Optimization And Performance Evaluation Of Flexible Capacitive Sensor Prepared With Conductive Silicon Rubber

With the rapid development of science and technology,flexible sensor has received extensive attention because of its huge application potential in field of human-computer interaction and smart wearables.Flexible capacitive sensor is characterized with short response time,high sensitivity and strong reliability which guarantees its broad application prospects in artificial intelligence.This research mainly focuses on the fabrication of flexible capacitive sensor（FCS）with a conductive silicon rubber（CSR）film as its basic material.The prepared FCS was systematically studied and evaluated in aspects of composition,structure,preparation process,performance and practical application.The composition for preparing the CSR film was determined,and the three-layer structure of the FCS was prepared by an optimized spraying process with surface microstructure introduced.The basic performance of the sensor and the response capability and reliability to applied load were tested.Final response test verified its application potential in the field of electronic skin and human-computer interactionCSR and polydimethylsiloxane（PDMS）films were selected as the electrode（e-）and dielectric（d-）layers of the FCS,respectively.The CSR was consisted of 35 wt%carbon fiber as conductive filler,25 wt%dimethyl silicone oil as diluent and 5 wt%of 1,2-propylene glycol plasticizer.The CSR film prepared by spraying process showed good conductivity and mechanical properties which made it suitable as an electrode layer material for FCS.Microstructures designed on the surface of the e-and d-layers of the FCS effectively improved its sensitivity.The sensor adopted generally a sandwich structure with CSR as its upper and lower e-layers and pure PDMS as the middle d-layer.Microstructures were introduced on the surface of e-and d-layers with aids of surface replica,which made the sensitivity of the FCS up to 0.82 k Pa^-1.The surface microstructure was quantitatively characterized with roughness.The fabricated FCS by optimized spraying process exhibited good consistency in initial capacitance.Based on the spraying process in the laboratory,parameters including spraying distance,spraying pressure,gun caliber and spraying angle were determined.PDMS and CSR films were obtained with good mechanical properties and a uniform thickness of about150-200μm.The initial capacitances value of all FCSs with surface microstructure were kept about 15-17 p F.The prepared FCS responded stably to various applied loads.In the load range of 0-5 k Pa,sensor C-P400 exhibited the highest sensitivity,small response hysteresis to single-cycle compression-recovery load,stable and reliable response to multi-cyclic tensile,bending and compression loads.The FCS array was capable to detect the spatial distribution of load.With help of Arduino,two designed FCS arrays in 2×2 and 3×3 could control the corresponding LED arrays and realize the detection of spatial pressure distribution.The FCS was also capable to detect movements of walking,arm bending and fist as well as computer information input by attaching to gloves,indicating its bright future in human-computer interaction.