阅读说明：本技术 一种高灵敏度柔性应变传感器的制作方法 (Manufacturing method of high-sensitivity flexible strain sensor ) 是由 马一飞 王梅 黎子健 陈旭远 于 2021-09-06 设计创作，主要内容包括：本发明属于柔性应变传感器制作领域,柔性应变传感器需具备良好的延展性、高的灵敏度、宽检测范围,现有的高灵敏的柔性应变传感器存在检测范围低,制作方法复杂等问题；而具有较大的检测范围的应变传感器存在灵敏度低,检测下限高等问题,本发明提供一种高灵敏度柔性应变传感器的制作方法,通过等离子增强化学气相沉积系统,利用三维化二维材料力学性能和网状结构,使网状基底上的三维化二维材料为基础制作的传感材料在受到应力而导致应变时产生应变集中效果,产生敏感的拉力响应,实现对传感材料的微小应变的检测,提升了应变传感材料的灵敏度和力学性能,实现更大范围的应变响应。(The invention belongs to the field of flexible strain sensor manufacturing, wherein a flexible strain sensor needs to have good ductility, high sensitivity and wide detection range, and the existing high-sensitivity flexible strain sensor has the problems of low detection range, complex manufacturing method and the like; the invention provides a manufacturing method of a high-sensitivity flexible strain sensor, which is used for solving the problems of low sensitivity, high lower limit detection and the like of a strain sensor with a larger detection range.)

1. A manufacturing method of a high-sensitivity flexible strain sensor is characterized by comprising the following steps: through a plasma enhanced chemical vapor deposition system, a vertically oriented three-dimensional two-dimensional material grows on a mesh substrate, the mechanical property and the mesh structure of the three-dimensional two-dimensional material are utilized, a strain concentration effect is generated when a sensing material manufactured on the basis of the three-dimensional two-dimensional material on the mesh substrate is stressed to cause strain, a resistance value is changed due to the fact that the structure is changed remarkably locally, under the strain concentration effect, a resistance change signal of the sensing material is converted into a voltage signal through a Wheatstone bridge circuit, a voltage difference value before and after stretching is calculated, the actual strain of the sensing material is fed back through the voltage difference value, the detection of micro strain of the sensing material is achieved, and the flexible strain sensor manufactured by a high polymer elastic material specifically comprises the following steps:

step 1, a mesh screen is taken as a growth substrate, and the mesh screen is placed in a heating area of a plasma enhanced chemical vapor deposition system after being cleaned;

step 2, placing the substrate material in a heating area of a quartz tube cavity of a plasma enhanced chemical vapor deposition system, adjusting the quartz tube cavity to be in a vacuum state, starting a heating mode of the plasma enhanced chemical vapor deposition system, heating the substrate material in the quartz tube cavity to a preset temperature, introducing precursor gas after the temperature is stable, then starting a radio frequency plasma source, starting deposition, and keeping the temperature and the plasma power stable in the whole deposition process;

step 3, connecting the two ends of the mesh screen obtained in the step 2 with lead-out electrodes, coating a flexible polymer elastic material on the surface of the mesh screen, and connecting two ends of the electrodes with a strain signal processor;

step 4, cutting the mesh screen coated with the flexible polymer elastic material in the step 3, and removing the mesh screen substrate by etching according to the use requirement and the substrate material, wherein if the substrate is a metal mesh screen, the metal mesh screen needs to be removed by etching to ensure the flexibility of the sensing material; if the substrate is a non-metallic stretchable mesh, step 4 is omitted.

2. The method of claim 1, wherein the strain sensor comprises: the strain signal processor comprises a power module for providing stable voltage, a Wheatstone bridge circuit for detecting resistance change of the sensing material, a signal processing module for amplifying and filtering voltage signals and a signal acquisition module for acquiring signals, reading and displaying, wherein the power module is sequentially connected with the Wheatstone bridge circuit, the signal processing module and the signal acquisition module to form a loop.

3. The method of claim 2, wherein the strain sensor comprises: the power supply module comprises a button battery box voltage stabilizing circuit.

4. The method of claim 2, wherein the strain sensor comprises: the flexible strain sensor in the wheatstone bridge circuit is connected between the resistor R1 and ground.

5. The method of manufacturing a high sensitivity flexible strain sensor according to claim 1 or 2, wherein: the high-molecular elastic material is one or more of polydimethylsiloxane, Ecoflex (copolyester) series silica gel, parylene, polyetherimide, butyl rubber, thermoplastic polyurethane rubber and polyurethane.

6. The method of claim 1, wherein the strain sensor comprises: the mesh number of the net in the step 1 is 10-300 meshes.

7. The method of claim 1, wherein the strain sensor comprises: the deposited three-dimensional two-dimensional material in the step 2 is graphene, a carbon nano tube, tungsten disulfide and molybdenum disulfide; the precursor gas is one or more of hydrogen, methane, acetylene and oxygen; the precursor is one or more of molybdenum oxide, sulfur and tungsten oxide.

Technical Field

The invention relates to the technical field of flexible strain sensors, in particular to a manufacturing method of a high-sensitivity flexible strain sensor.

Background

The flexible strain sensor has good application prospects in various aspects such as human motion detection, personalized health detection, electronic skin and the like, and is widely concerned. In practical use, the flexible strain sensor needs to have good ductility, high sensitivity, and a wide detection range. However, the existing flexible strain sensor has the problems of high sensitivity, low detection range, complex manufacturing method and the like; and when the strain sensor has a large detection range, the problems of low sensitivity, high detection lower limit and the like exist. Therefore, it is necessary to produce a flexible strain sensor, which has high sensitivity, a low detection lower limit and an appropriate detection range, and which is also a portable signal acquisition device to realize portable display of signals.

Disclosure of Invention

Aiming at the problems, the invention provides a method for manufacturing a high-sensitivity strain sensor based on a vertically-oriented three-dimensional material, and solves the problems of insufficient sensitivity and detection lower limit of the strain sensor in the prior art. According to the invention, a vertically-oriented three-dimensional two-dimensional material is grown on a mesh substrate through a plasma enhanced chemical vapor deposition system, micro strain is converted into a resistance signal by utilizing the excellent mechanical property and the strain concentration effect of a mesh structure, the resistance signal is converted into a voltage signal through a Wheatstone bridge circuit, the voltage difference between the pre-stretching state and the post-stretching state is calculated, the actual strain is calculated, and the detection of the micro strain is realized.

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

a method for manufacturing a high-sensitivity flexible strain sensor comprises the following steps of growing a vertically-oriented three-dimensional material on a mesh substrate through a plasma enhanced chemical vapor deposition system, utilizing the mechanical property and the mesh structure of the three-dimensional material to enable the sensing material manufactured on the basis of the three-dimensional material on the mesh substrate to generate a strain concentration effect when the sensing material is stressed to cause strain, locally generating obvious structural change to cause the change of a resistance value, converting a resistance change signal of the sensing material into a voltage signal by utilizing a Wheatstone bridge circuit under the strain concentration effect, calculating a voltage difference value before and after stretching, and feeding back the actual strain of the sensing material through the voltage difference value to realize the detection of the micro strain of the sensing material, wherein the flexible strain sensor manufactured by a high-molecular elastic material specifically comprises the following steps:

step 1, a mesh screen is taken as a growth substrate, and the mesh screen is placed in a heating area of a plasma enhanced chemical vapor deposition system after being cleaned;

step 2, placing the substrate material in a heating area of a quartz tube cavity of a plasma enhanced chemical vapor deposition system, adjusting the quartz tube cavity to be in a vacuum state, starting a heating mode of the plasma enhanced chemical vapor deposition system, heating the substrate material in the quartz tube cavity to a preset temperature, introducing precursor gas after the temperature is stable, then starting a radio frequency plasma source, starting deposition, and keeping the temperature and the plasma power stable in the whole deposition process;

step 3, connecting the two ends of the mesh screen obtained in the step 2 with lead-out electrodes, coating a flexible polymer elastic material on the surface of the mesh screen, and connecting two ends of the electrodes with a strain signal processor;

step 4, cutting the mesh screen coated with the flexible polymer elastic material in the step 3, and removing the mesh screen substrate by etching according to the use requirement and the substrate material, wherein if the substrate is a metal mesh screen, the metal mesh screen needs to be removed by etching to ensure the flexibility of the sensing material; if the substrate is a non-metallic stretchable mesh, step 4 is omitted.

Further, the strain signal processor comprises a power module for providing stable voltage, a Wheatstone bridge circuit for detecting resistance change of the sensing material, a signal processing module for amplifying and filtering voltage signals and a signal acquisition module for acquiring signals, reading and displaying, wherein the power module is sequentially connected with the Wheatstone bridge circuit, the signal processing module and the signal acquisition module to form a loop.

Further, the power supply module comprises a button battery box voltage stabilizing circuit.

Further, a flexible strain sensor in a wheatstone bridge circuit is connected between the resistor R1 and ground.

Further, the high molecular elastic material is one or more of polydimethylsiloxane, Ecoflex (copolyester) series silica gel, parylene, polyetherimide, butyl rubber, thermoplastic polyurethane rubber and polyurethane.

Further, the mesh number of the net in the step 1 is 10-300 meshes.

Further, the deposited three-dimensional two-dimensional material in the step 2 is graphene, a carbon nanotube, tungsten disulfide and molybdenum disulfide; the precursor gas is one or more of hydrogen, methane, acetylene and oxygen; the precursor is one or more of molybdenum oxide, sulfur and tungsten oxide.

The invention has the beneficial effects that:

(1) compared with the conventional two-dimensional material sheet layer, the three-dimensional two-dimensional material has a non-stacked form, so that the actual structural strength is unevenly distributed, the stress on a nanometer scale is unevenly distributed in the stretching process, the stress concentration is caused, and the sensitive tension response is generated.

(2) The web substrate used in the present invention imparts a macrostructure that is a three-dimensional two-dimensional material web, as compared to conventional planar substrates. After the original reticular substrate is removed, the stress distribution of the formed reticular hollow structure is changed when the reticular hollow structure is stretched, so that the strain is concentrated in a region with a deeper bending degree, based on the structure, the sensitivity of the strain sensing material manufactured based on the method is improved, and 0.1 per thousand of micro strain can be detected at minimum.

(3) In the invention, the polymer elastic material is coated on the surface of the mesh screen deposited by the three-dimensional two-dimensional material, and after the mesh substrate is removed, a new support is provided for the three-dimensional two-dimensional material, so that the mesh structure is maintained and is not damaged, and the function of protecting the microstructure of the three-dimensional two-dimensional material is achieved. Meanwhile, the mechanical property of the strain sensing material can be improved by compounding the flexible high polymer material and the three-dimensional two-dimensional material, and the strain response in a larger range is realized while the micro-strain detection is realized.

Drawings

FIG. 1 is a copper mesh used in example 1 of the present invention;

fig. 2 is a view illustrating the preparation of a graphene net in example 1 of the present invention;

fig. 3 is a scanning electron microscope image of three-dimensional graphene prepared on a copper mesh in example 1 of the present invention;

FIG. 4 is a flow chart of the signal processing side;

FIG. 5 is a graph showing the step strain response of the strain sensor of example 1 of the present invention in a range of 0.1% o to 0.5% o;

fig. 6 is a graph showing 1% -4% response change in strain sensor elongation in example 1 of the present invention.

Detailed Description

As shown in fig. 1 to 6, the present invention discloses a method for manufacturing a high-sensitivity flexible strain sensor, the flexible strain sensor includes a strain sensing material and a signal processor, the two-dimensional nano material is generally a material whose electrons can only move freely (plane motion) on two-dimensional nano scale, the material has unique electrical and mechanical properties due to the thickness of a single atom, a vertically oriented three-dimensional two-dimensional material is grown on a mesh substrate by a plasma enhanced chemical vapor deposition system, the sensing material manufactured based on the three-dimensional two-dimensional material on the mesh substrate generates a strain concentration effect when being strained by stress, the resistance value changes due to local significant structural changes, and the resistance change signal of the sensing material is converted into a voltage signal by a wheatstone bridge circuit under the strain concentration effect, calculating a voltage difference value before and after stretching, and feeding back the actual strain of the sensing material through the voltage difference value to realize the detection of the micro strain of the sensing material, wherein the flexible strain sensor made of the high polymer elastic material specifically comprises the following steps:

step 1, a mesh screen is taken as a growth substrate, and the mesh screen is placed in a heating area of a plasma enhanced chemical vapor deposition system after being cleaned; the mesh number of the net is 10-300 meshes.

Step 2, the plasma enhanced chemical vapor deposition system comprises four parts: the method comprises the steps of placing a substrate material in a heating area of a quartz tube cavity, adjusting the tube cavity to be in a vacuum state, starting a heating mode of a plasma enhanced chemical vapor deposition system, heating the tube cavity and the substrate material to a preset temperature of 300-900 ℃, introducing precursor gas after the temperature is stable, starting a radio frequency plasma source, starting deposition, and keeping the temperature and the plasma power stable in the whole deposition process.

The deposited three-dimensional two-dimensional material is graphene, a carbon nano tube, tungsten disulfide and molybdenum disulfide; the precursor gas is one or more of hydrogen, methane, acetylene and oxygen; the precursor is one or more of molybdenum oxide, sulfur and tungsten oxide.

Step 3, connecting the two ends of the mesh screen obtained in the step 2 with lead-out electrodes, coating a flexible high-molecular elastic material on the surface of the mesh screen, and connecting two ends of the electrodes with a strain signal processor; the strain signal processor comprises a power module for providing stable voltage, a Wheatstone bridge circuit for detecting resistance change of the sensing material, a signal processing module for amplifying and filtering voltage signals and a signal acquisition module for acquiring signals, reading and displaying the signals, wherein the power module comprises a button battery box voltage stabilizing circuit, the power module is sequentially connected with the Wheatstone bridge circuit, the signal processing module and the signal acquisition module to form a loop, a flexible strain sensor in the Wheatstone bridge circuit is connected between a resistor R1 and a ground wire, and the Wheatstone bridge circuit converts the resistance change into the voltage signals, so that subsequent signal acquisition is facilitated; the voltage signal generated by the Wheatstone bridge circuit of the signal processing module is amplified and filtered to obtain a clearer signal flow;

step 4, cutting the mesh screen coated with the flexible polymer elastic material in the step 3, and removing the mesh screen substrate by etching according to the use requirement and the substrate material, wherein if the substrate is a metal mesh screen, the metal mesh screen needs to be removed by etching to ensure the flexibility of the sensing material; if the substrate is a non-metallic stretchable mesh, step 4 may be omitted.

The high-molecular elastic material is one or more of polydimethylsiloxane, Ecoflex series silica gel, parylene, polyetherimide, butyl rubber, thermoplastic polyurethane rubber and polyurethane.

Example 1:

the embodiment comprises the following steps:

as shown in figure 1, a 50-mesh copper net is taken as a substrate, and the substrate is fully washed by using acetone, ethanol and water in sequence; placing the tube furnace in a heating area in the tube furnace, vacuumizing the tube furnace, and cleaning a chamber of the plasma enhanced chemical vapor deposition system with hydrogen for 5 minutes at a flow rate of 8sccm (standard milliliters per minute) and a temperature of 900 ℃ before the three-dimensional graphene grows; introducing 2sccm of hydrogen and 6sccm of acetylene, starting the radio frequency plasma source after the gas flow is stable, maintaining the power of the radio frequency plasma source at 500W in the whole deposition process, and then starting deposition of the vertical graphene for 60 minutes. After the growth process is finished, the substrate is taken out after the furnace chamber is cooled and cut as shown in fig. 2, silver glue is coated on two ends of the substrate to lead out wires, and the surface of the copper mesh can be observed to be completely covered by the vertical graphene under a scanning electron microscope as shown in fig. 3.

Polydimethylsiloxane is adopted as a coating high polymer material, polydimethylsiloxane colloid is firstly prepared according to the proportion of 10:1 (colloid: curing agent), the surface of the obtained mesh screen is coated, and then the mesh screen is placed into an oven to be thermally cured for 2 hours at the temperature of 80 ℃ to obtain a sensor precursor made of the sensing material. And cutting the sensor precursor to expose the copper mesh substrate, and putting the sensor precursor into a prepared ferric trichloride solution to etch the copper mesh substrate, wherein the concentration is 0.2g/mL, and the etching time is 3 days. And obtaining the high-sensitivity flexible strain sensor after the copper mesh substrate is completely etched.

The flow chart of the signal processing terminal is shown in fig. 4:

the power module comprises a 4.2V button battery and a voltage stabilizing chip, the power supply is divided into two parts, and the first part is used for providing stable 2.5V reference voltage for the Wheatstone bridge circuit. The other part is to provide energy for the signal acquisition module.

The initial resistance of the high-sensitivity flexible strain sensor is different according to different manufacturing conditions, even if the high-sensitivity flexible strain sensor is very slightly strained, the resistance of a three-dimensional two-dimensional material is obviously changed, a fixed value resistance in a Wheatstone bridge circuit is selected according to the initial resistance of the high-sensitivity flexible strain sensor, and the initial resistance values of the high-sensitivity flexible strain sensor and the Wheatstone bridge circuit cannot be too different. In this embodiment, the initial resistance of the high sensitivity flexible strain sensor is 4.1k Ω, so a wheatstone bridge circuit is made up of three 3.9k Ω custom resistors and the flexible strain sensor. When the flexible strain sensor is strained by external stimulus, the resistance of the flexible strain sensor changes. Resulting in a change of the potential difference between the two arms of the wheatstone bridge circuit. Thus, the external strain stimulus is detected and converted into a voltage signal which is changed along with the external stimulus.

The signal processing module comprises a signal amplifying circuit and a filter circuit. The electric signals are transmitted to a signal processing module, an amplifying circuit consisting of an instrument amplifier and a fixed value resistor amplifies the electric signals, and the amplification factor can be regulated and controlled by the resistance value of the fixed value resistor. The amplified electric signal passes through a filter circuit and is composed of an operational amplifier, two capacitors C1 and C2 and two resistors R3 and R4. The filter circuit has a cut-off frequency f, allowing only the electrical signals specific to this frequency to pass,r3= R4=510 Ω, C1=22uF, C2=10uF, with a cut-off frequency of 20 Hz.

FIG. 5 is a graph of the response of the small strain step of the high sensitivity flexible strain sensor made in this embodiment, wherein the percentage change of resistance. When 0.1-0.5 per mill of step micro tensile strain is applied to the high-sensitivity flexible strain sensor, obvious resistance signal change can be observed, and under the condition of keeping the micro strain state for a long time, signals are stable and cannot fall back or suddenly change, so that the sensitivity of the high-sensitivity flexible strain sensor is excellent. Fig. 6 shows the resistance response characteristics over a wide range of strain (1-4%), with the resistance increasing significantly with increasing strain, showing a good linear response.

Example 2:

the embodiment comprises the following steps:

taking a 200-mesh copper net, and fully cleaning the copper net by using acetone, ethanol and water in sequence; the copper mesh was then immersed in 10% hydrofluoric acid for 10 minutes to remove the native oxide layer. The copper mesh was placed in a radio frequency magnetron sputtering system for molybdenum deposition, which was preceded by a 5 minute pre-sputter and then deposited at room temperature for 50 minutes with a distance of 10 cm between the molybdenum target and the substrate holder and a radio frequency power of 150 watts.

After sputtering is finished, taking out the copper mesh substrate subjected to molybdenum deposition, putting the copper mesh substrate into a heating area of a tube furnace, heating the copper mesh substrate in an argon atmosphere, starting plasma (300W) when the temperature is heated to 300 ℃, introducing hydrogen sulfide (20sccm) gas to start a molybdenum disulfide growth process, wherein the growth time is 140 minutes; after the growth is finished, removing the molybdenum disulfide net after the furnace chamber is cooled; silver paste was used to draw the wires out after cutting.

Preparing polydimethylsiloxane colloid: adding a proper amount of polydimethylsiloxane colloid into a measuring cup, and then dripping the curing agent with the mass of 1/10 into the measuring cup. And placing the mixed colloid on a magnetic stirring instrument for fully stirring. And finally, degassing in a planetary stirrer.

And uniformly coating the treated polydimethylsiloxane colloid on the surface of the molybdenum disulfide net after the lead is led out, and then putting the molybdenum disulfide net into an oven to be thermally cured for 2 hours at 80 ℃ to obtain the sensor precursor.

Preparing an etching agent, dripping 1 drop of concentrated hydrochloric acid into 4g of ferric trichloride powder to keep an acidic environment, then adding 20mL of deionized water, and fully and uniformly stirring to obtain the etching agent.

And soaking the sensor precursor in an etching agent for etching for 3 days to finally obtain the high-sensitivity flexible strain sensor.

The flow chart of the signal processing terminal is shown in fig. 3:

the power module comprises a 4.2V button battery and a voltage stabilizing chip, the power supply is divided into two parts, and the first part is used for providing stable 2.5V reference voltage for the Wheatstone bridge circuit. The other part is to provide energy for the signal acquisition module.

The initial resistance of the sensor made of the sensing material varies according to the manufacturing conditions, and in the embodiment, the wheatstone bridge circuit is composed of three 5.9k omega custom resistors and the sensor.

The signal processing module comprises a signal amplifying circuit and a filter circuit. The high-sensitivity flexible strain sensor is connected with the three fixed value resistors and can be placed in front of nostrils or lips to detect human respiration signals, and the gas flow caused by human respiration can drive the sensor to stretch or shrink to form fluctuation electric signals matched with respiration.

The electric signals are transmitted to a signal processing module, an amplifying circuit consisting of an instrument amplifier and a fixed value resistor amplifies the electric signals, and the amplification factor can be regulated and controlled by the resistance value of the fixed value resistor. The amplified electric signal enters a wave filtering circuit which is composed of an operational amplifier, two capacitors C1 and C2 and two resistors R5 and R6. The filter circuit has a cut-off frequency f, allowing only the electrical signals specific to this frequency to pass,r5= R6=750 Ω, C1=22uF, C2=22uF, with a cut-off frequency of10Hz。

The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that modifications and embellishments within the scope of the invention may occur to those skilled in the art without departing from the principle of the invention, and are considered to be within the scope of the invention.