Variable stiffness and fast-response soft structures based on electrorheological fluids

Soft robots have drawn a lot of attention due to their soft materials that make them highly flexible and adaptable to complex environments. However, these also make soft robots not suited to high-load tasks, and achieving controllable material stiffness variation is still a challenge. Herein, we designed a soft structure with variable stiffness based on electrorheological fluids, which presented the advantages of continuously variable stiffness and fast response. The structure exhibited a stiffness of up to 1065 mN mm(-1) when the electric field strength was 4.5 kV mm(-1) (displacement of 1 mm). When varying the electric field strength (0 to 4.5 kV mm(-1)), the rate of stiffness variation was over 1500%. According to the load cycle experiments, it was shown that the structure's response time to a change in load was less than 65 ms, and that the structure changes could be made repeatedly. In addition, we demonstrated the functions of stiffness adjustment, shape memory, and motion locking of the structure. This work has potential applications in the fields of soft robotics and artificial muscles.