Actuators Based on Hydrogels

Abstract

Many electronic actuators of different dimensions, such as motors, relays, pumps, and mixers, have evolved rapidly, and many are commercially available. Its application into soft environments such as biological tissues is desirable to develop automated biomedical devices. However, they present innate difficulties. Limitations are mainly due to its structural rigidity and chemical composition. To address this need, soft‐actuators are under development. These devices have great mechanical and chemical similarity with biological tissues and, as a consequence, many have a high biocompatibility. Soft‐actuators are capable of mimicking the behavior of muscles or other tissues that are involved in locomotion in biological organisms. Most of them are hydrogels which are polymers structured in three‐dimensional networks, capable of harboring large amounts of water. Hydrogels can reversibly change its volume up to 50, 100 times, or more, from a dried or collapsed state to a hydrated state. This shape shifting can be triggered by external stimuli such as: pH, temperature, humidity, light, presence of specific molecules, among others. In this work, we present important concepts of the properties, synthesis and characterization of hydrogels. Subsequently, the main characteristics of actuators are detailed, and the results of these works are explained with to the previously described properties.