Shape memory alloy actuation apparatus

A shape memory alloy actuation apparatus comprises a movable element supported on a support structure by a suspension system comprising a plurality of resilient flexures. A shape memory alloy actuator drives movement of the movable element on contraction. An end-stop limits the movement of the movable element in the opposite direction. Rather than using the resilient flexures of the suspension system as the sole biassing means, an additional Massing element biasses the movable element against the SMA actuator. When the moveable element is held against the end-stop, the force applied by the biassing element is greater than the force applied by the flexures of the suspension system. This reduces the design constraints, for example allowing a greater range of movement.