Research On Sensing/Actuating Coupling Performance Of Magnetorheological Elastomer

Magnetorheological elastomer(MRE)is a kind of smart material composed of ferromagnetic particles and polymer matrix.Different from the traditional liquid matrix and plastic matrix,MRE shows excellent mechanical behavior and stable structure due to its high elasticity.Because the magnetic particles in the MRE matrix can be magnetized under the external magnetic field and interact with the rubber matrix,its stiffness,damping,storage modulus and other mechanical properties can be adjusted in real time under the magnetic field.Therefore,the unique mechanics-magnetic coupling performance of MRE makes it widely used in vibration control fields such as dampers and absorbers.Among them,the multi field coupling behaviors of MRE,such as mechanic-electric,magnetic-electric,present broad prospects in the smart sensing field,so the research on the electrical properties of MRE has gradually become an important research direction.Recently,many scholars have carried out the preliminary performance research and application exploration on flexible sensors based on MRE.The sensing response of conductive MRE under external stress stimulation such as tension and compression has already been analyzed,and the deformation behavior of MRE under the action of magnetic fields has also been explored.However,the research and application of the actuate-sensing coupling behavior of conductive MRE are still scarce.Aiming at the current research status of the actuating-sensing coupling behavior of MRE,by designing and developing conductive MRE with different shapes and structures in this paper,and systematically investigates the relationship between the microstructure and the mechanic-electric coupling performance of conductive MRE.The response characteristics of conductive MRE under external mechanical stimulation are analyzed,and the behavior of conductive MRE under magnetic field actaute-sensing real-time monitoring feedback is further studied,and the multimodal actuating mode of conductive MRE is also explored.At last,the multi-functional smart soft MRE actuating device is constructed.The main research contents are as follows:1.Structural design and properties study of natural fiber mechanically enhanced MRE.In this study,a high-performance natural fiber mechanicallyreinforced MRE is proposed.Its mechanical properties are actively controlled by a 3D topological structure composed of vertically interacting natural fibers and carbonyl iron particle(CIPs)chains.The effects of CIPs content,fiber layer number,crosslinking ratio,curing time and pre-structure on the mechanical properties of MRE were systematically studied.By adding two layers of natural fibers into the MRE matrix,the tensile strength of the MRE matrix was increased by 87%.When the content of magnetic particles is 70 wt%,the magnetorheological effect of fiber reinforced MRE is 184%.Based on this 3D structure MRE,the magnetic soft gripper is designed and developed.The free closure and spatial position movement of the gripper are realized through the portable micro-magnetic field.The flexible MRE sensor is attached on the gripper surface,which can in-situ monitor the close-open behavior of MRE gripper,and the magnetic actuate-sensing monitoring function of the MRE soft gripper is realized.2.Research on the coupling behavior of bending sensing and magnetic actuate based on natural fiber enhanced MRE.In order to realize the self sensing of MRE magnetic actuate response,this work developed a one-dimensional linear coaxial fiber piezoresistive sensor with silver nanowire coated with natural fiber as the conductive core and MRE as the packaging shell.Due to the high non-tensile performance of natural fiber,the MRE fiber sensor can be used to monitor the bending mechanical excitation directionally.By designning different shapes and structures of MRE packaging shells,the actuating application of MRE fiber sensors in complex environments is realized.When the external magnetic field density increases from 40 mT to 80 mT,the relative resistance change(ΔR/R0)of the MRE fiber sensor increased from 8.9%to 15.9%,and the magnetic actuate-sensing coupling is realized.Based on the weave-ability of natural fibers,the MRE fiber array sensor with 3D fiber network structure can be constructed,which is expected to be applied to flexible smart wearable clothing.3.Mechanism analysis and magnetic actuate application exploration of MRE sensing films with bending and tension discriminating detection.In order to decouple the response of MRE sensors to different external stimuli and recongnize them,this work developed a sandwich structure film sensor based on MRE and silver nanowires is developed,which can distinguish the tensile and bending mechanical excitation by providing opposite electrical signals.When the tensile strain is 37.5%and the bending displacement is 5 mm,the ΔR/R0 of MRE sensor reached 1064.5%and18.2%,respectively.The highest tensile and bending gauge factor reaching 66.7 and11.2%mm-1,respectively.Spin-coating technology endows the film sensor with adjustable thickness characteristics,so it can be used as an electronic skin to monitor human motion and realize the application of MRE in the sports health and smart monitoring field.Based on the non-contact magnetic actuate behavior of MRE,the smart magnetic control keyboard is designed and developed,which expands the application of MRE film sensor in artificial intelligence(AI)devices.4.Research on magnetic-electrothermal dual mode actuating and sensing properties of MRE films.In order to further improve the actuating efficiency and controllability of conductive MRE actuators,this work developed a smart dual-modal actuator based on MRE by choosing conductive materials with ultra-high conductivity to realize contact electrothermal actuate and non-contact magnetic actuate.At 2V applied voltage,the bend angle of MRE actuator can reach 219.3°.Using the finite element method to establish a theoretical model,it is calculated that the deflection displacement of the MRE actuator at 60 mT is 13.8 mm,which is close to the experimental deflection displacement value of 14.7 mm.The theoretical calculation results and experimental results could confirm each other,thus further guiding the structural design of the MRE actuator.Notably,this MRE actuator shows the electrothermal and magnetic dual mode actuating function,which can be further applied to the customization and diversified design of smart bionic robots.5.Research on the design and application of multifunctional MRE soft pipeline that integrates sensing-actuating-electrothermal.In order to further expand the application of MRE soft actuators in the AI field,this work designed and constructed an in-situ self monitoring MRE magnetic actuate soft pipeline.The sensing and electrothermal films constructed from silicone rubber matrix were respectively attached to the top and bottom of the MRE soft pipeline,the functionals of electrothermal heating of the MRE soft pipeline,and real-time sensing of the transportation process were realized.The ΔR/R0 of the MRE soft pipeline under 4 mm compressive displacement is 143.3%,and its ΔR/R0 under 55 mT magnetic field density is 40.8%.By continuously applying 0.6 V voltage to the electrothermal film,the temperature of the MRE soft pipeline can rise from 26.7℃ to 38.1℃ within 1 min.Once transport colored ink time of this MRE magnetical actuate soft pipeline is only 0.8 s,and the ΔR/R0 of this pipeline under magnetic actuating is 28.5%.The design of multifunctional MRE soft pipeline devices has promoted the application and development of MRE actuators in the biomedical field.