japanese toki corporation develops biometal fiber, a thin fiber-like metal actuator [driving unit] which acts like a muscle.
although soft and pliable like a nylon thread under normal conditions, it becomes stiff like a piano wire and sharply contracts when a current is fed through it. if the passage of current is stopped, it will soften and extend to its original length. it can be repeatedly moved any number of times. the same effect can be obtained by heating it by hot air.
biometal is a metal-based artificial muscle made of a shape-memory alloy, unlike other artificial muscle systems that are rubber-based [pneumatic pressure-driven] [ 1 ] or chemicals-based [high polymer] [ 1 ][ 2 ][ 3 ].