Structured Design,Properties Study And Finite Element Analysis Of Conductive Elastomer Composites For Force-Sensitive Sensing

With the rapid development of science and technology and the improvement of human life,flexible wearable electronic sensors and artificial intelligence devices have become the priority of national development,which have attracted enormous research attention.Conventional silicon-based electronics suffer from the lack of flexibility,which limits their application in comfortable wearing.Flexible wearable electronic sensors capable of sensing external pressure stimuli and transforming it into detectable current variations,have been widely concerned for their versatile potential in human healthcare detection,intelligent electronic skins,smart medical diagnosis,and human-machine interfacing.However,it is still challenging for the mostly reported flexible electronic sensors to simultaneously achieve high sensitivity,broad sensing range,reliable cycling stability and multifunction,which cannot meet the requirements in full-scale personal healthcare monitoring.Therefore,it is highly expected to develop a multifunctional flexible electronic sensor featuring excellent wearing comfort and outstanding sensing performance,which hold great promise in healthcare monitoring,intelligent human-machine interaction,smart personal protection and next-generation artificial skin.Hence,this study focuses on the design and development of the multifunctional flexible electronic sensors with excellent sensing performance and comfortable wearing from the design of polymer matrix materials,the preparation of the conducting materials,the fabrication of the conductive composites and the assembly of the flexible electronic sensors.（1）Traditional flexible electronic sensors are incapable of high sensitivity and broad sensing range simultaneously,which limits their application in full-scale human healthcare detection and intelligent medical diagnosis.Herein,a three-dimensional（3D）network-like conducting composite and device were designed.First,graphene oxide and MXene were assembled,which was followed by blending with rubber latex and by further reduction of graphene oxide to obtain 3D conducting network-contained composites.Finally,the conducting composite was assembled with the interdigitated electrode to obtain the flexible wearable electronic sensors.The assembled sensor exhibited a high sensitivity(up to 94.13 k Pa^-1),ultrabroad sensing range（444.4 k Pa）,which enable full-scale human motions monitoring,possessing great potential for electrophysiological signals detection,human health monitoring,intelligent medical diagnosis,and artificial electronic skin.（2）Common flexible electronic sensors are fabricated from airtight elastomers or dense plastic films,which will block the efficient permeability of volatile compounds,resulting in the decreased long-term comfortable wearing.Bioinspired by 3D network structure of ant nest,a wearable,breathable,and biodegradable electronic sensor is prepared from facile face-to-face assembly of breathable biodegradable three-dimensional conductive MXene-coated poly（1,8-octanediol-co-polycaprolactone citrate）elastomer composite（MXene@POPLC）templated from porous sugar cube,and an MXene ink-printed interdigitated electrode-coated breathable electrospun film.The as-obtained flexible electronic sensor exhibits high sensitivity(up to 246.3 k Pa^-1),broad sensing range（up to 333.3 k Pa）,reliable cycling stability（～20,000cycles）,fast response（10 ms）/recovery（11 ms）time,robust breathability,excellent biocompatibility,and facile biodegradability,which can be employed for ultrasensitive personal healthcare monitoring,and wireless wearable human-machine interfacing by combination with wireless transmission device,holding great promise in smart healthcare monitoring,intelligent human-machine interaction,smart personal protection and next-generation artificial skin.（3）There is a lack of systematic analysis on the design and sensing mechanism for conductive composites with 3D structure.Herein,the force-sensing mechanism of the 3D network conductive composite was studied by equivalent circuits and formulas.The determined factors for the sensitivity are the initial resistance of the sensor,the resistance change of the conductive composite and the contact resistance change between the conductive composite and the electrodes under external pressure.The effects of pore size,modulus,and thickness of 3D network conductive composites on the sensing performance was investigated by finite element analysis.This work illustrated the sensing mechanism of the conductive network structure,providing a theoretical basis for the design and preparation of 3D network conductive composites and devices with excellent sensing performance.Moreover,the surface microstructure of the force-sensing material had been demonstrated to obviously improve the sensing performance of sensors.Herein,the conductive paths and simulated circuits were employed to study the evolution of the resistance and the sensing mechanism of the sensor with different surface morphologies.Finite element analysis was employed to simulate the morphology,stress concentration and contact area changes of surface microstructures under external pressure.This study established a theoretical foundation for the development of conductive composites with different surface microstructures.