The invention provides an actuator having a wedge shaped member arranged to move in substantially linear reciprocating motion. A drive member is operatively coupled to the wedge shaped member. The wedge shaped member is arranged to deflect the drive member as the wedge shaped member moves. A shape memory material has a first end electrically connected to a first electrical connection terminal and fixed with respect to the first electrical connection terminal, and a second end electrically connected to the wedge shaped member and fixed with respect to the wedge shaped member. The wedge shaped member is electrically connected to a second electrical connection terminal. The actuator may be used in a pump having a pumping chamber with a membrane the displacement of which changes the pumping chamber volume. The drive member of the actuator is operatively coupled to the pumping chamber membrane. The pump may be used in an infusion system for the infusion of a liquid therapeutic product.
