a housing;

a chamber within the housing;

a working fluid changing phase upon heating and located in the chamber;

an electrical heater disposed within the chamber for heating the working fluid upon application of electrical power to the electrical heater;

a piston rod slidably disposed in the housing and movable between a retracted position, retracted with respect to the housing, and an extended position extending outward of the housing, the piston rod being driven and sliding from the retracted position to the extended position in response to heating of the working fluid by the electrical heater;

a first spring biasing the piston rod toward the retracted position;

an electromagnet disposed at an end of the housing and generating a magnetic field when an electric current is supplied to the electromagnet;

a ferromagnetic target assembly attached to the piston rod, sliding within the housing, and attracted toward the electromagnet, when an electrical current flows through the electromagnet, to maintain the piston rod in the extended position even if electrical power is no longer applied to the heater, wherein the ferromagnetic target assembly includes

a ferromagnetic core to which one end of the piston rod is attached, the ferromagnetic core sliding within the housing, and

a guide pin attached to the ferromagnetic core and extending from an end of the ferromagnetic core opposite the end of the ferromagnetic core from which the piston rod extends;

a rolling diaphragm driven by the working fluid; and

a piston contacting and driven by the rolling diaphragm and sliding within the housing upon expansion of the working fluid, the piston including a hollow portion receiving the guide pin.