Fabrication And Characterization Of Flexible Pressure And Strain Sensor Based On Screen Printing

In recent years,graphene-based pressure/strain sensors have received intense attention in the field of wearable devices.However,how to manufacture low-cost,reliable and stable graphene electrodes that can be used for flexible sensors in large scale is still a challenge.Based on this,graphene ink for screen printing made from laser-induced graphene（LIG）can be printed on various substrates with any shape of electrodes needed using screen printing technology.In the study,flexible pressure and strain sensors were prepared using screen printing technology,and the performance and practical application of the sensors were studied.First,graphene is induced from Kapton PI tape by certain energy of CO₂laser and combined with screen printing technology to print electrodes for flexible pressure/strain sensors.Screen printing technology is a convenient,efficient and low-cost way for fabricating electrodes.In the screen printing process,the proportion of LIG ink and the mesh count of the screen printing plate for printing the electrode pattern are two key parameters that affect the performance of the flexible sensor.By testing and comparing flexible strain sensors made from LIG ink with different proportions,the ratio of graphene powder,DBE solution,and trichloroacetic acid resin is determined to be 9:2.5:1.Through research,a mesh count of 100 is selected for the screen printing plate.Second,flexible LIG pressure sensor was fabricated by combining two electrodes face to face which were made by screen printing on PDMS substrates.The sensing mechanism of the pressure sensor was investigated by SEM analysis of the section view of electrodes.As is shown in the performance tests,the as-fabricated pressure sensor performs high sensitivity(～1.84 k Pa^-1),very low detection limits（3.4 Pa）,super fast response and recovery time（2.7 ms and 4.5 ms perspectively）,and good duranbility（over 2000 circles）.Besides,through practical application tests,it is demonstrated that the LIG flexible pressure sensor has promising potential for application in wearable devices.Last,flexible LIG strain sensor was fabricated by screen printing rectangular electrode on PDMS substrate and packaging it with PDMS solution.The sensing mechanism of the strain sensor was studied by SEM analysis of the surface of the electrode.The as-fabricated strain sensor shows high sensitivity（gauge factor=96 under strain of 0～13%）,very fast response and recovery time（0.25 s and 0.29 s respectively）and excellent durability（over 1000 circles）.Moreover,practical application tests are carried out to prove its application value in human wearable devices.In this work,LIG（Laser-Induced Graphene）electrode using screen printing technology is prepared,which exhibits high sensitivity,fast response and recovery time,and good durability for use in flexible pressure/stress sensors.It has great potential for applications in wearable electronic products and personal health monitoring.Additionally,the graphene ink developed in this study for screen printing opens up avenues for low-cost,large-scale production of patterned graphene electrodes for other micro-nano devices.