Design Of Microstructure Of Dielectric Layer Of Flexible Capacitive Pressure Sensors

The capacitive pressure sensors are widely applied in the field of artificial intelligence and medical examinations due to the advantages of high sensitivity,large dynamic response range and fast response.An effective approach towards improving the linearity performance of capacitive pressure sensors is the judicious design of microstructure of the elastomer.COMSOL Multiphysics is widely used to study the capacitance change of the sensor,but the software is difficult to simulate the large deformation and non-linear contact problems.As a result,the deviation of the simulation result from the experimental data is large.Here we develop a method by combining the advantage of both COMSOL Multiphysics and ABAQUS,employing ABAQUS in the mechanical analysis and adopting the traditional COMSOL Multiphysics to simulate the capacitance of sensors on external pressure using finite element analysis method,and our calculated results achieve high conformity with experimental results.To improve the performance of the capacitive pressure sensors,by changing geometrical and material parameters of the microstructure,we can compare and analyze the simulation results.The sensitivity and the nonlinear error of the designed sensors are analyzed.The results from simulation calculation could be used as theoretical guidance in improving performance of sensors.The effect of geometrical and material parameters of the pyramidal microstructure such as the elastic modulus E,length of hemline L,sidewall angle ?,height H and scaling ratio M,on sensitivity and linearity of sensors in different measuring pressure ranges(2 kPa,5 kPa,20 kPa)was investigated using the finite element method.It was found that the sensitivity is more sensitive to E and M,and less sensitive to H and L;the linearity are more sensitive to ?,and less sensitive to H and L.With increasing E,H,? and M,the sensitivity and the nonlinear error decrease.However,the sensitivity and linearity can be improved simultaneously by decreasing L.The effect of geometrical and material parameters of the cylindrical microstructure such as the elastic modulus E,radius R,height H and distance between midpoint of generatrix of the cylinder D was investigated.Due to the slender characteristics of the microstructure,aside from the linearity and sensitivity of the sensor,it is necessary to check the stability of the sensor through the critical load and determine its measuring pressure range.It was found that the sensitivity is much sensitive to R and E.With increasing R and E,the sensitivity decreases greatly.With increasing H and D,the sensitivity change insignificantly.All of the cylinders-based sensors have high linearity.With increasing E and R or decreasing H,the sensitivity increases but the measuring pressure range decreases.The effect of geometrical parameters of the conical microstructure on sensitivity and linearity of sensors in different measuring pressure ranges was investigated by changing the outline or the inner hollow cone of the cone.It was found that for a conical microstructured capacitive sensor,the increase of the size of the inner hollow cone can increase the linearity and sensitivity of the sensor simultaneously.Changing the shape of the inner hollow cone has marginal effect on the linearity and sensitivity of the sensor.Design of outline can increase the sensitivity and linearity of the sensor in 2 kPa and 5 kPa range simultaneously.The results of this study can provide guidance for the design of the microstructures of capacitive sensor.