An actuator for a component such as a valve or pump comprises a chamber or capsule (30) of a flexible material, which chamber or capsule (30) is mounted on a substrate (18). Within the capsule (30) is a quantity of thermopneumatic material (32) (i.e. material which expands in volume upon heating). Also disposed within the capsule (30) is an infrared radiation absorbing layer (16). In use, infrared radiation is applied to the capsule (30) at or close to the location of the infrared radiation absorbing layer (16), thereby causing the thermopneumatic material (32) within the capsule (30) to be heated. As the thermopneumatic material (32) is heated, it expands in volume and causes movement of the flexible material forming the capsule (30), i.e. it causes mechanical movement thereof. As the thermopneumatic material (32) cools, it returns to its original volume and the flexible material of the capsule returns to its original position accordingly.