With the aim of discovering, designing and developing a novel actuator, existing technologies are broken down into
components. These are the material or phenomena that provide mechanical power, the type of stimulus required to
"excite" the technology and the geometrical arrangement, or configuration of the technology to manifest as an actuator.
To date, a number of attempts have been made to classify and compare actuators. Existing comparisons typically use
active material performance as a source for actuator data, even though a material alone is not active. A stimulus
generation must be present for an active material to be used as an actuator and the addition of local stimulus generation
can severely affect the performance of an actuator. Little or no attempt to classify different actuation technologies and
configurations with consideration of the nature and provision of stimulus has been made. By classification of stimulus
and actuator configuration, many further research areas are identified. The structured actuator categorisation along with a
fundamental view of the requirements of an actuator forms the basis of an engineering biased selection strategy.