The evolution of mechanical actuation: from conventional actuators to artificial muscles

Mechanical actuators are defined as mechanical devices that convert an input energy into motion. Since the 1990s, advancements in the fields of robotics and automation have produced a critical need for the development of lightweight and efficient actuators capable of human-like motion. In the past few decades, extensive research activities in the fields of materials science and smart materials have led to the development of a novel type of actuator known as artificial muscles. This review paper describes the evolution of mechanical actuators from conventional technologies such as electric, hydraulic, and pneumatic actuators, to bioinspired artificial muscles. The working mechanism, manufacturing process, performance, and applications of different artificial muscles are described and compared with those of conventional actuators. Details on the cost, input sources, activation modes, advantages, and drawbacks of each artificial muscle technology are also provided to guide the reader through the intricate selection process of the best-suited actuator for a specific application.