Soft Actuators


We are investigating new type of soft actuators by applying existing actuation principles that work with electrical and fluidic inputs.


Dielectric elastomer fiber actuators


Fiber-shaped dielectric elastomer actuators are expected to be highly versatile, as they can be applied to various types of robots thanks to their simple structure. In this study, we showed that a simpler dielectric elastomer fiber actuator can be constructed by using water inside and outside the actuator as an electrode. We also demonstrated swimming of a jellyfish-like robot by applying the actuator.

Keita Shimizu, Toshiaki Nagai and Jun Shintake, Dielectric elastomer fiber actuators with aqueous electrode, Polymers 13(24), p. 4310, 2021.


Monolithic stacked dielectric elastomer actuators


Stacked dielectric elastomer actuators are a promising technology for soft robotics given their behavior exhibiting muscle-like contraction. The fabrication of stacked dielectric elastomer actuators usually requires alternating stacks of dielectric membranes and electrodes, which is laborious. In this study, we have demonstrated a method to monolithically fabricate stacked DEAs without alternately stacking the dielectrics and electrodes in a simple process by injecting liquid metal into the elastomeric structure. This method can be used to fabricate stacked actuators with 3D free forms, such as a fish-shaped soft robot.

Jun Shintake, Daiki Ichige, Ryo Kanno, Toshiaki Nagai and Keita Shimizu, Monolithic stacked dielectric elastomer actuators, Frontiers in Robotics and AI 8, p. 378, 2021.


Dielectric elastomer actuators (DEAs)


DEAs consist of an elastomer membrane sandwiched between two compliant electrodes (see figure on the right). When a high voltage is applied to the electrodes, the membrane shrinks in the thickness direction and expands in the planar direction due to the electrostatic attractive force generated between the electrodes. This deformation can be used as an electrically-controlled actuation for soft robots and stretchable devices. Robots based on DEAs are shown on this page.


Working principle of dielectric elastomer actuators (DEAs)


Fluidic elastomer actuators (FEAs)


Soft structures inflate in response to the input of fluids such as air and liquid, which can be exploited as an actuation principle. The actuator displayed on the right is made of gelatin, which deforms when pressurized by injecting air. The use of gelatin enables biodegradability, a function being able to return to the soil, in soft actuators. This also makes them edible.


Operation of soft gelatin actuators