| The e-skin is a popular research direction in flexible electronic technology.It attaches a flexible substrate to the surface of an object closely,restores the sense of touch and proximity through an integrated pressure sensor,and can achieve the purpose of simulating human skin.Compared with the rigid substrate used in traditional electronic technology,the e-skin is lighter and more flexible,and can be attached to the surface of the detection object to adapt to various shapes.It has greater research prospects in the fields of biomedicine,humancomputer interaction,and wearable devices.In the previous research of this research group,a three-dimensional force-capacitance sensor used in rehabilitation robots was proposed.However,in the actual application process,it was found that the background capacitance of the sensor was only about 0.2 p F,and the amount of change remained at a few f F.This technical parameter puts forward extremely high requirements on the accuracy of the measurement circuit,and the current measurement circuit presents a huge challenge for this order of magnitude measurement.In response to the above problems,this thesis improves the dielectric properties of the flexible dielectric material in the sensor by doping the carbon-based conductive filler into the PDMS flexible base material,thereby improving the sensitivity of the sensor.First,the influencing factors of the dielectric properties of the material are introduced,and the preparation process of the composite material is introduced.Next,design experiments to compare and analyze the influence of the mixing ratio and filling concentration of carbon nanotubes and carbon black on the dielectric properties of the flexible material,and determine the optimal mixing ratio and filling concentration.Then,study the manufacturing process of the sensor and prepare the sensor samples,and build the test platform of the threedimensional force microcapacitance sensor.Finally,the static characteristics of the sensor are compared and analyzed through experiments.The experimental results show that when the filling ratio of carbon-based filler is 3wt % and the mixing concentration of carbon nanotubes and carbon black is 2:1,the obtained flexible composite dielectric material can have the characteristics of high background capacitance and high sensitivity.Compared with the original sensor,in the positive pressure direction,the background capacitance of the sensor increased from 262 f F to 1.676 p F in the pressure range of 0 ～ 30 N,which was 6.40 times the original,and the sensitivity increased from0.45 f F/N to 70.2f F/N is increased by 156 times,linearity is 9.98%,hysteresis is 9.26%,repeatability error is 1.72%.In the direction of shear force,the sensor’s background capacitance value is increased from 226 f F within the shear force range of 0 ～ 15 N To 1136 f F,an increase of 5.03 times,the sensitivity from 0.2Ff/N to 3.27 f F/N,an increase of 16.35 times,the linearity is 11.51%,the hysteresis is 18.37%,and the repeatability error is 2.63%.The research results of this article can reduce the difficulty of measuring circuit detection and improve the accuracy of measurement data.Using the prepared flexible composite material as the dielectric layer of the capacitive sensor can effectively improve the measuring range and sensitivity of the sensor.The flexible dielectric material in this article can be used as a reference for biomedicine,wearable devices and other fields,and has practical value and application prospects. |
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