Development And Performance Research Of Magnetorheological Elastomer Based Flexible Sensing Devices

Magnetorheological elastomer(MRE)is one kind of intelligent material composed of magnetic particles and polymer matrix.By controlling the external magnetic field,mechanical properties of MRE can be continuously,rapidly,and reversibly changed,exhibiting a unique magnetorheological effect.In the past two decades,through optimizing polymer matrix,magnetic particles,additives,etc.,the mechanical properties and magnetorheological effects of MRE have been greatly improved.Recently,the electrical performance of MRE has become an emerging research hotspot in this field.The special mechanic-electric and magnetic-electric characteristics make MRE possess great implement potential in intelligent sensing field.At present,although some progress has been made in the experimental testing and theoretical analysis of conductive MRE,a lot of further research works are still needed to develop MRE-based highly sensitive sensing devices which have excellent magnetic-magnetic-electric response performance.In this paper,by designing and optimizing the structure and preparation process of MRE,high-performance conductive MRE with different structures have been developed.The characterization methods of MRE sensors have been studied in depth.The relationship among electrical properties,micro-structures of MRE,and excitation fields has been explored.The applications in non-contact sensing devices,and bionic robots,and human-computer interactive electronics have also been investigated.The main research contents are as follows:1.Novel resistive MRE sensors with different dimensions have been developed.This research focuses on designing structure,as well as optimizing material parameters and manufacturing processes,such as matrix vulcanization ratio,carbonyl iron particle mass fraction,conductive materials and their mass fractions,to obtain MRE sensors with high flexibility and sensitivity.Low-density porous structure,one-dimensional fiber structure,self-assembled contact-type interlocking structure,and three-dimensional structure have been designed to solve the existing problems of flexible MRE sensors,such as insufficient flexibility,low sensitivity,and complicated preparation processes.2.The experimental methods and magnetic-mechanic-electric performance of flexible MRE sensors under external stimuli have been investigated.Rheometer,electrical performance test system,micro/nano mechanical test system,magnetic system,and self-made devices are used to analyze and evaluate mechanic-electric performance of MRE sensors under tension,compression,bending,torsion,shear,out of plane force,and magnetic field.The magnetic-mechanic-electric response under different experimental parameters has also been studied,such as threshold,sensitivity,linearity,response time,and stability.Hereinto,the parameters include magnitude of forces,different magnetic field environments,magnitude and applied direction of magnetic fields.Research results show that MRE sensors can distinguish the mN-level force changes and mT-level magnetic flux density changes via structural design.The strain sensitivity could reach to 1965,and the stress sensitivity reached 1.7%Pa-1.The magnetic field sensitivity GFm reached 240%T-1.3.Using finite element simulation and other numerical methods,the magnetic-mechanic-electric response mechanisms of MRE with different structures under external forces and magnetic fields have been explored.The electrical performance of MRE sensor is controlled by electrical properties of network components and a combination of conductive network morphology.Combined with the micro-structure parameters such as interface characteristics,the relationship between the evolution of micro-structure and the changes in the mechanic-electric properties has been analyzed.Validated with experimental results,a theoretical model describing the magnetic-mechanic-electric behavior is established.4.The potential applications of flexible MRE sensors in intelligent fields have been investigated.Flexible MRE sensors possess bionic functions,such as sensing micro-force/strain,the flow fields,the magnetic field changes,and sound waves.Based on the performance research of MRE,magnetic switch,flexible magnetic gripper,dual-mode smart checkerboard,sensitivity-settable strain sensor,and non-contact gesture electronics were fabricated.The convenient manufacturing processes and excellent multi-mode sensing characteristics allow flexible MRE sensing devices to have a place in the next generation of intelligent electronics,such as multi-mode sensing systems,non-contact actuating and sensing systems,and bionic robots.