Controlled Movement of Soft Actuators using Multi‐Responsive Microgel Arrays and Microcirculatory Systems

Hydrogels have the potential to provide rapid actuation, high power densities, and versatile power sources to synthetic soft actuators, enabling systems that rival biological actuators. However, slow mass transport of stimuli within hydrogels together with the need for aqueous‐phase operation has limited the performance of devices based on these materials. Here, a free‐standing hydrogel actuator with a purpose‐built microcirculatory system capable of delivering aqueous stimuli for power and control is reported. The device architecture consists of i) micro‐scale hydrogels (microgels) which provide improved mass transport characteristics and ii) an encapsulating membrane with microfluidic channels which enable the controlled delivery of aqueous stimuli and ambient‐phase operation. The microgel actuators exhibit fast response (as low as 30 s) to various stimuli, including temperature, pH, ions, and solvents. The architecture is applied to the design and preparation of devices with micromanipulation and microgripping capabilities. Furthermore, stimuli‐programed actuation is demonstrated through the controlled movements of a multi‐actuator soft robotic “hand”. The design strategies reported provide a new and versatile approach for fabricating, powering, and controlling hydrogel‐based soft actuators and are applicable to soft robotics and stimuli‐responsive sensing systems.