WO2019113731A1

WO2019113731A1 - Flexible pressure sensor and method for preparing same

Info

Publication number: WO2019113731A1
Application number: PCT/CN2017/115434
Authority: WO
Inventors: 李晖; 张劲杰; 王磊
Original assignee: 中国科学院深圳先进技术研究院
Priority date: 2017-12-11
Filing date: 2017-12-11
Publication date: 2019-06-20

Abstract

A method for preparing a flexible pressure sensor, comprising: preparing a PDMS membrane of a conical microarray structure; pretreating a carbon nanotube powder; preparing a prefabricated carbon nanotube membrane; stripping a carbon nanotube membrane from the prefabricated carbon nanotube membrane; air-drying the carbon nanotube membrane; placing the carbon nanotube membrane on the PDMS membrane of the conical microarray structure, and heating at a temperature of 180-220°C for 20-40 minutes; preparing a semi-cured smooth PDMS membrane; and attaching the semi-cured smooth PDMS membrane on the carbon nanotube membrane and the PDMS membrane of the conical microarray structure, and heating at a temperature of 70-90°C for 20-30 minutes, thereby obtaining the flexible pressure sensor. Also provided is the flexible pressure sensor. The flexible pressure sensor is high in precision, short in response time, and would not be easily interfered.

Description

Flexible pressure sensor and preparation method thereof

Technical field

The invention belongs to the technical field of flexible pressure sensors, and in particular relates to a flexible pressure sensor and a preparation method thereof.

Background technique

In recent years, with the continuous development of the robot field, more and more people are paying attention to the research and development of the tactile sensing of robot hands. Flexible pressure sensors are not only necessary devices to promote the development of precision force feedback systems for medical devices and humanoid robots, but also important components for the next generation of wearable electronic devices for monitoring human physiological signals. In the actual use process, the sensor is required to be transparent, flexible, extended, and highly sensitive, especially in the working environment on the complex and irregular skin surface of the human body. With the development of flexible matrix materials, flexible pressure sensors that meet the above characteristics have emerged on this basis.

As the application requirements in the information age become higher and higher, the expected values and idealized requirements for various performance parameters such as the range, accuracy, and stability of the measured information are gradually increased. The sensor system of wearable devices has gradually shown its limitations in some applications, including the current lack of flexibility of the sensor, low precision, small sensing range, lag in response, and easy interference with human physiological signal noise, resulting in uncomfortable wear. , signal acquisition is fuzzy and incomplete, inaccurate and so on.

The current flexible pressure sensor preparation methods mainly include the following:

Polydimethylsiloxane (PDMS) was coated on silk, PDMS obtained a pattern opposite to silk grain; carbon nanotube film was obtained by leakage method; carbon nanotube film and patterned PDMS were attached After heating, the film is coated with a smooth PDMS film on the other side of the carbon nanotube film. Finally, electrodes are added on both sides of the film to form a sensor. The pressure sensor can sense a pressure of 0.1 at least, and the response recovery time is in the millisecond range. within.

Add carbon nanotubes to N-methylpyrrolidone for 30 minutes, centrifuge for 30 minutes; then at 200 At a degree Celsius, it was sprayed on the surface of the silicon wafer to form an electrode, and a polyurethane elastomer solution was spin-coated on the electrode, and then the electrode was transferred onto a polyurethane substrate; the carbon nanotube powder and the chloroform solution were ultrasonicated for 20 minutes, and then added to the poly- 3-hexylthiophene was ultrasonicated for 60 minutes, centrifuged for 20 minutes, and the treated carbon nanotubes were mixed with polyurethane, added to a chloroform solution, and spin-coated on a PDMS mold having a pyramid structure to form a piezoresistive polymer; Laminated on top of the piezoresistive pyramid and heated at 60 ° C for 5 minutes to ensure good bonding, then the carbon nanotube electrode / piezoresistive polymer was removed from the mold, and silver nanowires were sprayed into the embedded PDMS to form a pressure sensor. Since the structure of the pyramid reduces the effective modulus and concentrates the electric field, the piezoresistive characteristics with respect to the unstructured film are improved, and the sensitivity of the sensor is improved.

Mix EcoFlex's A and B in a 1:1 ratio, defoam, spin-coat on a 3D mold prepared by 3D printing or photolithography, let stand for 4 hours to completely dry the EcoFlex, tear off the film; Spin-coated on a smooth substrate at 1100 rpm to obtain an Ecoflex film with a thickness of 1 mm, heated in a 60-degree drying oven for 40 seconds; another patterned film with a pattern prepared thereon, at room temperature It was dried for several hours until it was completely dry; a gallium-indium alloy was injected into the channel of the two-layer film with a syringe, and both ends of the channel were sealed with EcoFlex. This method can obtain a flexible pressure sensor with a resolution of 1 KPa in the range of 0-100 KPa.

The PDMS solution containing the base prepolymer and the crosslinking agent (weight ratio 10:1) was coated on the glass piece and then defoamed, and the PDMS was heated at 120 degrees for 1 hour; the PDMS surface was treated with oxygen plasma to form a pro Water surface layer; graphene obtained by chemical vapor deposition was transferred to the PDMS surface; patterning was performed using photolithography and reactive ion etching; and then the two channels were vertically laminated under the guidance of the aligner mark. The flexible pressure sensor obtained by this method has a sensing range of 0-450 KPa, and a minimum pressure of 0.5 KPa can be sensed, and the response time is less than 0.2 s.

Although the above sensors can basically sense the externally applied pressure, there are still some shortcomings: the piezoresistive pressure sensor based on the silk grain microstructure has a small sensing range and is only suitable for sensing small pressure; based on a small size pyramid The micro-array structure of the pressure sensor has a small dynamic monitoring range and is only suitable for sensing static pressure; the microchannel-based pressure sensor has low sensing accuracy, low spatial resolution, and response lag; PDMS-based capacitors Pressure sensor is susceptible to noise Disturbance requires more complex circuitry to compensate or eliminate noise interference.

Summary of the invention

Based on this, it is necessary to provide a flexible pressure sensor with higher precision, shorter response time and less susceptible to interference, and a preparation method thereof.

A method for preparing a flexible pressure sensor, comprising:

The PDMS solution containing PDMS and cross-linking agent is coated on a mold having an array of conical groove structures, heated at 70-90 ° C for 30-60 minutes, left to cool to room temperature, and the PDMS film is separated from the mold. Obtaining a PDMS film having a conical microarray structure;

Adding carbon nanotube powder to a mixed solution of hydrogen chloride and hydrogen peroxide, and preheating at a temperature of 55-65 ° C for 3.5-4.5 hours;

The pretreated carbon nanotube powder is added to the dimethylformamide solution, vacuum leaking is performed by using a microporous filtration membrane, and a pre-formed carbon nanotube film is formed on the microporous filtration membrane;

The microporous filtration membrane formed with the pre-formed carbon nanotube film is obliquely inserted into deionized water, and the carbon nanotube film is peeled off from the pre-formed carbon nanotube film;

After the carbon nanotube film is air-dried, the carbon nanotube film is placed on the PDMS film of the conical microarray structure, and heated at a temperature of 180-220 ° C for 20-40 minutes;

The PDMS solution containing PDMS and a crosslinking agent is coated on a silicon wafer and heated at 70-90 ° C for 20-30 minutes, and left to cool to room temperature to obtain a semi-cured smooth PDMS film;

The semi-cured smooth PDMS film was attached to the carbon nanotube film and the PDMS film of a conical microarray structure, and heated at a temperature of 70-90 ° C for 20-30 minutes to obtain a sandwich-type flexible pressure sensor.

In one embodiment, the preparation method further comprises: respectively extracting electrodes from both sides of the intermediate layer of the sandwich structure of the flexible pressure sensor.

In one embodiment, the weight ratio of the PDMS to the crosslinker is from 8:1 to 10:1.

In one embodiment, the conical groove has a depth of 30 to 60 μm, and the conical surface The diameter is 30 to 60 μm.

In one embodiment, the PDMS film has a thickness of 150 to 250 μm.

In one embodiment, the volume ratio of hydrogen chloride to hydrogen peroxide is from 2:1 to 3:1.

In one embodiment, the pre-formed carbon nanotube film has a thickness of 100 to 300 μm, and the carbon nanotube film has a thickness of 40 to 60 nm.

A flexible pressure sensor obtained by the method as described above, the flexible pressure sensor comprising:

a PDMS film of a conical microarray structure;

a carbon nanotube film bonded to the surface of the PDMS film; and

A smooth PDMS film placed on the carbon nanotube layer.

In one embodiment, the PDMS film has a thickness of 150 to 250 μm, and the carbon nanotube film has a thickness of 40 to 60 nm.

In one embodiment, the flexible pressure sensor has electrodes on both sides of the sandwich structure intermediate layer.

In the above flexible pressure sensor and method, the conical array microstructure will not only shorten the response time of the sensor to external pressure to about 100 μs, but also improve the linearity of the sensor, and the minimum sensed pressure reaches 1 mN, based on Conical microarray structure PDMS substrate flexible pressure sensor has good softness, biocompatibility, non-toxic and other characteristics, has no side effects on the skin surface of human body or other organisms, and has good skin adhesion. The sensing part based on carbon nanotubes has high spatial resolution, high sensitivity and strong anti-noise ability. At the same time, the above flexible pressure sensor also has the characteristics of low power consumption. The above flexible pressure sensor has great application prospects in multi-field applications such as flexible wearable devices, artificial electronic skin, two-way force feedback of interventional medical robots, and soft body robots.

DRAWINGS

1 is a schematic flow chart of a method for preparing a flexible pressure sensor according to an embodiment;

2 is a cross-sectional structural view of a mold having an array of conical groove structures according to an embodiment;

3 is a schematic view showing the structure of a mold having an array of conical groove structures according to an embodiment;

4 is a schematic structural view of a flexible pressure sensor of an embodiment.

Detailed ways

A flexible pressure sensor and a preparation method thereof will be further described in detail below with reference to the embodiments and the accompanying drawings.

Referring to FIG. 1, a method for preparing a flexible pressure sensor according to an embodiment includes:

S110, coating a PDMS solution containing PDMS and a crosslinking agent on a mold having an array of conical groove structures (as shown in FIGS. 2 and 3), heating at 70-90 ° C for 30-60 minutes, and allowing to stand. After cooling to room temperature, the PDMS film was separated from the mold to obtain a PDMS film of a conical microarray structure.

The PDMS film of the conical microarray structure obtained by using the mold of the conical groove structure array is deformed very uniformly when subjected to external pressure, compared with the array having no shape structure or other shape, and the PDMS film of the conical microarray structure is deformed. Good linearity.

In one embodiment, the weight ratio of PDMS to crosslinker is from 8:1 to 10:1. Preferably, the weight ratio of PDMS to crosslinker is 10:1. The crosslinker used allows the PDMS to be cured.

In one embodiment, the conical groove has a depth of 30 to 60 μm, and the conical surface has a diameter of 30 to 60 μm. Preferably, the conical groove has a depth of 50 μm and the conical surface has a diameter of 50 μm.

In one embodiment, the PDMS film has a thickness of from 150 to 250 [mu]m. Preferably, the PDMS film has a thickness of 200 μm.

S120, adding carbon nanotube powder to a mixed solution of hydrogen chloride and hydrogen peroxide, and preheating at a temperature of 55-65 ° C for 3.5-4.5 hours.

The carbon nanotube powder is more dispersed by the above pretreatment, so that the carbon nanotube film obtained by the vacuum evacuation in the next step is more uniform.

In one embodiment, the volume ratio of hydrogen chloride to hydrogen peroxide is from 2:1 to 3:1. Preferably, the volume ratio of hydrogen chloride to hydrogen peroxide is 3:1.

S130, adding the pretreated carbon nanotube powder to a dimethylformamide solution, using The microporous filtration membrane is evacuated, and a pre-formed carbon nanotube film is formed on the microporous filtration membrane.

In one embodiment, the pre-formed carbon nanotube film has a thickness of 100 to 300 μm.

S140, obliquely inserting the microporous filter film formed with the pre-formed carbon nanotube film into deionized water, and peeling off the carbon nanotube film from the pre-formed carbon nanotube film;

In one embodiment, the carbon nanotube film has a thickness of 40-60 nm. Preferably, the carbon nanotube film has a thickness of 50 nm.

S150, after the carbon nanotube film is air-dried, the carbon nanotube film is placed on the PDMS film of the conical microarray structure, and heated at a temperature of 180-220 ° C for 20-40 minutes;

S160, coating a PDMS solution containing PDMS and a crosslinking agent on a silicon wafer, and heating at 70-90 ° C for 20-30 minutes, and then standing to cool to room temperature to obtain a semi-cured smooth PDMS film.

The uncured PDMS film is tacky and can be better bonded to the PDMS film for carbon nanotube film and conical microarray construction.

S170, attaching the semi-cured smooth PDMS film to the carbon nanotube film, and heating at a temperature of 70-90 ° C for 20-30 minutes to form a sandwich structure, that is, a flexible pressure sensor.

In one embodiment, the two sides of the sandwich structure intermediate layer of the flexible pressure sensor are further provided with electrodes.

The above steps are not used to limit the sequence of the preparation method of the flexible pressure sensor of the present application. In this embodiment, a PDMS film of a conical microarray structure is prepared, then a carbon nanotube film is prepared, and a smooth PDMS film is prepared. The three are laminated to obtain a flexible pressure sensor. In other embodiments, the order of preparation of the three may also be reversed, and finally the three are laminated to obtain a flexible pressure sensor.

Referring to FIG. 4, a flexible pressure sensor according to an embodiment comprises: a PDMS film of a conical microarray structure, a carbon nanotube film, and a smooth PDMS film which are sequentially stacked. The carbon nanotube film is adhered to the surface of the PDMS film; the smooth PDMS film is placed on the carbon nanotube layer. The flexible pressure sensor is obtained by the above preparation method. The specific method has been described in detail and will not be described again.

In one embodiment, the PDMS film has a thickness of from 150 to 250 [mu]m.

In one embodiment, the carbon nanotube film has a thickness of 40-60 nm.

In one embodiment, electrodes are respectively disposed on both sides of the carbon nanotube film of the intermediate layer of the flexible pressure sensor sandwich structure.

The above-mentioned embodiments are merely illustrative of several embodiments of the present invention, and the description thereof is more specific and detailed, but is not to be construed as limiting the scope of the invention. It should be noted that a number of variations and modifications may be made by those skilled in the art without departing from the spirit and scope of the invention. Therefore, the scope of the invention should be determined by the appended claims.

Claims

A method for preparing a flexible pressure sensor, wherein the preparation method comprises:

The PDMS solution containing PDMS and cross-linking agent is coated on a mold having an array of conical groove structures, heated at 70-90 ° C for 30-60 minutes, left to cool to room temperature, and the PDMS film is separated from the mold. Obtaining a PDMS film having a conical microarray structure;

Adding carbon nanotube powder to a mixed solution of hydrogen chloride and hydrogen peroxide, and preheating at a temperature of 55-65 ° C for 3.5-4.5 hours;

The pretreated carbon nanotube powder is added to the dimethylformamide solution, vacuum leaking is performed by using a microporous filtration membrane, and a pre-formed carbon nanotube film is formed on the microporous filtration membrane;

The microporous filtration membrane formed with the pre-formed carbon nanotube film is obliquely inserted into deionized water, and the carbon nanotube film is peeled off from the pre-formed carbon nanotube film;

After the carbon nanotube film is air-dried, the carbon nanotube film is placed on the PDMS film of the conical microarray structure, and heated at a temperature of 180-220 ° C for 20-40 minutes;

The PDMS solution containing PDMS and a crosslinking agent is coated on a silicon wafer and heated at 70-90 ° C for 20-30 minutes, and left to cool to room temperature to obtain a semi-cured smooth PDMS film;

The semi-cured smooth PDMS film was attached to the carbon nanotube film and the PDMS film of a conical microarray structure, and heated at a temperature of 70-90 ° C for 20-30 minutes to obtain a sandwich-type flexible pressure sensor.
The method of manufacturing a flexible pressure sensor according to claim 1, wherein the preparation method further comprises: respectively extracting electrodes from both sides of the intermediate layer of the sandwich structure of the flexible pressure sensor.
The method of producing a flexible pressure sensor according to claim 1, wherein the weight ratio of the PDMS to the crosslinking agent is from 8:1 to 10:1.
The method of manufacturing a flexible pressure sensor according to claim 1, wherein the conical groove has a depth of 30 to 60 μm, and the conical surface has a diameter of 30 to 60 μm.
The method of manufacturing a flexible pressure sensor according to claim 1, wherein the PDMS film has a thickness of 150 to 250 μm.
The method of producing a flexible pressure sensor according to claim 1, wherein the volume ratio of hydrogen chloride to hydrogen peroxide is from 2:1 to 3:1.
The method of manufacturing a flexible pressure sensor according to claim 1, wherein the pre-formed carbon nanotube film has a thickness of 100 to 300 μm, and the carbon nanotube film has a thickness of 40 to 60 nm.
A flexible pressure sensor obtained according to the method of claim 1, wherein the flexible pressure sensor comprises:

a PDMS film of a conical microarray structure;

a carbon nanotube film bonded to the surface of the PDMS film; and

A smooth PDMS film placed on the carbon nanotube layer.
The flexible pressure sensor according to claim 8, wherein the PDMS film has a thickness of 150 to 250 μm, and the carbon nanotube film has a thickness of 40 to 60 nm.
The flexible pressure sensor according to claim 8, wherein electrodes of the intermediate layer of the sandwich structure of the flexible pressure sensor are respectively provided with electrodes.