Study On The Flexible Strain Sensor And Its Enlarging Strain Sensing Range Technology Based On Liquid Metal

This paper designs and develops a flexible strain sensor that can realize large strain measurement in response to the large strain measurement needs in engineering.It mainly uses silicone rubber polydimethylsiloxane(PDMS)as the base material and uses Engraving technology engraves micro-channels inside,injects gallium-indium alloy(EGa In)that remains liquid at room temperature into it,using silicone rubber with high elasticity,good flexibility,stable properties,and liquid metal mobility and conductivity Features,to achieve a function similar to flexible "resistive strain gauges".In this paper,the strain sensing structures of single-layer structure and double-layer structure are designed.In the strain sensing structure of the single-layer structure,the micro-channels are in a plane,and a total of 6 sensor chips are designed and prepared according to different design parameters.In order to investigate the sensor characteristics of the sensor chip,a calibration test and a repeatability test were carried out.The test method verified that the sensor structure has the characteristics of high sensitivity,large strain range,small return error and good repeatability.The strain sensing structure in the form of a double-layer structure is formed by bonding upper and lower substrates and middle spacers respectively engraved with micro-channels,and a Wheatstone full-arm working bridge circuit is integrated on the same sensing chip.This paper theoretically demonstrates that this type of design can effectively improve the sensitivity of strain sensors.Through theoretical and experimental arguments,the main conclusions of this article are as follows:(1)Using silicone rubber polydimethylsiloxane(PDMS)material as the base material,by engraving micro-channels inside and injecting gallium-indium alloy(EGa In),the strain sensor prepared by fully utilizing the "flexibility" of the two can be realized The purpose of large strain measurement.(2)Affected by the processing accuracy,even the same design parameters cannot guarantee the same initial resistance of the sensor.The initial resistance of the sensor chip designed in this paper can differ by hundreds of milliohms.Therefore,the initial resistance of the same type of sensor chip needs to be Determined by experimental measurements.(3)The sensing characteristics of the liquid metal flexible strain sensor are affected by multiple design parameters,including the thickness of the sensor chip,the layout of the micro-channels,the cross-sectional dimensions of the micro-channels,and the spacing between adjacent micro-channels.The thickness of the chip has a certain effect on the sensitivity of the sensor chip,but in the case of a difference of 1mm in thickness,the effect is not obvious.Basically,the thinner the chip,the greater the sensitivity.The crosssectional size of the micro-channel has a great influence on the sensitivity of the sensor chip,and the sensitivity of this type of sensor can be effectively improved by reducing the cross-sectional size.The micro-channel spacing is also an important factor affecting the sensitivity of the sensor chip.Experiments have shown that a larger micro-channel spacing can improve the sensitivity of the chip.(4)High temperature has a certain influence on the initial resistance and sensing characteristics of the liquid metal flexible strain sensor chip,and the degree of influence is about the same as that of ordinary metals.In practice,temperature correction is required.(5)The sensing characteristics of the liquid metal flexible strain sensor are affected by multiple design parameters,including the thickness of the sensor chip,the layout of the micro-channels,the cross-sectional dimensions of the micro-channels,and the spacing between adjacent micro-channels.The thickness of the chip has a certain effect on the sensitivity of the sensor chip,but the effect is not obvious when the thickness differs by1 mm.Basically,the thinner the chip,the greater the sensitivity;the cross-sectional size of the micro-channel has a greater impact on the sensitivity of the sensor chip Large,by reducing the cross-sectional size can effectively improve the sensitivity of such sensors;micro-channel spacing is also an important factor affecting the sensitivity of the sensor chip,experiments show that a larger micro-channel spacing can improve the sensitivity of the chip.(6)The sensor structure of the double-layer structure can theoretically increase the sensitivity of the single-layer structure by 2(1+?)times,and the Poisson ratio of polydimethylsiloxane(PDMS)at room temperature is 0.48 The sensitivity can be increased by 2.96 times.In addition,the design also realizes temperature selfcompensation,and effectively reduces the size of the sensor chip.