CN110606981A - Pressure sensor, preparation method and application thereof, and wearable intelligent fabric comprising pressure sensor - Google Patents

Abstract

The invention provides a pressure sensor, a preparation method and application thereof, and a wearable intelligent fabric containing the pressure sensor. The pressure sensor is graphene modified polyurethane foam; wherein the graphene is 0.8-2.5% by mass based on 100% by mass of the total graphene-modified polyurethane foam. The wearable intelligent fabric prepared by the sensor provided by the invention is a wearable platform completely based on fabric, and has wide application value.

Description

Pressure sensor, preparation method and application thereof, and wearable intelligent fabric comprising pressure sensor

Technical Field

The invention belongs to the technical field of sensors, and relates to a pressure sensor, a preparation method and application thereof, and a wearable intelligent fabric containing the pressure sensor.

Background

The development of smart sensors has attracted considerable interest over the last 30 years, as they have great potential for use in almost all industries, health, sports, the environment, etc. The traditional strain sensor is mainly based on metal and semiconductor materials, and has certain sensitivity, but the defects that the materials are usually metal-based, are generally hard and uncomfortable to wear for a long time, and meanwhile, the materials do not have transparency and viscoelasticity, and have low stretchability and sensitivity, and even need to be embedded into the skin to accurately measure the health and physiological signals of a human body, so that the application range of the strain sensor is limited. For sensors, the material that responds to physical stimuli (such as stretching and pressing) plays a crucial role, as it is the key part that responds to external factors and converts them into signals.

Compared with the traditional strain sensor, the flexible multifunctional strain sensor overcomes the defect of hard material, has the characteristics of ultra-thinness, ultra-lightness, flexibility, stretchability, sensitivity, wearability and the like, and simultaneously shows better biocompatibility and continuous detection advantages. In flexible multifunctional strain sensors, the active material and the flexible substrate are the key to determining the performance of the sensor. Commonly used active materials for flexible multifunctional strain sensors reported to date include: the flexible multifunctional strain sensor based on the organic material has the advantages of being the most rapid in development, simple in preparation process and good in flexibility, but the application range and the response time of the flexible multifunctional strain sensor are limited to a certain extent.

Graphene is considered one of the most promising materials due to its advantageous properties, including exceptional thermal (conductive and stable), mechanical (flexible and strong), electrical (highly conductive) properties and good strain coefficient. In addition, graphene is nontoxic to human bodies and the environment, and the graphene-based sensor is more comfortable to wear and is an ideal choice for a body contact type sensor.

CN105067159A discloses a capacitive pressure sensor and a method for manufacturing the same, wherein the capacitive pressure sensor is composed of an insulating layer and two substrates containing electrodes, the insulating layer is located between the two electrodes, the insulating layer is a porous elastic film, which reduces the cost of the capacitive pressure sensor, but does not really realize a wearable function on a base fabric. CN105387927A discloses a novel flexible vibration sensor, including three-dimensional graphite alkene and elasticity polymer base member, three-dimensional graphite alkene is wrapped inside elasticity polymer base member, and the both ends of three-dimensional graphite alkene are provided with the wire and wear out elasticity polymer base member, and the wire passes through the silver colloid and is connected with three-dimensional graphite alkene, and this patent spectrum is wide, but does not realize wearable fabric's assumption yet to in the use, because graphite alkene and elasticity polymer adhesion nature are not high, sensor life is shorter. CN106767374A discloses a preparation method of a flexible multifunctional strain sensor based on a three-dimensional graphene/carbon nanotube network, the method grows a three-dimensional network of three-dimensional graphene and one-dimensional carbon nanotubes by a two-step chemical vapor deposition method, and the three-dimensional network is solidified and combined with an elastic polymer serving as a flexible substrate to obtain the flexible wearable multifunctional electronic strain sensor based on the three-dimensional network of graphene and carbon nanotubes, but the sensitivity of the flexible wearable multifunctional electronic strain sensor is not high enough, and the flexible wearable multifunctional electronic strain sensor corresponds to sensing through stretching and is inconvenient to apply.

Therefore, there is a need to provide a wearable smart fabric that can be truly implemented to meet the current application requirements for sensors.

Disclosure of Invention

The invention provides a pressure sensor, a preparation method and application thereof, and a wearable intelligent fabric containing the pressure sensor. The pressure sensor provided by the invention is the graphene modified polyurethane foam, and on the polyurethane foam, the graphene is high in load amount and has better adhesion to a polyurethane substrate, so that the sensitivity and the service life of the sensor can be improved. Meanwhile, the wearable intelligent fabric prepared by the sensor is a wearable platform completely based on fabric, and has wide application value.

In order to achieve the purpose, the invention adopts the following technical scheme:

in a first aspect, the invention provides a pressure sensor, wherein the pressure sensor is graphene modified polyurethane foam.

Wherein the graphene is 0.8-2.5% by mass, for example, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0%, 2.2%, 2.4% and the like, based on 100% by mass of the total graphene-modified polyurethane foam.

In the graphene modified polyurethane foam provided by the invention, the load of graphene is high, and the graphene has a good adhesion effect on the polyurethane foam, so that the pressure sensor provided by the invention has sensitive reaction and long service life, and meanwhile, the graphene is nontoxic to the environment and human body, and is beneficial to being applied to wearable intelligent fabrics.

Preferably, the polyurethane foam has a porosity of 94-96%, such as 95%, and the like.

In a second aspect, the present invention provides a method for manufacturing a pressure sensor according to the first aspect, the method comprising the steps of:

treating the polyurethane foam by using a graphene oxide solution to obtain a polyurethane foam loaded with graphene oxide; and then reducing the graphene oxide to obtain the pressure sensor.

As a preferred technical scheme, the preparation method comprises the following steps:

(1) soaking polyurethane foam in graphene oxide ethanol solution, air drying and drying at 70-90 deg.C (such as 75 deg.C, 80 deg.C, 85 deg.C, etc.);

(2) and reducing the graphene oxide on the dried polyurethane foam by using a reducing agent, and then washing and drying to obtain the pressure sensor.

The polyurethane foam is soaked in the ethanol solution of the graphene oxide, the ethanol permeates into the polyurethane foam, the polyurethane foam has certain swelling, the swelling increases the specific surface area of the polyurethane foam, and further the quantity of the graphene oxide entering the polyurethane foam and the depth of the graphene oxide entering the polyurethane foam are increased. When the solvent is removed by heating at 70-90 ℃, the polyurethane foam shrinks, so that the strong adhesion of graphene oxide on the polyurethane foam is increased, and the graphene oxide layers have better stacking property. The preparation method provided by the invention improves the strength of polyurethane foam and the firmness of the finally obtained pressure sensor, and the finally obtained pressure sensor has higher stability and conductivity.

The graphene modified polyurethane foam with the firm graphene coating is prepared by the preparation method provided by the invention, loose graphene particles cannot be generated in the preparation method provided by the invention, and therefore, the graphene modified polyurethane foam provided by the invention is stable to friction or multiple times of water washing.

Preferably, the reducing agent comprises hydrazine hydrate.

Preferably, the preparation method of the graphene oxide comprises the following steps: and oxidizing the graphite flake in concentrated sulfuric acid by using an oxidant, and then washing and dialyzing to obtain the graphene oxide.

Preferably, the mass ratio of the graphite flake to the oxidizing agent is 1 (2-6), such as 1:3, 1:4, 1:5, and the like.

Preferably, the oxidizing agent comprises potassium dichromate and/or potassium permanganate.

Preferably, the concentrated sulfuric acid is used in an amount of 20-50mL (e.g., 30mL, 40mL, etc.) of concentrated sulfuric acid per 1g of graphite flake.

Preferably, the oxidizing agent is added to the concentrated sulfuric acid solution in portions.

Preferably, the solution temperature is maintained at 0-5 ℃ during the addition of the oxidizing agent.

Preferably, after the addition of the oxidizing agent is completed, the temperature is raised to room temperature, and then ultrasonic treatment is performed for 0.5-1h, such as 0.6h, 0.7h, 0.8h, 0.9h and the like.

Preferably, after the ultrasonic treatment is completed, deionized water is added into the reaction system, and then the reaction is carried out for 1-2h, such as 1.2h, 1.4h, 1.6h, 1.8h and the like at 98 ℃.

Preferably, the volume ratio of the deionized water to the concentrated sulfuric acid is (1.5-4):1, such as 2:1, 2.5:1, 3:1, 3.5:1, and the like.

Preferably, the method further comprises removing unreacted oxidizing agent with hydrogen peroxide after the reaction is completed.

Preferably, the washing comprises washing with hydrochloric acid, deionized water in sequence, and finally dialyzing in deionized water by using a dialysis bag until the pH is neutral.

As a preferred technical scheme for preparing graphene oxide, the preparation method is as follows:

adding graphene sheets into concentrated sulfuric acid, wherein 50mL of concentrated sulfuric acid is used for every 1g of graphite sheets; keeping the temperature of the reaction solution at 0-5 ℃, and adding potassium dichromate in batches, wherein the dosage of the potassium dichromate is 3 times that of the graphene; slowly heating to room temperature after the potassium dichromate is added, then carrying out ultrasonic treatment for 1h, and adding deionized water after the ultrasonic treatment, wherein the volume ratio of the deionized water to concentrated sulfuric acid is 5: 3; slowly heating to 98 ℃ and reacting for 1h, and then cooling to room temperature to complete the reaction. After the reaction is finished, adding hydrogen peroxide to remove residual potassium dichromate, filtering, washing with 0.5M hydrochloric acid for at least three times, washing with deionized water, and transferring the product to a dialysis bag immersed in the deionized water until the pH value of the water is neutral; and obtaining the graphene oxide.

According to the invention, the graphene oxide is prepared by improving the Hummer method, so that the structural defects of the graphene oxide can be reduced.

Preferably, the concentration of graphene oxide in the ethanol solution of graphene oxide is 0.5-2.5mg/mL, such as 0.6mg/mL, 0.8mg/mL, 1mg/mL, 1.4mg/mL, 1.6mg/mL, 1.8mg/mL, 2.0mg/mL, 2.2mg/mL, 2.4mg/mL, and the like.

Preferably, the soaking time is 20-30min, such as 22min, 24min, 26min, 28min, 29min and the like.

Preferably, the air-drying time is at least 4h, such as 4h, 4.5h, 4.8h, 5h, 6h, 8h, etc.

Preferably, the drying temperature in step (1) is 70-100 deg.C, such as 75 deg.C, 80 deg.C, 85 deg.C, 90 deg.C, etc., and the drying time is 60-120min, such as 70min, 80min, 90min, 100min, 110min, etc.

Preferably, the hydrazine hydrate is present in a concentration of 5-10%, e.g., 6%, 7%, 5.4%, 8%, 9%, etc., in the hydrazine hydrate solution.

Preferably, the reduction is carried out at a temperature of 80-95 deg.C, e.g., 84 deg.C, 88 deg.C, 90 deg.C, 94 deg.C, etc., and for a time of 3-4h, e.g., 3.2h, 3.4h, 3.6h, 3.8h, etc.

Preferably, the drying in step (2) is carried out at a temperature of 70-100 deg.C, such as 75 deg.C, 80 deg.C, 85 deg.C, 90 deg.C, etc., for a period of 4 hours or more, such as 4 hours, 5 hours, 10 hours, 12 hours, etc.

The preparation method provided by the invention can realize the control of the graphene load capacity, so that the graphene on the polyurethane foam can realize a large amount of load, and further the sensitivity of the pressure sensor (graphene modified polyurethane foam) can be increased; meanwhile, the preparation method provided by the invention can realize good adhesion of graphene on polyurethane foam, so that the service life of the sensor can be prolonged, and the sensor failure caused by separation of graphene from polyurethane foam in the use process is avoided.

In a third aspect, the invention provides the use of a pressure sensor according to the first aspect in a wearable smart fabric.

Preferably, the fabric comprises a glove, wristband, waistband, apron, pants or knee strap.

The sensor provided by the invention can be used for preparing wearable fabrics such as intelligent wristlets, intelligent gloves and the like, and is a real intelligent platform based on fabric base materials.

In a fourth aspect, the invention provides a wearable smart fabric comprising the pressure sensor of the first aspect.

Preferably, the device further comprises a conversion circuit, a microcontroller, a power supply and a substrate.

When the intelligent wrist strap provided by the invention is applied, if the intelligent wrist strap is required, the pressure sensor is pressed or pressed, the pressure sensor receives a signal and then converts the signal into an electric signal, and the electric signal is encoded by a designed program through the received electric signal, and finally, a specific command or function is executed.

In a fifth aspect, the invention provides a use of a pressure sensor according to the first aspect in a wearable keyboard, a wearable console, a wearable detector or a communication device.

The pressure sensor provided by the invention can also be applied to the fields of wearable keyboards, control consoles and the like, and the working mode of the equipment is similar to that of the existing keyboard, so that the equipment can be used as a human-computer interface control.

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

the pressure sensor provided by the invention is the graphene modified polyurethane foam, in the polyurethane foam, the graphene is higher in load capacity, and the graphene has better adhesion to polyurethane, so that the sensitivity of the sensor can be improved, and the service life of the sensor can be prolonged. Meanwhile, the wearable intelligent fabric prepared by the sensor is a wearable platform completely based on fabric, and has wide application value.

Drawings

FIG. 1 is a schematic structural view of a test assembly constructed in accordance with the present invention;

1-impedance; 2-a pressure sensor; 3-voltage; 4-data output terminal.

Fig. 2 is a graph showing the results of a spot pressure test performed on a test assembly.

Fig. 3 is a graph showing the results of a press test performed by the test assembly.

Fig. 4 is a schematic structural diagram of a wearable smart wristband according to application example 1.

401-an array of pressure sensors; 402-data connection layer; 403-data reading area; 404-a loudspeaker; 405-a power source; 406-an LED; 407-electrical connection layer.

Fig. 5 is a schematic diagram of a wearable smart band dial provided in application example 1.

Fig. 6 is a schematic diagram of a wearable smart apron provided in application example 2.

Fig. 7 is a schematic diagram of wearable smart pants provided in application example 3.

Fig. 8 is a schematic diagram of a wearable keyboard provided in application example 4.

Among them, 801 — microcontroller.

Detailed Description

The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.

Preparation example 1

A preparation method of graphene modified polyurethane foam comprises the following steps:

(1) preparation of graphene oxide

Adding 5g of graphite flake into 150mL of concentrated sulfuric acid, keeping the temperature of the reaction solution at 0-5 ℃, adding 15g of potassium dichromate in batches, slowly warming the obtained mixture to room temperature, then carrying out ultrasonic treatment for 1h, adding 250mL of deionized water into a flask, heating the flask in a water bath, slowly raising the temperature to 98 ℃, keeping the temperature for 1h, and cooling to room temperature. 60mL of 30% hydrogen peroxide was slowly added to remove residual oxidizing agent, the resulting product was filtered with a pump, rinsed at least 3 times with 0.5M hydrochloric acid to remove residue, then excess deionized water was added, and finally the product was transferred to a dialysis bag in a 2000mL beaker with deionized water to remove ions, with water being replaced every two hours the first day and twice a day for six days, until the pH was neutral.

(2) Preparation of graphene-modified polyurethane foam

One 2X 1cm³The PU foam (milky white) is immersed in 1.16mg mL of GO ethanol solution for 20min, then the foam is removed, excessive liquid is extruded out, and air drying is carried out for at least 4 hours; drying the air-dried GO-coated foam in an oven at 90 ℃ for at least 60 min; the dried GO coated foam (yellow brown) was cooled to room temperature and then transferred to a beaker with hydrazine hydrate solution (5-6%) and heated at 80 ℃ for 3h, during the reduction the color of the foam changed from dark yellow to black; after reduction, the sample was washed with copious amounts of water, then pressed and ground in water to remove any loosely attached particles, and the sample was dried in an oven at 90 ℃ for at least 4 h.

Performance testing

The performance test of the pressure sensor provided by the preparation example is carried out by the following method:

as shown in fig. 1, a test assembly was constructed, which includes an impedance 1, a pressure sensor 2 provided in preparation example 1, and a voltage 3 connected at one end, a ground at one end, and a data output terminal 4, and was tested: a: point pressing; b: and (6) pressing.

The test results are shown in fig. 2 and 3, where the dotted line in fig. 2 shows the change in resistance with the pressure of the point pressure, and the dotted line in fig. 3 shows the change in resistance at the start and end of the pressure. As can be seen from the figure, the sensor can respond to the pressure, the pressing time is prolonged, and the response time is prolonged; the sensor provided by the invention can respond to tiny changes in the pressing process, and the response is sensitive.

Application example 1: upper body communication wrist strap for medical care (OB-nursing)

This application describes the use of an upper body wristband as a remote patient assistance system for a bedridden patient.

Fig. 4 and 5 are schematic diagrams of the wearable smart wristband provided in the present application example, and the label on the button shown in fig. 5 is an actual function indicator.

The present embodiment includes a pressure sensor array 401, a speaker 404, and an LED 406 as soft keys, which are connected through a data reading area 403 formed on a data connection layer 402 covering a power connection layer 407, respectively. The pressure sensors (also referred to as "soft keys") prepared in preparation example 1 were designed in different geometric shapes and sizes for easy user identification and easy operation. The wearable wristband is connected to a battery powered microcontroller unit with bluetooth through a connection track.

In fig. 5, soft keys with function indicators Medical (Medical support), Toilet (assist in using Toilet), Hygiene (assist in personal Hygiene), Drink (request for drinking water) are pressure sensor arrays, and Speaker is attached.

During operation, pressure may be applied using a finger or fingers. Activating a sensor or combination of sensors can activate a unique function or command. The selectively activated soft keys generate an electrical signal to the microcontroller that sends corresponding encoded information to a remote receiving system, such as a computer or smart device. A feedback loop from the receiving end ensures that the user notices the message by emitting a sound and flashing the LED.

In this embodiment, a wearable smart wristband may be used as a remote patient assistance system, the function of which is described below:

specified request	Soft keys	Mode of operation
			Medical support	Rectangle	Point pressing for 2 seconds
Toilet with auxiliary use	Triangle shape	Point pressing for 2 seconds
			Assisting personal hygiene	Circular shape	Point pressing for 2 seconds
Request for drinking water	Square shape	Point pressing for 2 seconds
			Emergency system	Any two or all 4 soft keys	Pressing for 4 seconds

A bedridden patient wearing the smart wristband may request his or her own needs by pressing or pressing a soft key to send a request message to a remote system (e.g., a computer or smart device) in the nurse station. A flashing LED indicator light and repeated short beeps on the speaker provide a confirmation of the transmission of the request to send. The acknowledgement of receipt of the request message is notified by repeating a long beep and a long flashing LED on the speaker.

Application example 2

This application provides a wearable smart apron where the wearable platform takes the form of an apron, as shown in fig. 6, and the soft keys are located in the middle portion of the apron, and may also be designed to make it easier for the user to reach with either of their hands.

Application example 3

The present application example provides a wearable smart pants, as shown in fig. 7, with soft keys located in the areas shown in the figure.

Application example 4: on-body communication keyboard for man-machine interaction (OB-association)

The present application example provides an application that can be used as a wearable keyboard that provides all the normal functions of a normal computer keyboard.

As shown in fig. 8, 12 soft keys similar to those on the mobile phone screen keypad are included. There are 8 alphanumeric keys and 4 special character keys. The operation is also similar to a common on-screen keyboard, short single click activates the first letter, short double click activates the second letter, and so on; "→" indicates the direction in which data is connected to the "microcontroller 801".

The applicant states that the present invention is illustrated by the above embodiments of the pressure sensor, the preparation method and the application thereof, and the wearable smart fabric comprising the same, but the present invention is not limited to the above process steps, i.e. it does not mean that the present invention must rely on the above process steps to be implemented. It will be apparent to those skilled in the art that any modification of the present invention, equivalent substitutions of selected materials and additions of auxiliary components, selection of specific modes and the like, which are within the scope and disclosure of the present invention, are contemplated by the present invention.

Claims (10)

1. The pressure sensor is characterized in that the pressure sensor is made of graphene modified polyurethane foam;

wherein the graphene is 0.8-2.5% by mass based on 100% by mass of the total graphene-modified polyurethane foam.

2. The pressure sensor of claim 1, wherein the polyurethane foam has a porosity of 94-96%.

3. A method for manufacturing a pressure sensor according to claim 1 or 2, characterized in that the method comprises the steps of:

treating polyurethane foam in a graphene oxide solution to obtain polyurethane foam loaded with graphene oxide; and then reducing the graphene oxide to obtain the pressure sensor.

4. The method of claim 3, comprising the steps of:

(1) soaking polyurethane foam in an ethanol solution of graphene oxide, air-drying and drying at 70-90 ℃;

(2) reducing graphene oxide on the dried polyurethane foam by using a reducing agent, and then washing and drying to obtain the pressure sensor;

preferably, the reducing agent comprises hydrazine hydrate.

5. The preparation method according to claim 3 or 4, wherein the preparation method of the graphene oxide is as follows: oxidizing a graphite flake in concentrated sulfuric acid by using an oxidant, and then washing and dialyzing to obtain graphene oxide;

preferably, the mass ratio of the graphite sheet to the oxidant is 1 (2-6);

preferably, the oxidizing agent comprises potassium dichromate and/or potassium permanganate;

preferably, the dosage of the concentrated sulfuric acid is 20-50mL of concentrated sulfuric acid per 1g of graphite flake;

preferably, the oxidizing agent is added to the concentrated sulfuric acid solution in portions;

preferably, the solution temperature is maintained at 0-5 ℃ during the addition of the oxidizing agent;

preferably, after the oxidant is added, the temperature is raised to the room temperature, and then ultrasonic treatment is carried out for 0.5 to 1 hour;

preferably, after the ultrasonic treatment is finished, adding deionized water into the reaction system, and then reacting for 1-2h at 98 ℃;

preferably, the volume ratio of the deionized water to the concentrated sulfuric acid is (1.5-4) to 1;

preferably, the method further comprises removing unreacted oxidizing agent by using hydrogen peroxide after the reaction is finished;

preferably, the washing comprises washing with hydrochloric acid, deionized water in sequence, and finally dialyzing in deionized water by using a dialysis bag until the pH is neutral.

6. The production method according to claim 4 or 5, wherein the concentration of the graphene oxide in the ethanol solution of graphene oxide is 0.5-2.5 mg/mL;

preferably, the soaking time is 20-30 min;

preferably, the air-drying time is at least 4 h;

preferably, the drying temperature in the step (1) is 70-100 ℃, and the time is 60-120 min.

7. A production method according to any one of claims 4 to 6, characterized in that the concentration of hydrazine hydrate in the hydrazine hydrate solution is 5 to 10%;

preferably, the reduction temperature is 80-95 ℃, and the reduction time is 3-4 h;

preferably, the drying temperature in the step (2) is 70-100 ℃, and the time is more than 4 h.

8. Use of a pressure sensor according to claim 1 or 2 in the preparation of a wearable smart fabric;

preferably, the fabric comprises a glove, wristband, waistband, apron, pants or knee strap.

9. A wearable smart fabric comprising the pressure sensor of claim 1 or 2;

preferably, the device further comprises a conversion circuit, a microcontroller, a power supply and a substrate.

10. Use of a pressure sensor according to claim 1 or 2 in a wearable keyboard, a wearable console, a wearable detector or a wearable communication device.