Conductive magnetorheological fluid (cMRF)-based flexible sensor with adjustable stiffness for magneto-mechanical dual-response and soft actuator

Traditional flexible electronic sensors based on rigid conductive materials are prone to damage to the conductive network due to the modulus difference between them and the elastic substrate. In this work, using the "filling and sealing" process, we develop conductive magnetorheological fluid (cMRF) filled Ecoflex soft elastomer composite (cMFEC) based on liquid conductor by encapsulating cMRF into Ecoflex substrate. Due to the conductivity and magnetorheological effect of liquid conductor cMRF, cMFEC not only possesses the tensile sensing performance and perception ability of bending angle of conventional flexible sensors, but also manifests magnetic response properties with magnetic induced stiffness enhancement and magnetic actuation behavior. By assembling cMFEC with 3D-printed ABS structures, the variable stiffness load-bearing platform and intelligent magnetic actuated gripper are fabricated. The variable stiffness load-bearing platform shows that cMFEC has the magnetic induced stiffness enhancement characteristics. The magnetic actuated gripper can grasp, transfer, and release objects with various shapes under the control of the magnetic field of the permanent magnet, and the process can be monitored by its own electrical properties. This work provides a simple strategy for manufacturing multi-functional sensors based on liquid conductors. It can be expected that this kind of sensor based on cMRF will be a promising candidate in flexible electronic sensor.