阅读说明：本技术 基于MXene仿生皮肤结构的高灵敏度柔性压阻传感器 (High-sensitivity flexible piezoresistive sensor based on MXene bionic skin structure ) 是由 马亚楠 于 2019-10-18 设计创作，主要内容包括：本发明公开了一种基于MXene仿生皮肤结构的高灵敏度柔性压阻传感器,包括柔性叉指电极层、MXene基硅胶仿生层和封装层；其中：MXene基硅胶仿生层是通过硅胶印模砂纸,得到具有仿生皮肤结构的薄膜,然后涂覆在仿生膜上制备得到；所述柔性叉指电极层是通过喷墨打印和磁控溅射研制得到,且MXene基硅胶仿生层与电极区直接接触而形成回路,所述封装材料优选为聚乙烯膜。本发明的柔性压敏传感器具有极高的灵敏度、低的检测极限、快的响应时间和良好的稳定性,在电子皮肤、可穿戴电子器件等实际应用中表现出很大的应用潜力。本发明的传感器解决了现有MXene基压阻传感器制备工艺复杂、且很难同时具备高的灵敏度和稳定性的问题。(The invention discloses a high-sensitivity flexible piezoresistive sensor based on an MXene bionic skin structure, which comprises a flexible interdigital electrode layer, an MXene silicon adhesive bionic layer and a packaging layer; wherein: the MXene silica gel bionic layer is prepared by obtaining a film with a bionic skin structure through silica gel impression sand paper and then coating the film on a bionic film; the flexible interdigital electrode layer is developed through ink-jet printing and magnetron sputtering, the MXene silicon adhesive bionic layer is in direct contact with the electrode area to form a loop, and the packaging material is preferably a polyethylene film. The flexible pressure-sensitive sensor has extremely high sensitivity, low detection limit, quick response time and good stability, and has great application potential in practical application of electronic skins, wearable electronic devices and the like. The sensor solves the problems that the existing MXene-based piezoresistive sensor is complex in preparation process and difficult to have high sensitivity and stability.)

1. A high-sensitivity flexible piezoresistive sensor based on an MXene bionic skin structure is characterized in that: the flexible interdigital electrode layer, the MXene silica gel bionic layer and the packaging layer are sequentially stacked from bottom to top.

2. The MXene biomimetic skin structure-based high-sensitivity flexible piezoresistive sensor according to claim 1, characterized in that: the MXene-based silica gel bionic material is prepared by obtaining a bionic film with a bionic skin structure through silica gel impression sand paper and then coating MXene colloidal solution on the bionic film.

3. The MXene biomimetic skin structure-based high-sensitivity flexible piezoresistive sensor according to claim 1, characterized in that: the flexible interdigital electrode layer is prepared through ink-jet printing and magnetron sputtering in sequence, and the MXene silicon adhesive bionic layer directly contacts with the electrode area to form a loop.

4. The MXene biomimetic skin structure-based high-sensitivity flexible piezoresistive sensor according to claim 1, characterized in that: the encapsulating material is preferably a polyethylene film.

5. the MXene biomimetic skin structure-based high-sensitivity flexible piezoresistive sensor according to claim 1, characterized in that: the silica gel is any one of polydimethylsiloxane and polyurethane.

6. the MXene biomimetic skin structure-based high-sensitivity flexible piezoresistive sensor according to claim 1, characterized in that: the flexible interdigital electrode substrate is any one of a polyethylene terephthalate film, a polyimide film or a polydimethylsiloxane film.

7. the method for preparing the high-sensitivity flexible piezoresistive sensor based on the MXene bionic skin structure, according to claim 1, is characterized in that: the method comprises the following steps:

s1: etching, centrifuging and washing the MAX phase precursor in hydrofluoric acid etching solution, and then carrying out ultrasonic treatment and centrifugation in an ice bath under the protection of inert atmosphere to obtain MXene colloidal solution;

S2: placing a silica gel solution impression on the surface of abrasive paper, standing in vacuum, drying, and slowly tearing off the obtained silica gel film with the impression abrasive paper structure to obtain a silica gel bionic layer;

S3: diluting the MXene colloidal solution obtained in the step S1, coating the diluted MXene colloidal solution on the bionic surface of the silica gel obtained in the step S2, and drying to obtain an MXene silica gel bionic layer;

s4: printing a flexible interdigital electrode pattern on a flexible substrate by an ink-jet printing technology, then carrying out magnetron sputtering on conductive metal, and carrying out ultrasonic cleaning to form a flexible interdigital electrode;

S5: and (4) fixing the MXene-based silica gel bionic layer obtained in the step (S3) on the flexible interdigital electrode obtained in the step (S4), then packaging and fixing the flexible interdigital electrode by adopting a packaging film, and leading the electrode by using a copper wire to obtain the MXene-based bionic piezoresistive sensor.

8. the method for preparing the high-sensitivity flexible piezoresistive sensor based on the MXene bionic skin structure according to claim 7, wherein the method comprises the following steps: the MAX phase precursor in step S1 is preferably Ti₃AlC₂The particle size is less than or equal to 38 mu m.

9. The method for preparing the high-sensitivity flexible piezoresistive sensor based on the MXene bionic skin structure according to claim 7, wherein the method comprises the following steps: the preferable choice of the dispersoid MXene in the MXene colloidal solution in the step S1 is Ti₃C₂T_xa nano-sheet layer, wherein the MXene sheet layer size is 200-2000 nm.

10. Use of an MXene biomimetic skin structure based high-sensitivity flexible piezoresistive sensor according to any of claims 1-6 or an MXene biomimetic skin structure based high-sensitivity flexible piezoresistive sensor prepared by the method according to any of claims 7-9, characterized in that: can be used in electronic skin and wearable electronic devices.

Technical Field

The invention belongs to the technical field of wearable electronics and new materials, particularly relates to a flexible piezoresistive sensor, and more particularly relates to a high-sensitivity flexible piezoresistive sensor based on a two-dimensional MXene material sand paper bionic skin structure, and a preparation method and application thereof.

Background

In recent years, a flexible pressure sensor has attracted considerable attention in the fields of the internet of things, the smart industry, and the like, as one of important components of smart devices, due to the characteristics of being bendable at will and comfortable to wear. According to different working principles, flexible pressure sensors are mainly classified into piezoresistive type, piezoelectric type and capacitive type. Compared with piezoelectric and capacitive pressure sensors, piezoresistive pressure sensors (piezoresistive sensors for short) have the advantages of simple preparation process, small volume, low energy consumption (only nW is needed for driving power), simple and accurate signal detection, stable performance and the like. In recent years, with the continuous progress and development of science and technology, higher requirements are put forward on the performance of piezoresistive sensors in the fields of medical diagnosis, internet of things, artificial intelligence and the like. At present, the core problem of piezoresistive sensor-related research is how to further improve the sensitivity of existing devices to meet practical requirements.

Research shows that the selection and quality of sensitive materials and the design and optimization of device geometric configuration are crucial to improving the sensitivity of piezoresistive sensors. At present, carbon materials represented by two-dimensional graphene and one-dimensional carbon nanotubes have abundant microstructures, excellent conductivity and strong mechanical strength, and are widely applied to the development of miniature flexible piezoresistive sensors. However, in practical applications, graphene and carbon nanotubes prepared by chemical vapor deposition have high requirements on equipment and are difficult to transfer, and piezoresistive sensors prepared from a single material have low sensitivity and a small dynamic range, which limits further applications of the piezoresistive sensors in sensors. The new two-dimensional transition metal carbide, nitride and carbonitride family MXene has the characteristics of low preparation cost, high yield, short period, good mechanical property and metal conductivity, high biocompatibility and adjustable microstructure, and is an ideal piezoresistive sensor sensitive material.

In recent years, researchers successfully construct three-dimensional MXene composite aerogel, MXene sponge piezoresistive sensors and MXene nano-network strain sensors, and the sensors have high sensitivity and stability. However, the MXene-based flexible piezoresistive sensor constructed by the existing geometric configuration is thick and poor in light transmission, and the wearability of the sensor is difficult to realize. In addition, the regulation rule of the contact resistance of the MXene sensitive material and the flexible substrate on the sensitivity of the piezoresistive sensor is also to be further researched.

the present application is particularly proposed based on the above-mentioned drawbacks of the prior art.

Disclosure of Invention

Aiming at the defects or improvement requirements of the prior art, the invention provides the high-sensitivity flexible piezoresistive sensor based on the MXene bionic skin structure, the bionic skin structure is obtained by impression sand paper, under the action of external micro force, point contact and line contact replace the surface contact of the traditional piezoresistive sensor, the conductive path is obviously increased, the resistance is sharply reduced, and thus, the pressure-sensitive sensor has extremely high sensitivity, low detection limit and quick response time; silica gel with good mechanical flexibility is used as a substrate material to endow the sensor with good stability, so that the MXene-based piezoresistive sensor has great application potential in practical applications such as electronic skins and wearable electronic devices.

In order to achieve the above object, according to an aspect of the present invention, there is provided a high-sensitivity flexible piezoresistive sensor based on an MXene biomimetic skin structure, including a flexible interdigital electrode layer, an MXene silica gel biomimetic layer, and an encapsulation layer, which are sequentially stacked from bottom to top.

Further, according to the technical scheme, the MXene silica gel bionic material is prepared by obtaining a bionic film with a bionic skin structure through silica gel impression sand paper and then coating MXene colloidal solution on the bionic film.

Further, according to the technical scheme, the flexible interdigital electrode layer is prepared through ink-jet printing and magnetron sputtering in sequence, and the MXene silicon adhesive bionic layer directly contacts with the electrode area to form a loop.

Further, in the above technical solution, the sealing material is preferably a polyethylene film.

Further, according to the above technical scheme, the silica gel is any one of high polymer such as Polydimethylsiloxane (PDMS) and Polyurethane (PU).

Further, according to the above technical solution, the flexible interdigital electrode substrate may be any one of a polyethylene terephthalate film, a polyimide film, a polydimethylsiloxane film, or the like, and is preferably a polyimide film.

Further, according to the technical scheme, the flexible silica gel bionic layer can be obtained by stamping sand paper with different meshes (400 meshes and 5000 meshes).

in a second aspect of the present invention, a method for preparing a high-sensitivity flexible piezoresistive sensor based on an MXene biomimetic skin structure is provided, where the method includes the following steps:

S1: etching, centrifuging and washing the MAX phase precursor in hydrofluoric acid etching solution, and then carrying out ultrasonic treatment and centrifugation in an ice bath under the protection of inert atmosphere to obtain MXene colloidal solution;

S2: placing a silica gel solution impression on the surface of abrasive paper, standing in vacuum, drying, and slowly tearing off the obtained silica gel film with the impression abrasive paper structure to obtain a silica gel bionic layer;

S3: diluting the MXene colloidal solution obtained in the step S1, coating the diluted MXene colloidal solution on the bionic surface of the silica gel obtained in the step S2, and drying to obtain an MXene silica gel bionic layer;

s4: printing a flexible interdigital electrode pattern on a flexible substrate by an ink-jet printing technology, then carrying out magnetron sputtering on conductive metal, and carrying out ultrasonic cleaning to form a flexible interdigital electrode;

S5: and (4) fixing the MXene-based silica gel bionic layer obtained in the step (S3) on the flexible interdigital electrode obtained in the step (S4), then packaging and fixing the MXene-based silica gel bionic layer by adopting a packaging film, and leading the electrode by using a copper wire to obtain the MXene-based bionic piezoresistive sensor.

Further, in the above technical solution, in the MAX phase precursor in step S1, M is a transition metal, a is mainly a group iii element or a group iv element, and X is a group C element or a group N element. The MAX phase precursor is preferably Ti₃AlC₂Preferably with a particle size of 38 μm or less, in particular the commercially available MAX phase precursor Ti₃AlC₂grinding, and sieving with 400 mesh sieve.

Further, in the above technical solution, MXene in the MXene colloidal solution in step S1 is preferably Ti₃C₂T_xA nanosheet, the MXene lamella having a size (lateral dimension) of 200-.

Further, in the above technical solution, the inert atmosphere in step S1 is preferably an argon atmosphere.

Further, in the above technical solution, the time of the vacuum standing in step S2 is preferably 10-20min, and the purpose of the vacuum standing is to remove bubbles.

Further, in the above technical solution, the drying temperature and time in step S2 are 60-90 ℃ and 0.5-1h, respectively.

Further, in the technical scheme, in order to improve the binding capacity of the silica gel biomimetic material obtained in the step S2 with the sensitive material MXene, a plasma cleaning machine can be used for processing in advance to obtain more hydrophilic groups; in the plasma treatment process, the introduced gas is oxygen or air, and the treatment time is 2-6 min.

Further, in the above technical solution, the concentration of the diluted MXene colloidal solution in the step S1 is 1-10 mg/ml.

Further, in the above technical solution, the coating in step S3 is preferably performed by spray gun, and the diameter of the spray gun head is 0.2-0.5 mm.

Further, in the above technical solution, in step S4, the conductive metal is preferably Ni or Au, where: the power and time of the Ni in magnetron sputtering are respectively 80-200W and 30-90s, the power and time of the Au sputtering are respectively 100-220W and 10-30 s.

the third aspect of the invention is to provide an application of the high-sensitivity flexible piezoresistive sensor based on the MXene bionic skin structure, which can be used in electronic skin and wearable electronic devices.

in general, compared with the prior art, the above technical solution contemplated by the present invention can achieve the following beneficial effects:

(1) Compared with the traditional pressure sensor preparation process, the method of the invention adopts the impression sand paper and the active material spraying method, has the advantages of simplicity, high efficiency, low cost and the like, and is expected to realize mass production. The bionic skin structure obtained by the impression sand paper has the advantages that under the action of external micro-force, point contact and line contact replace surface contact, a conductive path is remarkably increased, extremely high sensitivity is shown, physiological signals of a human body such as pulse fluctuation can be clearly distinguished, and the bionic skin structure has great potential in practical application such as electronic skin and wearable electronic devices.

(2) In the technical scheme of the invention, the adopted silica gel bionic layer has good flexibility, can be well contacted with the electrode, and is easy to be adhered to the uneven skin of a human body uniformly, so that the physical signals from the human body can be better monitored or the stimulation from the outside can be better detected in practical application.

(3) The sensitive layer obtained by spraying MXene colloidal solution through the flexible silica gel impression sand paper shows extremely high sensitivity (224.15 kPa)^-1) And low detection limit, low working voltage, fast response time and good circulation stability, under the action of small external force, the bionic skin structure deforms, the conductive path is increased, and the resistance is reduced.

(4) the MXene nano material prepared by the chemical etching method has good hydrophilicity, higher conductivity and excellent mechanical strength.

(5) The sensor solves the problems that the existing MXene-based piezoresistive sensor is complex in preparation process and difficult to have high sensitivity and stability.

(6) MXene as a novel two-dimensional material has the advantages of large specific surface area, good water solubility, good conductivity and the like, is very suitable for being used as a sensitive material, and the regulation and control rule of MXene nano material characteristics and geometric configuration on sensitivity is urgently needed to be researched. The technical scheme of the invention provides a method for researching the regulation and control rule of the contact resistance of the MXene sensitive material and the flexible substrate on the sensitivity of the piezoresistive sensor.

Drawings

FIG. 1 is a flow chart of a process for manufacturing a high-sensitivity flexible piezoresistive sensor based on a two-dimensional MXene material sand paper bionic skin structure in the implementation of the present invention;

FIG. 2 is a physical diagram (a) of an MXene-based silica gel bionic layer and SEM diagrams (b-f) of MXene-based silica gel bionic layers with different mesh numbers of stamps; (b)400 meshes; (c)800 meshes; (d)2000 mesh; (e)3000 meshes; (f)5000 meshes;

FIG. 3 is a diagram illustrating the electrical response test of MXene-based bionic piezoresistive sensor (a) prepared in example 2 of the present invention to pressure; (b) current-time and pressure-time tests were performed; (c) testing the response time of the device; (d) testing the stability of the device;

FIG. 4 is a diagram of the MXene-based bionic piezoresistive sensor manufactured in example 2 for monitoring the response of a device to a small pressure in practical application test (a); (b) testing finger contact; (c) testing the bending of the wrist; (d) and (5) testing wrist pulse.

Detailed Description

in order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

Fig. 1 is a flow chart of a manufacturing process of a high-sensitivity flexible piezoresistive sensor with a two-dimensional MXene material sandpaper bionic skin structure in embodiment 1 of the present invention. As shown in fig. 1, the process comprises the following steps:

(1) etching MAX phase by a chemical solution method, and performing centrifugal cleaning and low-temperature ultrasound to prepare MXene nanosheets;

(2) Preparing a silica gel solution and preparing a silica gel film with a stamp sand paper structure;

(3) Preparing an MXene silica gel bionic layer;

(4) preparing a flexible interdigital electrode;

(5) And assembling the MXene-based bionic piezoresistive sensor.