Actuators are control elements that are electrically operated and provide mechanical energy or power at their output. In technical systems and processes, they are used for the targeted adjustment of energy flows or mass and volume flows. Well-known examples include electromagnetic actuators as well as actuators based on pneumatic or hydraulic principles, which have been used as conventional actuators in various applications for many decades. This book is dedicated to so-called unconventional actuators, meaning actuators that are based on principles other than those mentioned. Some of them have only recently crossed the threshold for large-scale use, while others are on the verge of doing so. In any case, engaging with these modern control elements is worthwhile, as they offer entirely new possibilities due to their special properties.