CN114262520B

CN114262520B - Preparation method of flexible stretchable silicone rubber-based strain sensor based on emulsion blending

Info

Publication number: CN114262520B
Application number: CN202210064038.XA
Authority: CN
Inventors: 观姗姗; 唐尧凯; 王心成; 成尚儒; 高强民; 李安琦; 袁莹欣
Original assignee: Qingdao University of Science and Technology
Current assignee: Qingdao University of Science and Technology
Priority date: 2022-01-20
Filing date: 2022-01-20
Publication date: 2022-12-02
Anticipated expiration: 2042-01-20
Also published as: CN114262520A

Abstract

A preparation method of a flexible stretchable silicone rubber-based strain sensor based on emulsion blending belongs to the technical field of flexible electronic materials. According to the preparation method provided by the invention, graphene oxide and hydroxyl silicone oil emulsion are mixed, a GO/PDMS film is manufactured by blending latex to form a film, then, a conductive rGO/PDMS film is obtained by reducing GO/PDMS with sodium ascorbate, and the rGO/PDMS film is prepared into a sensor. The method has the beneficial effect that the rGO/PDMS sensor with the isolation network is constructed by using an emulsion assembly technology for the first time.

Description

Preparation method of flexible stretchable silicone rubber-based strain sensor based on emulsion blending

Technical Field

The invention belongs to the technical field of flexible electronic materials, and particularly relates to a preparation method of a flexible stretchable silicone rubber-based strain sensor based on emulsion blending.

Background

Strain sensors are important subcomponents of stretchable electronics that can convert the deformation caused by an external mechanical stimulus into electrical signals. Flexible, wearable polymer strain sensors have become a hotspot in the sensor field compared to commercial brittle strain sensors.

The flexible strain sensor generally consists of a flexible polymer matrix and conductive filler, and the working principle of the flexible strain sensor is that under the action of stress, the sensor is deformed, and an internal conductive network is damaged to different degrees, so that the sensor transmits the change of a resistance signal.

On the one hand, polydimethylsiloxane (PDMS) has become the most commonly used polymer matrix in flexible sensors due to its low elastic modulus and large strain response range. On the other hand, graphene Oxide (GO) and reduced graphene oxide (rGO) and their derivatives have excellent electrical conductivity and mechanical properties. The two-dimensional layered structure of graphene increases the contact area of the filler network, which reduces contact resistance due to damage of the filler and accelerates the network during strain generation. Therefore, the graphene/PDMS composite material is expected to achieve higher sensitivity under high strain. However, chemically inert PDMS is difficult to complex with graphene by direct blending methods.

Two common methods of making PDMS are backfilling PDMS into a network of interconnected conductive fillers and coating the conductive fillers on the surface of the PDMS. However, these two methods have many problems, and some composite materials are made by coating conductive fillers on the surface of PDMS, and the sensor prepared by this method has poor integrity, weak interaction between the fillers and PDMS, lack of environmental stability and operational stability, and generally require complicated and expensive processing route. In addition, the composite material prepared by the method of backfilling PDMS to the conductive filler network has high filler content, the flexibility of PDMS is damaged, only small strain can be generated, and the high filler content causes that the composite material is not easy to damage the filler network under the action of stress, so the application of the composite material prepared by the method in a sensor is greatly limited.

Disclosure of Invention

The invention aims to provide a preparation method of a flexible stretchable silicone rubber-based strain sensor based on emulsion blending.

The invention provides a preparation method of a flexible stretchable silicon rubber-based strain sensor based on emulsion blending, which comprises the following steps:

(1) Dispersing GO in deionized water to obtain a GO suspension;

(2) Slowly dripping the GO suspension into a hydroxyl silicone oil emulsion, uniformly mixing to obtain a mixed solution A, and controlling the PH value to be 7-8 in the mixing process;

(3) Heating the mixed solution A in a magnetic stirring process in a water bath until the volume of the mixed solution A is 2/3 of the volume of the mixed solution A, stopping heating, and cooling to room temperature to obtain mixed solution B;

(4) Dissolving sodium ascorbate in deionized water to obtain a sodium ascorbate water solution, slowly dripping the sodium ascorbate water solution into the mixed solution B, and magnetically stirring to obtain a mixed solution C;

(5) Slowly dripping a curing agent into the mixed solution C, and performing magnetic stirring to obtain a mixed solution D;

(6) Transferring the mixed solution D into a clean culture dish, placing the mixed solution D at room temperature, and then placing the mixed solution D into an oven for drying to obtain a solidified and film-formed GO/PDMS composite material;

(7) Immersing the GO/PDMS composite material in deionized water, carrying out water bath reduction, and then placing the GO/PDMS composite material in a drying oven for drying to obtain an rGO/PDMS composite material;

(8) Preparing the rGO/PDMS composite material into an rGO/PDMS strip, respectively fixing copper foils on two sides of the rGO/PDMS strip by using conductive silver paste, and placing the two sides of the rGO/PDMS strip in an oven for drying so as to cure the silver paste;

(9) And (4) encapsulating two sides by using a polyimide adhesive tape to obtain the rGO/PDMS flexible strain sensor.

Preferably, the addition amount of deionized water is 15ml for each of 0.009g,0.018g,0.027g,0.036g,0.054g and 0.072g GO, the addition amount of the corresponding hydroxyl silicone oil emulsion is 6g, the addition amount of the corresponding sodium ascorbate is 0.045g,0.09g,0.135g, 0.8g, 0.27g and 0.36g, and the addition amount of the corresponding curing agent is 0.018g.

Preferably, in the step (3), the rotation speed of the magnetic stirring is 500rpm, the temperature of the water bath is 60 ℃, and the time of the water bath is 2 hours.

Preferably, in the step (4), the rotation speed of the magnetic stirring is 500rpm, and the time of the magnetic stirring is 10min.

Preferably, in the step (5), the rotation speed of the magnetic stirring is 500rpm, and the time of the magnetic stirring is 15min.

Preferably, in the step (6), the room temperature is set for 8 hours, the drying temperature is 60 ℃, and the drying time is 6 hours.

Preferably, in the step (7), the temperature of the water bath is 60 ℃, the temperature of the water bath is 12 hours, the temperature of drying is 60 ℃, and the time of drying is 8 hours.

Preferably, in the step (8), the size of the strip is 1cm × 5cm, the drying temperature is 60 ℃, and the drying time is 6h.

Secondly, the invention provides a flexible stretchable silicon rubber-based strain sensor, and the preparation raw materials of the sensor comprise GO, hydroxyl silicone oil emulsion, sodium ascorbate, a curing agent and deionized water;

the preparation steps for preparing the sensor per 0.072g GO are as follows:

(1) Dispersing 0.072g GO in 15ml deionized water to obtain GO suspension;

(2) Slowly dripping the GO suspension into 6g of hydroxyl silicone oil emulsion, uniformly mixing to obtain a mixed solution A, and controlling the PH value to be 7-8 in the mixing process;

(3) Heating the mixed solution A in a water bath at 60 ℃ in the magnetic stirring process to 2/3 volume of the mixed solution A, stopping heating, and cooling to room temperature to obtain mixed solution B;

(4) Dissolving 0.36g of sodium ascorbate in deionized water to obtain a sodium ascorbate water solution, slowly dripping the sodium ascorbate water solution into the mixed solution B, and stirring for 10min by magnetic stirring at 500rpm to obtain a mixed solution C;

(5) Slowly dripping 0.018g of curing agent into the mixed solution C, and performing magnetic stirring for 15min at 500rpm to obtain a mixed solution D;

(6) Transferring the mixed solution D to a clean culture dish, standing at room temperature for 8 hours, and then putting into a drying oven to dry at 60 ℃ for 6 hours to obtain a solidified and film-formed GO/PDMS composite material;

(7) Immersing the GO/PDMS composite material into 300ml of deionized water, reducing the GO/PDMS composite material in a water bath at 60 ℃ for 12h, and then drying the GO/PDMS composite material in an oven to obtain an rGO/PDMS composite material;

(8) Preparing the rGO/PDMS composite material into a rGO/PDMS strip, and respectively fixing copper foils on two sides of the rGO/PDMS strip by using conductive silver paste, and drying the two sides in an oven at 60 ℃ for 6 hours to solidify the silver paste;

The beneficial effects of the invention are:

the invention firstly uses the emulsion assembly technology to construct the rGO/PDMS sensor with the isolation network, and the method is simple, has lower cost and can easily amplify the rGO/PDMS sensor in proportion. The sensor prepared by the invention can still keep high sensitivity (GF = 44.01) under the high stretching rate of 300%%, has the characteristics of 165ms quick response, long-term circulation stability (30% strain 2500 times) and the like, can detect motion signals such as human joint bending and the like and physiological signals such as pulse and the like, and has outstanding advantages in human signal detection. Therefore, the preparation method provided by the invention can be applied in the field of wearable electronic equipment in a large scale.

Drawings

FIG. 1 schematic view of rGO/PDMS compliant strain sensor;

FIG. 2 is a digital photograph of the rGO/PDMS composite prepared;

the method comprises the following steps of (a) placing an rGO/PDMS film on a pistil, (b) preparing rGO/PDMS films with different shapes, and (c) amplifying an optical picture of the prepared rGO/PDMS film by a process (20 cm multiplied by 13 cm);

FIG. 3 SEM and TEM pictures of rGO/PDMS films

(a) 10um SEM picture (b) 2um SEM picture (c) 1um TEM picture (d) 500nm TEM picture;

FIG. 4 mechanical property measurements of rGO/PDMS films;

(a) Photographs of rGO/PDMS at 0%, 100%, 200% and 200g weight loading; (b) stress-strain curves for PDMS and rGO/PDMS films;

FIG. 5 detection results of strain sensing performance of rGO/PDMS film

(a) relative resistance change of rGO/PDMS strain sensor with respect to applied strain and GF in different linear regions; (b) Response time to changes in relative resistance under rapid loading and unloading; (c) Relative resistance change at 30% strain is repeatedly loaded and unloaded;

FIG. 6 the effect of the sensor detecting full finger movement and pulse;

(a) The sensor is assembled on the finger joint to detect the bending movement of the finger; and (b) the sensor is attached to the wrist to detect the pulse.

Detailed Description

In order to clearly explain the technical features of the present solution, the present solution is explained by the following detailed description.

Example 1

(1) Dispersing 0.072g GO in 15ml deionized water to obtain GO suspension;

(4) Dissolving 0.36g of sodium ascorbate in deionized water to obtain a sodium ascorbate water solution, slowly dropwise adding the sodium ascorbate water solution into the mixed solution B, and stirring for 10min by magnetic stirring at 500rpm to obtain a mixed solution C;

(5) Slowly dripping 0.018g of curing agent into the mixed solution C, and carrying out magnetic stirring for 15min at 500rpm to obtain mixed solution D;

(6) Transferring the mixed solution D into a clean culture dish, standing at room temperature for 8h, and then putting into a drying oven for drying at 60 ℃ for 6h to obtain a solidified and film-formed GO/PDMS composite material;

(7) Immersing the GO/PDMS composite material in 300ml of deionized water, reducing in a water bath at 60 ℃ for 12h, and then placing in an oven for drying to obtain an rGO/PDMS composite material;

(8) Preparing an rGO/PDMS composite material into an rGO/PDMS strip, respectively fixing copper foils on two sides of the rGO/PDMS strip by using conductive silver paste, and drying the copper foils in an oven at 60 ℃ for 6 hours to cure the silver paste;

(9) And (3) encapsulating two sides by using a polyimide adhesive tape to obtain the rGO/PDMS flexible strain sensor, wherein the prepared rGO/PDMS flexible strain sensor is shown in figure 1.

Example 2

(1) Dispersing 0.009g GO in 15ml deionized water to obtain GO suspension;

(2) Slowly dripping GO suspension into 6g of hydroxyl silicone oil emulsion, uniformly mixing to obtain a mixed solution A, and controlling the PH value to be 7-8 in the mixing process;

(4) Dissolving 0.045g of sodium ascorbate in deionized water to obtain a sodium ascorbate water solution, slowly dropwise adding the sodium ascorbate water solution into the mixed solution B, and stirring for 10min by magnetic stirring at 500rpm to obtain a mixed solution C;

(8) Preparing a rGO/PDMS composite material into a rGO/PDMS strip, and respectively fixing copper foils on two sides of the rGO/PDMS strip by using conductive silver paste and placing the two sides in an oven for drying at 60 ℃ for 6 hours to solidify the silver paste;

Example 3

(1) Dispersing 0.018g GO in 15ml deionized water to obtain GO suspension;

(4) Dissolving 0.09g of sodium ascorbate in deionized water to obtain a sodium ascorbate aqueous solution, slowly dropwise adding the sodium ascorbate aqueous solution into the mixed solution B, and magnetically stirring at 500rpm for 10min to obtain a mixed solution C;

Example 4

(1) Dispersing 0.027g of GO in 15ml of deionized water to obtain a GO suspension;

(4) Dissolving 0.135g of sodium ascorbate in deionized water to obtain a sodium ascorbate aqueous solution, slowly dropwise adding the sodium ascorbate aqueous solution into the mixed solution B, and magnetically stirring at 500rpm for 10min to obtain a mixed solution C;

Example 5

(1) Dispersing 0.036g of GO in 15ml of deionized water to obtain a GO suspension;

(4) Dissolving 0.18g of sodium ascorbate in deionized water to obtain a sodium ascorbate water solution, slowly dropwise adding the sodium ascorbate water solution into the mixed solution B, and stirring for 10min by magnetic stirring at 500rpm to obtain a mixed solution C;

(7) Immersing the GO/PDMS composite material in 300ml of deionized water, reducing in a water bath at 60 ℃ for 12h, and then drying in an oven to obtain a rGO/PDMS composite material;

Example 6

(1) Dispersing 0.054g of GO in 15ml of deionized water to obtain GO suspension;

(4) Dissolving 0.27g of sodium ascorbate in deionized water to obtain a sodium ascorbate water solution, slowly dropwise adding the sodium ascorbate water solution into the mixed solution B, and stirring for 10min by magnetic stirring at 500rpm to obtain a mixed solution C;

(9) And (3) encapsulating two sides by using a polyimide adhesive tape to obtain the rGO/PDMS flexible strain sensor.

Example 7

(1) Dispersing 0.72g of GO in 150ml of deionized water to obtain a GO suspension;

(2) Slowly dripping GO suspension into 60g of hydroxyl silicone oil emulsion, uniformly mixing to obtain a mixed solution A, and controlling the PH value to be 7-8 in the mixing process;

(4) Dissolving 3.6g of sodium ascorbate in deionized water to obtain a sodium ascorbate aqueous solution, slowly dropwise adding the sodium ascorbate aqueous solution into the mixed solution B, and magnetically stirring at 500rpm for 10min to obtain a mixed solution C;

(5) Slowly dripping 0.18g of curing agent into the mixed solution C, and performing magnetic stirring for 15min at 500rpm to obtain mixed solution D;

(7) Immersing the GO/PDMS composite material in 3000ml of deionized water, reducing in a water bath at 60 ℃ for 12h, and then placing in an oven for drying to obtain an rGO/PDMS composite material;

Example 8

(1) Detecting the basic performance of the rGO/PDMS membrane prepared by the invention;

(2) The results of the detection are shown in FIG. 2;

it can be seen from figure 2 that rGO/PDMS films are light enough to be easily placed on the pistil and can be easily folded or cut into different shapes, such as bowties, stars or hearts. Furthermore, the emulsion film forming process can be easily scaled up to obtain rGO/PDMS films of 20cm x 13cm or larger size. The above results show that the rGO/PDMS film prepared by the invention has the advantages of ultra-light weight, flexibility and processability, and is beneficial to constructing flexible electronic devices.

Example 9

(1) Detecting the internal structure of the rGO/PDMS membrane prepared by the invention;

(2) The results of the detection are shown in FIG. 3;

from FIGS. 3a-b, it can be seen that the uniform distribution of GO in the PDMS matrix; as can be seen in fig. 3c-d, the PDMS matrix presents an interconnected filler network.

Example 10

(1) Detecting the mechanical property of the rGO/PDMS membrane prepared by the invention;

(2) The results of the detection are shown in FIG. 4;

as can be seen in fig. 4a, rGO/PDMS films exhibit excellent flexibility, which can be stretched 100% or even 200%. In addition, the film can easily lift up a weight of 200 grams, demonstrating the high strength of the rGO/PDMS film.

Example 11

(1) Detecting the strain sensing performance of the rGO/PDMS sensor prepared by the invention;

(2) The sensor is arranged on a universal material testing machine and is connected to the digital source meter through two wires;

(3) The results obtained are shown in FIG. 5;

FIG. 5a shows the corresponding Δ R/R ₀ (Δ R is the change in resistance with strain, R ₀ Resistance before strain) and strain (epsilon, 0-300%), it can be seen that the delta R/R of the rGO/PDMS sensor ₀ The increase can be kept constant, with epsilon up to 300%. As shown in FIG. 5a, according to Δ R/R ₀ The difference in the rate of change divides the sensitivity (GF) into four linear regions, each having a high coefficient of determination. With increasing strain, the sensor exhibits greater GF. GF reaches a high value of 44.01 at a strain of 230-300%, achieving a large stretchability and a high sensitivity.

FIG. 5b shows the sensing time of the rGO/PDMS sensor, and it can be seen that the rGO/PDMS sensor has a fast response time of 165ms and a recovery time of 248ms when 100% strain is loaded and released, showing excellent response capability.

FIG. 5c shows the durability and reproducibility of the rGO/PDMS sensor, and it can be seen that after 2500 load-unload cycles, almost no Δ R/R is observed ₀ The signal waveforms of 1620s-1670s and 4000s-4050s are consistent in the circulating process, and the sensor has high repeatability.

Example 12

(1) Detecting the application effect of the prepared rGO/PDMS sensor in detecting the bending of fingers and monitoring the pulse;

(2) The obtained results are shown in FIG. 6.

As can be seen from fig. 6a, the resistance signal of the sensor exhibits a unique step-like characteristic when the finger is continuously bent from 0 ° to 90 °. Therefore, the sensor is expected to be used for postoperative monitoring and joint rehabilitation.

The inset in fig. 6b is an enlarged view of a single pulse from which the three peaks of the impinging (P1), tidal (P2) and diastolic (P3) waves can be seen, it is clear that the rGO/PDMS sensor can distinguish between different pulse microvibrations, which suggests its potential application as a heart rate sensor for monitoring physiological signals.

The technical features of the present invention which are not described in the above embodiments may be implemented by or using the prior art, and are not described herein again, of course, the above description is not intended to limit the present invention, and the present invention is not limited to the above examples, and variations, modifications, additions or substitutions which may be made by those skilled in the art within the spirit and scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A preparation method of a flexible stretchable silicone rubber-based strain sensor based on emulsion blending is characterized by comprising the following steps:

(1) Dispersing GO in deionized water to obtain a GO suspension;

(2) Slowly dripping the GO suspension into the hydroxyl silicone oil emulsion, uniformly mixing to obtain a mixed solution A, and controlling the PH value to be 7-8 in the mixing process;

(7) Immersing the GO/PDMS composite material in deionized water, carrying out water bath reduction, and then placing the GO/PDMS composite material in an oven for drying to obtain an rGO/PDMS composite material;

2. The preparation method of claim 1, wherein the deionized water is added in an amount of 15ml for each of 0.009g,0.018g,0.027g,0.036g,0.054g and 0.072g GO, the hydroxyl silicone oil emulsion is added in an amount of 6g, the sodium ascorbate is added in an amount of 0.045g,0.09g,0.135g,0.18g,0.27g and 0.36g, and the curing agent is added in an amount of 0.018g.

3. The method according to claim 1, wherein in the step (3), the rotation speed of the magnetic stirring is 500rpm, the temperature of the water bath is 60 ℃, and the time of the water bath is 2h.

4. The method according to claim 1, wherein in the step (4), the rotation speed of the magnetic stirring is 500rpm, and the time of the magnetic stirring is 10min.

5. The method according to claim 1, wherein in the step (5), the rotation speed of the magnetic stirring is 500rpm, and the time of the magnetic stirring is 15min.

6. The preparation method according to claim 1, wherein in the step (6), the room temperature is kept for 8 hours, the drying temperature is 60 ℃, and the drying time is 6 hours.

7. The preparation method according to claim 1, wherein in the step (7), the temperature of the water bath is 60 ℃, the temperature of the water bath is 12h, the temperature of the drying is 60 ℃, and the time of the drying is 8h.

8. The method according to claim 1, wherein in the step (8), the size of the strip is 1cm x 5cm, the temperature of the drying is 60 ℃, and the time of the drying is 6h.

9. The flexible stretchable silicon rubber-based strain sensor is characterized in that the preparation raw materials of the sensor comprise GO, hydroxyl silicone oil emulsion, sodium ascorbate, a curing agent and deionized water;

the preparation steps for preparing the sensor per 0.072g GO are as follows:

(1) Dispersing 0.072g GO in 15ml deionized water to obtain GO suspension;

(6) Transferring the mixed solution D into a clean culture dish, standing at room temperature for 8h, and then putting into a drying oven to dry for 6h at 60 ℃ to obtain a solidified and film-formed GO/PDMS composite material;

(7) Immersing the GO/PDMS composite material into 300ml of deionized water, reducing the GO/PDMS composite material in a water bath at 60 ℃ for 12 hours, and then drying the GO/PDMS composite material in an oven to obtain an rGO/PDMS composite material;

(8) Preparing the rGO/PDMS composite material into an rGO/PDMS strip, respectively fixing copper foils on two sides of the rGO/PDMS strip by using conductive silver paste, and drying the copper foils in an oven at 60 ℃ for 6 hours to cure the silver paste;