A Bistable Artificial Muscle Actuator

We present an artificial muscle actuator based on the axially compressed buckled beam of bending actuator material. Thus natural bistable structure helps to overcome some problems found in the new materials used for artificial muscle actuators, such as relaxation and non-repeatability. Without electrical stimulation the buckled beam remains in one of two stable positions. Actuating the structure causes it to switch from one state to the other, thus giving a versatile element that can be used as an actuator, mechanical switch or adjustable structural element. The structure can be partially actuated in order to move the actuator with respect to one of the stable states without actually switching state. Likewise a variable force can be generated. We show how initial study of the standard buckled beam model suggests a method for segmenting bending actuator materials such as ionic-polymer metal composites (IPMC) in order to switch between states through low energy paths. We also show how such a structure can be used to construct a cilium-like actuator that generates the standard envelope of power stroke and recovery stroke using a one-degree of freedom input