of 150 μm, the printed wet film is heated and cured, and then cooled to obtain a flexible composite film; + [TFSI] - [TFSI] - The mixture of the ionic liquid and the polydimethylsiloxane with a mass ratio of 1:10 is coated on the flexible composite film by using a scraper with a thickness of 150 μm, the printed wet film is heated and cured, and then cooled to obtain a flexible composite film;

[0068] S5, the flexible composite film prepared above is cut into strip units according to the lines of the screen printing template, the size of the strip unit is 10 cm x 50 cm x 300 μm, a group of strip units are laid in parallel along the horizontal direction as the lower layer substrate, then another group of strip units with the same specification are woven on the former in the vertical direction in an alternating interlaced manner, and a three-dimensional interlaced network structure is assembled. The interlaced area forms a friction interface coupled with the contact separation and single electrode two working modes. During the entire weaving process, the cross node positions are strictly corresponding to the rectangular units to ensure the regularity and consistency of the array structure. The interlaced area is in the shape of an array, and a full-flexible dual-mode coupled woven sensing array is formed, with a thickness of 600 μm.

[0069] The full-flexible dual-mode coupled woven sensing array prepared according to the above preparation method (process flow chart as shown in Figure 1 ) forms a layered structure, and the specific structure schematic diagram is shown in Figure 2 From the cross-sectional schematic diagram, it can be seen that in the assembled flexible sensor array structure, the microstructured polymer layer (polydimethylsiloxane layer with periodic microstructure) on the upper surface of the lower flexible composite film and the flexible substrate layer (ionic liquid modified polydimethylsiloxane layer) on the lower surface of the upper flexible composite film constitute the contact-separation working mode of triboelectricity, and the ionic liquid modified polydimethylsiloxane layer with surface periodic microstructure on the upper flexible composite film and the external contact object constitute the single electrode working mode of triboelectricity.

[0070] As can be seen from the optical photograph in Figure 3 , the flexible composite film as a whole has good compactness and structural integrity, and no obvious cracks or interface defects are observed. It can be clearly seen that the flexible composite film has a three-layer structure, the upper layer corresponds to the polydimethylsiloxane layer with periodic microstructure, the middle layer corresponds to the reduced graphene oxide nanometer conductive layer, and the bottom layer corresponds to the ionic liquid modified polydimethylsiloxane layer.

[0071] As can be seen from the optical photograph in Figure 4 , the full-flexible dual-mode coupled woven sensing array based on the flexible composite film has good flexibility and can be repeatedly bent, stretched and twisted to deform, and can adapt to various irregular surfaces. The conductive layer in the flexible composite film has good conductivity and can be used as the electrode layer of the device, so that no additional electrode is needed in the dual-working-mode triboelectric nanogenerator assembly and the sensor array. The full-flexible sensing array based on the flexible composite film couples the contact separation and single electrode two working modes.

[0072] The electrical output performance of the full-flexible dual-mode coupling woven sensor array prepared in this example was tested by applying a vertical load using a linear motor (KLDMF42-500) and controlling the displacement and frequency. The output voltage, current and transferred charge were recorded by a programmable electrometer (Keithley 6517B) and input into a computer for processing. The pressure was measured by a pressure sensor (SBT673, SIMBATOUCH) and a dynamic signal analyzer (DH8303N, Donghua) to measure the signal output of the device under different pressures. The electrode of the single-electrode working mode device was led out from the conductive layer in the upper layer of the flexible composite film. During the test, the external contact object was in contact with and separated from the upper surface of the flexible composite film. One end of the dynamic signal analyzer was connected to the conductive layer, and the other end was grounded, which was used to collect the output signal and perform data analysis.

[0073] The electrodes of the contact-separation working mode device were led out from the conductive layers in the upper and lower layers, respectively. Under external excitation, the lower surface of the upper layer of the flexible composite film was in contact with and separated from the upper surface of the lower layer of the flexible composite film, which together constituted a contact-separation working interface. During the test, one end of the multi-channel dynamic signal analyzer was connected to the conductive layer of the lower layer of the flexible composite film, and the other end was connected to the conductive layer of the upper layer of the flexible composite film, which was used to collect the output characteristic test. In this working mode, the external object was always in contact with the upper layer of the flexible composite film, the single electrode was not working, and only the contact-separation mode was working.

[0074] The electrodes of the coupling working mode device were still led out from the conductive layers of the upper and lower layers of the flexible composite film and connected to the multi-channel dynamic signal analyzer to collect signals, and the lower electrode was equivalent to ground at this time. Unlike the contact-separation working mode, the external object was in contact with and separated from the surface, first the external object contacted the sensor array surface to form a single-electrode working mode, and the upper layer of the flexible composite film accumulated electric charge, i.e., the single-electrode mode accumulated electric charge. When the upper and lower layers of the flexible composite film were in contact, a contact-separation working mode was formed, and the electric charge was transferred in the loop after the two layers were separated. The sequential working of the single-electrode working mode and the contact-separation working mode made the direction of the charge transfer in the loop the same, and the time sequence superposition enhanced the output. As shown in Figure 5 the output peak voltage of the pure single-electrode working mode device, the pure contact-separation working mode device and the coupling working mode device was 46.1 V, 17.6 V and 69.5 V, respectively, and the output power density was 0.38 W / m 2 , 0.09 W / m 2 and 0.55 W / m 2 , respectively. The coupling working mode device exhibited the highest output performance.

[0075] The sensitivity of the device was tested under different pressure conditions. In the low pressure region, the sensitivity of the single electrode mode device was 1.48V / kPa, and the contact separation mode device was 0.7V / kPa; in the high pressure region, the sensitivity of the two devices was 0.06V / kPa, indicating that the device had good pressure response characteristics, as shown in Figure 6 The array sensor has high sensitivity and linearity and can sense small pressure.

[0076] As shown in Figure 7 The full-flexible dual-mode coupled woven sensing array can identify the voltage signals of carbon steel samples with different surface roughness (Ra 0.8, Ra 1.6, Ra 3.2 and Ra 6.3). When in contact with rough surfaces, periodic oscillations of the sensing signal are generated due to the uneven fluctuations of friction force and the subtle changes in relative motion speed, which is used as an important physical parameter for surface texture recognition.

[0077] Figure 8 The contact sensing array voltage curves of 12 different materials are shown, where the voltage size directly reflects the number of transferred charges. The more the transferred charges, the higher the output voltage. To further improve the accuracy of material recognition, the BiLSTM deep learning algorithm is introduced. For each group of material samples, a total of 100 independent time series samples are collected, each containing 10 time steps and 100 feature dimensions. These samples are randomly divided into a training set (80 groups) and a test set (20 groups) in the ratio of 8:2. After iterative training, the confusion matrix recognition accuracy of the 12 materials reaches 92.5%, and the real-time coupling of the contact separation mode and the single electrode mode has practical application value in the fields of roughness recognition and material recognition.

[0078] When pressure is applied to different positions of the woven array sensor, the generated electrical signal is first processed by a transistor amplifier circuit, and then transmitted to an analog port on an Arduino MEGA 2560 microcontroller. The microcontroller detects the voltage signal through its port and sends the detected signal to a computer. After pressure recognition and detection, parity check and weighted fusion processing on the computer, the final real-time detection result is output. As shown in Figure 9 Dynamic trajectory tracking tests using the constructed three-dimensional pressure sensing system show that the system can accurately capture the position and pressure of the press, achieving high-resolution pressure dynamic trajectory mapping.

[0079] Embodiment 2

[0080] The embodiment provides a flexible composite film, which comprises, from bottom to top, a flexible substrate layer, a conductive layer and a microstructured polymer layer;

[0081] The material of the flexible substrate layer is [EMIM] + [TFSI] - Modified PVDF-HFP, [EMIM] + [TFSI] - The mixed mass ratio of PVDF-HFP is 1:15;

[0082] The material of the conductive layer is Ti3C2T x ;

[0083] The material of the microstructured polymer layer is PVDF-HFP, and the microstructured polymer layer is provided with a periodic convex or groove microstructure on one surface away from the conductive layer.

[0084] The thickness of the conductive layer is 10 μm; the thickness ratio of the flexible substrate layer to the conductive layer is 10:1, and the thickness ratio of the conductive layer to the microstructured polymer layer is 1:10.

[0085] The application also provides a full-flexible dual-mode coupling sensor array, which is cut into a strip unit from the flexible composite film, and is formed into an array structure through three-dimensional interlacing weaving, and the specific preparation steps are as follows:

[0086] S1, 0.5g Ti3C2T x is added into N-methyl pyrrolidone, and ultrasonic dispersion is performed for 30 min to obtain a Ti3C2T x dispersion liquid; a glass substrate is cleaned by ultrasonic cleaning with anhydrous ethanol, the cleaned glass substrate is heated and dried at 60 DEG C, and then a layer of the prepared Ti3C2T x dispersion liquid is scraped on the glass substrate, the scraper thickness is 50 μm, the glass substrate is heated and dried at 60 DEG C for 15 min, and then naturally cooled to room temperature to form a conductive layer on the glass substrate;

[0087] S2, PVDF-HFP is coated on one surface of the prepared conductive layer, the scraper thickness is 200 μm, and then the conductive layer is placed in an oven at 60 DEG C for pre-curing for 5 min to obtain a pre-cured film;

[0088] S3, a grating film with a columnar array is laid on the surface of the prepared pre-cured film, and a microstructure is formed on the pre-cured film by imprinting, wherein the pitch of the microstructure on the surface of the grating film is 50 μm, the pre-cured film is placed in an oven for curing, cooled, and the grating film and the glass substrate are peeled off to obtain a flexible composite film which is conductive on one surface and has a periodic microstructure on the other surface;

[0089] S4, the conductive layer of the flexible composite film prepared above is laid flat with the conductive layer facing up, printing is performed using a screen with a square alternating arrangement, the screen template size is 50 mm x 50 mm, the internal square cell size is 10 mm x 10 mm, and the flexible composite film is coated with [EMIM] + [TFSI] - The mixture of the ionic liquid and the PVDF-HFP is coated on the flexible composite film using a doctor blade with a thickness of 150 μm, the printed wet film is heated and cured, and then cooled to obtain a flexible composite film.

[0090] S5, the flexible composite film prepared above is cut into strip units according to the lines of the screen printing template, the size of the strip unit is 10 cm x 50 cm x 210 μm, a group of strip units is laid flat in the horizontal direction as the lower layer, and then another group of strip units with the same specifications is woven on the former in the vertical direction in an alternating manner to assemble a three-dimensional interwoven network structure. The staggered areas form a friction interface that couples the contact separation and single electrode two working modes. During the entire weaving process, the cross node positions strictly correspond to the square units to ensure the regularity and consistency of the array junction structure. The staggered areas are in the form of an array, and constitute a full-flexible dual-mode coupled woven sensing array with a thickness of 420 μm.

[0091] The flexible composite film prepared by the above preparation method forms a layered structure, and the assembled flexible sensor array structure has a periodic microstructure PVDF-HFP layer on the upper surface of the lower flexible composite film and an ionic liquid modified PVDF-HFP layer on the lower surface of the upper flexible composite film, which constitutes a triboelectric contact-separation working mode, and the upper flexible composite film has a periodic microstructure PVDF-HFP layer on the surface and contacts with the external object, which constitutes a triboelectric single electrode working mode.

[0092] The output power density of the full-flexible dual-mode coupled woven sensing array device prepared in this example is tested according to the method of Example 1, and the results show that the peak output power densities of the single electrode working mode device, the contact separation working mode device and the coupled working mode device are 0.31 W / m 2 , 0.11 W / m 2 and 0.45 W / m 2The coupling working mode device exhibits the highest output performance. Sensitivity tests are performed on the device under different pressure conditions. In the low pressure region, the sensitivity of the single electrode working mode device is 1.28 V / kPa, and the sensitivity of the contact separation working mode device is 0.62 V / kPa. In the high pressure region, the sensitivity of the two devices is 0.05 V / kPa, indicating that the device has good pressure response characteristics. The array sensor has high sensitivity and linearity and can sense small pressure. The three-dimensional pressure sensing system is used for dynamic trajectory tracking test, and the system can accurately capture the trajectory of the handwritten character, and realizes high-resolution dynamic trajectory mapping.

[0093] Embodiment 3

[0094] The flexible composite film comprises, from bottom to top, a flexible substrate layer, a conductive layer and a microstructure polymer layer.

[0095] The material of the flexible substrate layer is [DEME] + [TFSI] - modified Ecoflex, [DEME] + [TFSI] - The mixing mass ratio of Ecoflex is 1:20.

[0096] The material of the conductive layer is carbon nanotubes.

[0097] The material of the microstructure polymer layer is Ecoflex, and one surface of the microstructure polymer layer away from the conductive layer is provided with a periodic convex or groove microstructure.

[0098] The thickness of the conductive layer is 50 μm; the thickness ratio of the flexible substrate layer to the conductive layer is 6:1, and the thickness ratio of the conductive layer to the microstructure polymer layer is 1:20.

[0099] The application also provides a full-flexible dual-mode coupling sensor array, which is cut into a strip unit from the above flexible composite film, and is formed into an array structure through three-dimensional interlacing weaving, and the specific preparation steps are as follows:

[0100] S1, 0.3g of carbon nanotubes is added to anhydrous ethanol, and ultrasonic dispersion is performed for 30min to obtain a carbon nanotube dispersion liquid of 30mg / mL; the cleaned glass substrate is heated and dried at 60℃, then a layer of the above prepared carbon nanotube dispersion liquid is scraped on the glass substrate, the scraper thickness is 100 μm, and the glass substrate is heated and dried at 60℃ for 15min, and then naturally cooled to room temperature to form a conductive layer on the glass substrate;

[0101] S2, coating Ecoflex on the surface of the conductive layer prepared above, the doctor blade thickness is 1200 pm, then pre-curing in the oven at 60°C for 5 min, to obtain a pre-cured film;

[0102] S3, laying the grating film with stripe grid on the surface of the pre-cured film prepared above, imprinting microstructure on the pre-cured film, wherein the pitch of the microstructure on the surface of the grating film is 160 pm, curing in the oven, cooling, peeling the grating film and the glass substrate, to obtain a flexible composite film with conductive surface and periodic microstructure on the other side;

[0103] S4, laying the flexible composite film prepared above with the conductive layer upward, printing by using the silk screen with square alternately arranged screen, the size of the silk screen template is 50 mm x 50 mm, the size of the square unit inside is 10 mm x 10 mm, coating the mixture of the ionic liquid and Ecoflex with the mass ratio of 1:20 on the surface of the flexible composite film, heating and curing the wet film after printing, and cooling to obtain a flexible composite film; + [TFSI] - The mixture of the ionic liquid and Ecoflex, the doctor blade thickness is 400 pm, heating and curing the wet film after printing, and cooling to obtain a flexible composite film;

[0104] S5, cutting the flexible composite film prepared above into strip units according to the lines of the silk screen printing template, the size of the strip unit is 10 cm x 50 cm x 1350 pm, laying a group of strip units in parallel as the lower base along the horizontal direction, then weaving another group of strip units with the same specification on the former in the form of alternating interlacing along the vertical direction, to assemble a three-dimensional interlaced network structure. The interlaced area forms a triboelectric interface coupled with the contact-separation and single-electrode two working modes. During the whole weaving process, the cross node positions strictly correspond to the square units, to ensure the regularity and consistency of the array junction structure. The interlaced area is in the form of array, to constitute a full-flexible dual-mode coupled woven sensing array, with the thickness of 2700 pm.

[0105] The flexible composite film prepared by the above preparation method forms a layered structure, in the flexible sensor array structure assembled, the Ecoflex layer with periodic microstructure on the upper surface of the lower flexible composite film and the ionic liquid modified Ecoflex layer on the lower surface of the upper flexible composite film constitute the triboelectric contact-separation working mode, and the Ecoflex layer with periodic microstructure on the surface of the upper flexible composite film and the external contact object constitute the triboelectric single-electrode working mode.

[0106] The output power density of the full-flexible dual-mode coupled woven sensing array device prepared in this example is tested according to the method of Example 1, and the results show that the peak output power densities of the single-electrode working mode device, the contact-separation working mode device and the coupled working mode device are 0.31 W / m2 0.11 W / m 2 and 0.53 W / m 2 The coupling working mode device exhibits the highest output performance. Sensitivity tests are performed on the device under different pressure conditions. In the low pressure region, the sensitivity of the single electrode working mode device is 0.98 V / kPa, and the contact separation working mode device is 0.71 V / kPa. In the high pressure region, the sensitivity of the single electrode working mode device is 0.08 V / kPa, and the contact separation working mode device is 0.06 V / kPa, indicating that the device has good pressure response characteristics. The array sensor has high sensitivity and linearity, and can sense small pressure. The three-dimensional pressure sensing system is used for dynamic trajectory tracking test, and the system can accurately capture the trajectory of the handwritten character, realizing high-resolution dynamic trajectory mapping.

[0107] The above merely describes preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement or improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A flexible composite film, characterized in that, From bottom to top, it includes a flexible substrate layer, a conductive layer, and a microstructured polymer layer; The flexible substrate layer is made of an ionic liquid-modified flexible polymer; the microstructure polymer layer is made of a flexible polymer, and the surface of the microstructure polymer layer away from the conductive layer is provided with periodic protrusions or grooves.

2. The flexible composite film as described in claim 1, characterized in that, The ionic liquid is a bis(trifluoromethanesulfonyl)imide anionic functionalized ionic liquid; and / or The flexible polymers in the flexible substrate layer and the microstructure polymer layer are each independently selected from at least one of polydimethylsiloxane, thermoplastic polyurethane elastomer, or polyvinylidene fluoride-hexafluoropropylene copolymer; and / or The conductive layer is made of carbon nanotubes, Ti3C2T... x Or at least one of nitrogen-doped reduced graphene oxide.

3. The flexible composite film as described in claim 2, characterized in that, The ionic liquid is [EMIM]. + [TFSI] - Or [DEME] + [TFSI] - ; and / or In the material of the flexible substrate layer, the mass ratio of ionic liquid to flexible polymer is 1:10 to 1:

20.

4. The flexible composite film as described in claim 1, characterized in that, The thickness ratio of the flexible substrate layer to the conductive layer is 3:1 to 10:1, and the thickness ratio of the conductive layer to the microstructure polymer layer is 1:5 to 1:

20.

5. The method for preparing the flexible composite film according to any one of claims 1 to 4, characterized in that, Includes the following steps: S1, The conductive paste is coated onto the substrate to form a conductive layer on the substrate; S2, a flexible polymer solution is coated on one side of the conductive layer, the peeled film is pre-cured to form a pre-cured film on the conductive layer, a periodic microstructure is imprinted on the surface of the pre-cured film using a microstructure template, the film is cured, the microstructure template is peeled off, a microstructure polymer layer is formed on the conductive layer, and the substrate is peeled off. S3, an ionic liquid-modified flexible polymer is coated on the opposite surface of the conductive layer and the microstructure polymer layer using a screen printing process, and then cured to form a flexible substrate layer on the other side of the conductive layer, thus obtaining a flexible composite film.

6. The method for preparing the flexible composite film as described in claim 5, characterized in that, The thickness of the conductive layer is 10μm to 50μm; the thickness ratio of the flexible substrate layer to the conductive layer is 3:1 to 10:1; and the thickness ratio of the conductive layer to the microstructure polymer layer is 1:5 to 1:

20.

7. The method for preparing the flexible composite film as described in claim 5, characterized in that, The microstructure template is a striped grid, a pyramid array, a biomimetic texture, or a columnar array.

8. A fully flexible dual-mode coupled sensor array, characterized in that, After the flexible composite film described in any one of claims 1 to 4 is cut into strip-shaped units, an array structure is formed by three-dimensional interweaving.

9. The fully flexible dual-mode coupled sensor array according to claim 8, characterized in that, Its preparation method includes the following steps: S1, The conductive paste is coated onto the substrate to form a conductive layer on the substrate; S2, a flexible polymer solution is coated on one side of the conductive layer, the peeled film is pre-cured to form a pre-cured film on the conductive layer, a periodic microstructure is imprinted on the surface of the pre-cured film using a microstructure template, the film is cured, the microstructure template is peeled off, a microstructure polymer layer is formed on the conductive layer, and the substrate is peeled off. S3, an ionic liquid modified flexible polymer is coated on the other side of the conductive layer and the microstructure polymer layer using a screen printing process, and then cured to form a flexible substrate layer on the other side of the conductive layer, thus obtaining a flexible composite film. S4. According to the screen-printed pattern on the surface of the flexible substrate, the flexible composite film is cut into strip units and woven into a three-dimensional interwoven network array to obtain a fully flexible dual-mode coupled sensor array.

10. A fully flexible dual-mode coupling sensor, characterized in that, Includes the flexible composite film according to any one of claims 1 to 4 or the fully flexible dual-mode coupled sensor array according to claim 8.

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