Actuators are components that are essential to the moving, manipulating, or deforming of objects. Historically, conventional electromagnetic motors as well as pneumatic and hydraulic actuators have been developed to sophistication. In the past several decades, however, many other kinds of actuators based on novel principles have also been proposed. These have employed physical or/and chemical effects, such as piezoelectric, electrostatic, or giant magnetostrctive effects, as well as thermal expansion, phase transformation, or ion mobility in polymers. Not only the novel actuators but also conventional ones have been continually evolving in astounding ways. These actuators have been embedded not only in conventional machines but also in smart ones, such as artificial muscles for robots and power assist systems, electric vehicles, and machine tools. By combining the actuators with the Internet of Things (IoT), they are also used to test equipment. In addition, there is no doubt that the technologies involved in the development of novel actuators and the improvement of their efficiency are key to the achievement of Sustainable Development Goals (SDGs), as actuators currently consume a huge aggregate amount of energy. In sum, actuators have the potential to be central to the development of innovative machines.

This special issue features one review, six research papers, and three technical papers on the most recent advances in various types of actuators. These papers cover topics that include magnetic levitation technologies for precision motion control, electromagnetic motors, fluid power actuators, electrostatic actuators embedded in micro-electromechanical systems, and an ultrasonic motor, plus their applications.

All the papers were refereed through careful peer reviews. I believe that this special issue will help the readers to enhance their understanding and knowledge of actuators and their applications. I would like to express my sincere appreciation to the excellent contributions of all the authors, and I appreciate the incisive efforts of reviewers in producing this special issue.