CN118347611A - Method for constructing flexible pressure sensor by direct-writing printing micro-nano depression template - Google Patents

Abstract

The invention provides a method for constructing a flexible pressure sensor by directly writing and printing micro-nano concave templates in a bionic mode, and relates to the field of pressure sensors, comprising the following steps of: s1, preparing a support material substrate; s2, preparing a viscoelastic fluid; s3, pre-curing; s4, setting printing parameters to print to obtain a template with a micro-nano concave structure; s5, modification treatment; s6, solidifying; s7, preparing a flexible electrode; s8, preparing the ultra-sensitive multi-layer multi-mode flexible pressure sensor. The invention prints the controllable micro-nano concave structure on the surface of the viscoelastic substrate by direct writing printing, thereby constructing the flexible electrode with the micro-nano convex structure, improving the performance of the sensor and realizing the preparation of the ultra-sensitive multi-layer multi-mode flexible pressure sensor.

Description

Method for constructing flexible pressure sensor by direct-writing printing micro-nano depression template

Technical Field

The invention relates to the field of pressure sensors, and in particular to a method for bionic construction of a flexible pressure sensor using a direct-writing printing micro-nano recessed template.

Background technique

In recent years, flexible pressure sensors have played an important role in the fields of human-machine interface interaction such as wearable devices, life medicine, smart cities, electronic skin and motion detection due to their good mechanical flexibility and excellent pressure sensing performance. In order to meet the requirements of flexible pressure sensors for ultra-sensitive pressure sensing such as accurate capture of pressure signals, multi-dimensional perception response, and fast and stable output, it is necessary to conduct systematic research from aspects such as material selection, structural design, and processing technology. Among them, the micro-nanostructure flexible electrode determines the specific surface area, deformable space, and deformation capacity of the sensing area when subjected to pressure, which has an important influence on the pressure sensing performance of the flexible pressure sensor. Existing micro-nanostructure processing methods include replicating with natural micro-nano protrusion structures, self-assembly templates, masks, and etching. However, these methods have defects such as random shape and distribution of micro-nanostructures, high requirements for equipment accuracy and process, and it is difficult to achieve the controllable construction of micro-nano protrusion structure flexible electrodes, which limits the preparation of ultra-sensitive flexible pressure sensors.

Direct writing printing has attracted wide attention as a method for processing micro-nano structures. Compared with other methods for manufacturing micro-nano structures, direct writing printing is to disperse or dissolve functional materials (nanoparticles, polymers, liquids, etc.) in a solvent to make ink, and use automated equipment to control the direct writing printing needle to squeeze out ink droplets. After the ink droplets come into contact with the substrate, they will break and deposit on the substrate surface, thus forming the required patterned micro-nano structures. There is no need for processes such as masks and exposure etching, which saves costs and reduces pollution. At the same time, it also has the advantages of flexibility, rapidity, large-area preparation, strong environmental adaptability, and adaptability to different substrates.

Therefore, using direct writing printing technology to prepare controllable micro-nano concave structures and then constructing micro-nano convex structure flexible electrodes is of great significance for realizing ultra-sensitive multi-level and multi-mode flexible pressure sensors.

Summary of the invention

In order to address the deficiencies of the above-mentioned prior art, the purpose of the present invention is to provide a method for directly writing and printing micro-nano recessed templates to bionically construct flexible pressure sensors. The prepared sensor is an ultra-sensitive multi-level and multi-mode flexible pressure sensor, which can utilize direct writing and printing to print controllable micro-nano recessed structures on the surface of a viscoelastic substrate, and then construct a flexible electrode with a micro-nano protruding structure, thereby improving the performance of the sensor and enabling the preparation of ultra-sensitive multi-level and multi-mode flexible pressure sensors.

Specifically, the present invention provides a method for directly writing and printing a micro-nano depression template to bionically construct a flexible pressure sensor, which comprises the following steps:

S1. Preparing a support material base: cutting, cleaning and drying the support material to prepare a support material base;

S2, preparing a viscoelastic fluid mixture: mixing a prepolymer with a curing agent to obtain a viscoelastic fluid mixture;

S3, pre-curing: spin coating the viscoelastic fluid mixture on the support material substrate and pre-curing to obtain a viscoelastic substrate;

S4, setting printing parameters for printing: placing the viscoelastic substrate pre-cured in step S3 on the operating base of the dispensing machine, loading the nanoparticle ink into a syringe matched with the dispensing machine and connecting it to the dispensing machine, adjusting the distance between the needle and the viscoelastic substrate and the spacing of the ink droplet array during ink discharge, curing the printed sample, and then physically washing the cured sample to obtain a micro-nano recessed structure template;

S5, modification treatment: using air plasma to perform grafting modification on the micro-nano recessed structure template obtained in step S4, and performing silanization treatment on the surface by using a vapor deposition method;

S6, curing: pouring the viscoelastic fluid mixture prepared in step S2 onto the micro-nano recessed structure template processed in step S5, and peeling off after curing to obtain a micro-nano protruding structure substrate;

S7, preparing a flexible electrode using the micro-nano protrusion structure substrate obtained in step S6;

S8. Preparation of an ultra-sensitive multi-level multi-mode flexible pressure sensor: stack two flexible electrodes with micro-nano protrusion structures face to face, so that the micro-nano protrusion structure of the flexible electrode with the same structure is opposite to the gap of the protrusion structure of the other flexible electrode to form an interlocking structure, thereby obtaining an ultra-sensitive multi-level multi-mode flexible pressure sensor.

Preferably, in step S1, the supporting material is one of polyethylene terephthalate, polyimide, silicon wafer, glass or metal plate.

Preferably, the prepolymer in step S2 has viscoelasticity, and the prepolymer is one of polydimethylsiloxane, epoxy resin, thermoplastic polyurethane or natural rubber.

Preferably, the pre-curing method in step S3 includes thermal curing and light curing.

Preferably, in step S4, nanoparticle ink is used for direct printing on the surface of a viscoelastic substrate. A depression will occur in the area of the viscoelastic substrate surface that is contacted by the ink droplet. The nanoparticles in the ink droplet will form a dynamic extrusion assembly in the depression area as the solvent evaporates, thereby depositing to form a spherical micro-nano structure embedded in the substrate surface; when the viscoelastic substrate is solidified, the deposited spherical micro-nano structure is removed by physical washing to form a micro-nano depression structure on the film surface.

Preferably, the curing method in step S6 includes thermal curing and light curing.

Preferably, the method for preparing the flexible electrode in step S7 is to use a flexible substrate material for replication and then deposit a conductive material on its surface to realize a flexible electrode with a micro-nano protrusion structure, and the flexible electrode with a micro-nano protrusion structure is directly obtained by compounding the conductive material with the flexible substrate material and then replicating it.

Preferably, in step S8, the flexible pressure sensor comprises a capacitive pressure sensor, a piezoresistive pressure sensor or a piezoelectric pressure sensor.

Compared with the prior art, the present invention has the following beneficial effects:

(1) The present invention uses direct writing to print nanoparticle ink on the surface of a viscoelastic substrate to prepare a micro-nano recessed structure template. By controlling the pre-curing degree of the viscoelastic substrate and the printing conditions, the morphology, size and spacing of the micro-nano recessed structure are regulated. The corresponding micro-nano protruding structure flexible substrate is obtained by replicating the micro-nano recessed structure, and a micro-nano protruding structure flexible electrode with excellent mechanical and electrical properties is constructed by combining conductive materials. According to the working principle of the flexible pressure sensor, the flexible electrodes of the micro-nano protruding structure are stacked to prepare a flexible pressure sensor to achieve ultra-sensitive pressure sensing performance.

(2) The surface microstructure of the sensor electrode of the present invention can respond quickly to tiny pressures and exhibit good sensing performance within a wide pressure range, thus having good application prospects in sports tracking, health monitoring, etc.

BRIEF DESCRIPTION OF THE DRAWINGS

Figures 1a and 1b are schematic diagrams of a process for directly writing and printing micro-nano depression templates to bionically construct an ultra-sensitive multi-level multi-mode flexible pressure sensor; wherein Figure 1a is a schematic diagram of the process, and Figure 1b is a specific schematic diagram of the preparation method;

FIG2 is a schematic diagram of the deposition behavior of direct-writing nanoparticle ink droplets on the surface of a viscoelastic substrate and a schematic diagram of the morphology control of micro-nano concave structures;

FIG3 is a schematic diagram of microstructure arrays with different morphologies;

FIG4 is a schematic diagram of the sensing mechanism of the flexible pressure sensor;

Fig. 5a-Fig. 5l are optical microscope images of micro-nano recessed structures obtained by setting different printing intervals and different needle diameters and three-dimensional morphology images obtained by scanning with a step meter, wherein Fig. 5a, Fig. 5b, Fig. 5c, Fig. 5g, Fig. 5h, and Fig. 5i are optical microscope images respectively, and Fig. 5d, Fig. 5e, Fig. 5f, Fig. 5j, Fig. 5k, and Fig. 5l are corresponding three-dimensional morphology images;

6a to 6l are respectively optical microscope images of the micro-nano protrusion structure corresponding to FIG. 5a to FIG. 5l and three-dimensional morphology images of the micro-nano protrusion structure obtained by scanning with a step profiler;

Figures 7a-7f are schematic diagrams of the performance study of the flexible pressure sensor, wherein Figures 7a, 7b, and 7c are responses of sensors with different spacings under 1g (a), 5g (b), and 10g (c) weight loading/unloading conditions; Figure 7d is the response recovery time of the sensor; Figure 7e is the relative resistance change of the sensor with or without micro-nanostructure to the applied pressure; Figure 7f is a study of the durability and stability of the sensor;

FIG8 shows the application research of the flexible pressure sensor, where parts a, b, c, and d are breathing monitoring, sound vibration, pulse vibration, and wrist bending test, respectively.

Detailed ways

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Specifically, the present invention provides a method for directly writing and printing a micro-nano depression template to bionically construct a flexible pressure sensor, which comprises the following steps:

S1. Preparing a support material base: cutting, cleaning and drying the support material to prepare a support material base.

S2, preparing a viscoelastic fluid mixture: mixing a prepolymer with a curing agent to obtain a viscoelastic fluid mixture. In step S2, the prepolymer has viscoelasticity and includes polydimethylsiloxane, epoxy resin, thermoplastic polyurethane, and natural rubber.

S3, pre-curing: spin-coating the viscoelastic fluid mixture on the support material substrate and pre-curing to obtain a viscoelastic substrate. The pre-curing method in this step includes thermal curing and light curing.

S4, set printing parameters for printing: place the viscoelastic substrate pre-cured in step S3 on the operating base of the dispensing machine, load the nanoparticle ink into the syringe that cooperates with the dispensing machine and connect it to the dispensing machine, adjust the distance between the needle and the viscoelastic substrate when dispensing ink, the spacing of the ink droplet array, solidify the printed sample, and then physically rinse the solidified sample to obtain a micro-nano recessed structure template. In this step, nanoparticle ink is used for direct writing printing on the surface of the viscoelastic substrate. A recess will occur in the viscoelastic substrate surface area where the ink droplet contacts. The nanoparticles in the ink droplet will form a dynamic extrusion assembly in the recessed area as the solvent evaporates, thereby depositing to form a spherical micro-nano structure, which is embedded in the substrate surface. After the viscoelastic substrate is solidified, the deposited spherical micro-nano structure is removed by physical rinsing to form a micro-nano recessed structure on the film surface.

S5, modification treatment: the micro-nano recessed structure template obtained in step S4 is subjected to grafting modification by air plasma, and the surface is subjected to silanization treatment by vapor deposition method.

S6, curing: pouring the viscoelastic fluid mixture prepared in step S2 onto the micro-nano recessed structure template processed in step S5, and peeling off after curing to obtain a micro-nano protruding structure substrate. The curing method includes thermal curing and light curing.

S7, using the micro-nano protrusion structure substrate obtained in step S6 to prepare a flexible electrode. The method of preparing the flexible electrode includes using a flexible substrate material to replicate and then depositing a conductive material on its surface to realize a micro-nano protrusion structure flexible electrode, and directly obtaining a micro-nano protrusion structure flexible electrode by compounding the conductive material with the flexible substrate material and then replicating.

S8. Prepare an ultra-sensitive multi-level multi-mode flexible pressure sensor: stack two flexible electrodes with micro-nano convex structures face to face, so that the micro-nano convex structure of the flexible electrode with the same structure is opposite to the gap of the convex structure of the other flexible electrode, so that the two adjacent flexible electrodes form an interlocking structure, and obtain an ultra-sensitive multi-level multi-mode flexible pressure sensor. The prepared flexible pressure sensors include capacitive pressure, piezoresistive, and piezoelectric.

Specific embodiment 1

This embodiment provides a method for directly printing a micro-nano recessed template to construct a flexible pressure sensor by biomimetic construction, as shown in Figures 1a and 1b, and directly printing nanoparticle ink on the surface of a viscoelastic substrate to regulate the morphology, spacing and size of the micro-nano recessed structure, as shown in Figure 2. The corresponding micro-nano protruding structure flexible substrate is obtained by replicating the micro-nano recessed structure, and a micro-nano protruding structure flexible electrode with excellent mechanical and electrical properties is constructed in combination with a conductive material, as shown in Figure 3. According to the working principle of the flexible pressure sensor, a flexible pressure sensor is prepared by stacking a micro-nano protruding structure flexible electrode to achieve ultra-sensitive pressure sensing performance. The pressure applied to the sensor can cause the deformation of the micro-nano protruding structure on the surface of the flexible electrode, thereby inducing a rapid change in the contact area and actual channel width of the two electrodes, changing the contact resistance of the conductive layer, and realizing the sensor's detection of tiny pressures, as shown in Figure 4. This method has the advantages of large area, flexibility, large-scale preparation, low cost, and green environmental protection.

Specific embodiment 2

This embodiment provides a method for directly writing and printing a micro-nano depression template to bionically construct a flexible pressure sensor, the method comprising:

S1. Preparing a support material base: cutting, cleaning and drying the support material to prepare a support material base.

S2. Preparing a viscoelastic fluid mixture: mixing a prepolymer with a curing agent to obtain a viscoelastic fluid mixture.

S3, pre-curing: spin coating the viscoelastic fluid mixture on the support material substrate and pre-curing it to obtain a pre-cured viscoelastic substrate.

In this embodiment, polyethylene terephthalate (PET) is cut into 3cm×3cm and placed in an ethanol solution for ultrasonic cleaning. After cleaning, it is placed in a 60°C oven for drying. Weigh the polydimethylsiloxane (PDMS) precursor and curing agent in a beaker, the mass ratio of the precursor to the curing agent is 10:1, stir evenly and evacuate to remove bubbles. Spin coat the prepared PDMS on the PET surface with a spin coating thickness of 200μm. After spin coating, place it in a vacuum drying oven for pre-curing at 70°C for 5min to obtain a viscoelastic substrate.

S4, set printing parameters for printing: place the pre-cured viscoelastic substrate on the operating base of the dispensing machine, load the nanoparticle ink into the syringe that cooperates with the dispensing machine and connect it to the dispensing machine, adjust the distance between the needle and the viscoelastic substrate when the ink is discharged, and the distance is adjusted as needed. The spacing of the ink droplet array is set as needed, preferably between 100-300μm, and the needle diameter is preferably set between 100-200μm. The printed sample is cured, and then the cured sample is physically rinsed to obtain a micro-nano recessed structure template. During the preparation process, nanoparticle ink is used for direct writing printing on the surface of the viscoelastic substrate. The viscoelastic substrate surface area contacted by the ink droplet will be depressed. The nanoparticles in the ink droplet will form a dynamic extrusion assembly in the depressed area as the solvent evaporates, thereby depositing to form a spherical micro-nano structure, embedded in the substrate surface. After the viscoelastic substrate is cured, the deposited spherical micro-nano structure is removed by physical rinsing to form a micro-nano recessed structure on the surface of the film.

S5. Modification treatment: The micro-nano recessed structure template is grafted and modified by air plasma, and the surface is silanized by vapor deposition method.

S6, solidification: pouring the viscoelastic fluid mixture prepared in step S2 onto the micro-nano recessed structure template processed in step S5, and peeling off after solidification to obtain a micro-nano protruding structure substrate.

S7. Prepare a flexible electrode. The specific process is: use a flexible substrate material to replicate and then deposit a conductive material on its surface to realize a flexible electrode with a micro-nano protrusion structure. The flexible electrode with a micro-nano protrusion structure is directly obtained by compounding the conductive material with the flexible substrate material and then replicating.

S8. Preparation of an ultra-sensitive multi-level multi-mode flexible pressure sensor: stack two flexible electrodes with micro-nano protrusion structures face to face, so that the micro-nano protrusion structure of the flexible electrode with the same structure is opposite to the gap of the protrusion structure of the other flexible electrode to form an interlocking structure, thereby obtaining an ultra-sensitive multi-level multi-mode flexible pressure sensor.

Figures 5a-5l are optical microscope images of micro-nano recessed structures with different printing spacings (three groups, a: 300μm, b: 200μm, c: 100μm) and different needle diameters (three groups, g: 100μm, h: 150μm, i: 200μm) in Example 2, and three-dimensional morphology images of the micro-nano recessed structures obtained by scanning with a step meter. Figures 6a-6l are optical microscope images of micro-nano protruding structures corresponding to Figures 5a-5l, and three-dimensional morphology images of the micro-nano protruding structures obtained by scanning with a step meter. Figures 7a-7f are performance studies of flexible pressure sensors, wherein Figures 7a, 7b, and 7c are responses of sensors with different spacings under 1g (a), 5g (b), and 10g (c) weight loading/unloading conditions; Figure 7d is the response recovery time of the sensor; Figure 7e is the relative resistance change of the sensor with or without micro-nano structures to applied pressure; and Figure 7f is a study of the durability and stability of the sensor. FIG8 shows the application research of the flexible pressure sensor, where a), b), c), and d) are breathing monitoring, sound vibration, pulse vibration, and wrist bending test, respectively.

The embodiments described above are only descriptions of the preferred implementation modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims (8)

1. A method for constructing a flexible pressure sensor by directly writing and printing micro-nano concave templates in a bionic mode is characterized by comprising the following steps of: which comprises the following steps:

s1, preparing a support material substrate: cutting, cleaning and drying the support material to prepare a support material substrate;

S2, preparing a viscoelastic fluid mixture: mixing the prepolymer with a curing agent to obtain a viscoelastic fluid mixture;

S3, pre-curing: spin coating a viscoelastic fluid mixture on a support material substrate and pre-curing to obtain a viscoelastic substrate;

S4, setting printing parameters to print: placing the pre-cured viscoelastic substrate in the step S3 on an operation base of a dispensing machine, filling nanoparticle ink into a needle cylinder matched with the dispensing machine and connecting the nanoparticle ink with the dispensing machine, adjusting the distance between a needle head and the viscoelastic substrate and the distance between ink drop matrixes during ink discharge, curing a printed sample, and then physically flushing the cured sample to obtain a micro-nano concave structure template;

s5, modification treatment: performing grafting modification on the micro-nano concave structure template obtained in the step S4 by adopting air plasma, and performing silanization treatment on the surface by utilizing a vapor deposition method;

s6, curing: pouring the viscoelastic fluid mixture configured in the step S2 on the micro-nano concave structure template processed in the step S5, and stripping after solidification to obtain a micro-nano convex structure substrate;

s7, preparing a flexible electrode by utilizing the micro-nano bulge structure substrate obtained in the step S6;

S8, preparing an ultrasensitive multi-layer multi-mode flexible pressure sensor: and stacking the two flexible electrodes with the micro-nano bulge structures face to face, so that the micro-nano bulge structures of the flexible electrodes with the same structure are opposite to the gaps of the bulge structures of the other flexible electrode to form an interlocking structure, and thus the ultra-sensitive multi-layer multi-mode flexible pressure sensor is obtained.

2. The method for constructing the flexible pressure sensor by using the direct-writing printing micro-nano concave template in a bionic mode, which is characterized by comprising the following steps of: in the step S1, the supporting material is one of polyethylene terephthalate, polyimide, silicon wafer, glass or metal plate.

3. The method for constructing the flexible pressure sensor by using the direct-writing printing micro-nano concave template in a bionic mode, which is characterized by comprising the following steps of: in the step S2, the prepolymer has viscoelasticity, and is one of polydimethylsiloxane, epoxy resin, thermoplastic polyurethane or natural rubber.

4. The method for constructing the flexible pressure sensor by using the direct-writing printing micro-nano concave template in a bionic mode, which is characterized by comprising the following steps of: the pre-curing method in step S3 includes thermal curing and photo-curing.

5. The method for constructing the flexible pressure sensor by using the direct-writing printing micro-nano concave template in a bionic mode, which is characterized by comprising the following steps of: in the step S4, nanoparticle ink is adopted to directly write and print on the surface of the viscoelastic substrate, the surface area of the viscoelastic substrate contacted by ink drops is recessed, the nanoparticles in the ink drops form dynamic extrusion assembly along with the volatilization of a solvent in the recessed area, so that spherical micro-nano structures are formed by deposition and embedded on the surface of the substrate; and after the viscoelastic substrate is solidified, removing the deposited spherical micro-nano structure by a physical flushing mode, and forming a micro-nano concave structure on the surface of the film.

6. The method for constructing the flexible pressure sensor by using the direct-writing printing micro-nano concave template in a bionic mode, which is characterized by comprising the following steps of: the curing method in step S6 includes thermal curing and photo curing.

7. The method for constructing the flexible pressure sensor by using the direct-writing printing micro-nano concave template in a bionic mode, which is characterized by comprising the following steps of: the flexible electrode is prepared in the step S7 by using a flexible substrate material to copy and then depositing a conductive material on the surface of the flexible substrate material to realize the flexible electrode with the micro-nano bulge structure, and the flexible electrode with the micro-nano bulge structure is directly obtained by compounding the conductive material and the flexible substrate material and then copying.

8. The method for constructing the flexible pressure sensor by using the direct-writing printing micro-nano concave template in a bionic mode, which is characterized by comprising the following steps of: the flexible pressure sensor in step S8 comprises a capacitive pressure sensor, a piezoresistive pressure sensor or a piezoelectric pressure sensor.