a temperature - controlled actuator has a housing with a proximal end and a moveable distal portion . a core - wire extends along the housing , with its distal section anchored to the distal portion of the housing . the core - wire &# 39 ; s distal section has an austenite state and a martensite state . the distal section moves the distal portion by transitioning between the austenite and martensite states in response to a temperature change along a thermometric section of the core - wire . a proximal section in mechanical communication with the core - wire &# 39 ; s distal section transmits tension , provided by a tensioning element , to the distal section . the tensioning element , which is coupled to the proximal section of the core - wire , constantly applies a tensioning force to the core - wire .