Fig. 3. Bistability for amplified force and fast response.

Comparison of mechanical performances between the bistable hybrid actuator (blue color) and its two bistability-disabled counterparts: a soft actuator without both linkages and springs (yellow color) and a hybrid actuator without springs (red color). (A) Tracking of the bended shapes at two stable states. (B) Dynamic blocking forces at different blocked bending angles. Insets are schematics of front views of the three actuators. (C) Dynamic blocking force as a function of spring pretension. All the actuators in (A) to (C) are pressurized at 20 kPa. (D) The response time of achieving the largest bending angle for three bistable, hybrid, and soft actuators with different spring pretensions under the same actuation. All actuators are pressurized at 30 kPa with the same flow rate of 3 liters/min. For bistable ones, the response time is composed of two parts including before (highlighted by blue color) and after snapping-through (highlighted by pink color). (E) Finite element simulation results on the actuated switch between two stable states of the bistable hybrid actuator through pressurization.