Twist–coil coupling fibres for high stroke tensile artificial muscles

•A new type of tensile artificial muscle is introduced for the first time.•The muscle consists of a torsionally-active fiber that is serially connected to an elastomeric fiber.•Heat induced untwist of one fiber causes coil formation and shortening of the second fiber.•Large contraction strains of more than 10% are demonstrated.•A comprehensive mechanics model is developed that accurately describes the new actuation mechanism.