Researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have developed a dielectric elastomer with a broad range of motion. The soft material requires relatively low actuation voltage and no rigid components.

An artificial muscle built from a sandwich of soft, stretchable elastomers and carbon nanotube electrodes. This type of actuator could be used in wearable devices, soft grippers, laparoscopic surgical tools, robots, and more.
(Credit: Peter Allen, Harvard SEAS)

“We think this has the potential to be the holy grail of soft robotics,” said Mishu Duduta, a graduate student at SEAS and first author of the paper. “Electricity is easy to store and deliver but until now, the electric fields required to power actuators in soft robots has been too high."

In building a new dielectric elastomer, the team combined two known materials that worked well individually — an elastomer based on one developed at UCLA that eliminated the need for rigid components and an electrode of carbon nanotubes developed in Harvard's Lab.

The modified materials begin as liquids and can be cured rapidly under UV light to produce paper-thin sheets. Because the sheets are sticky, the materials adhere well to each other, and to the electrodes.

For the electrodes, the team replaced carbon grease, typically used as an electrode in dielectric elastomers, with a mat of thin carbon nanotubes. The nanotubes neither increase the stiffness of the elastomer nor decrease the energy density — meaning the elastomer can still stretch and provide significant force.

“The voltage required to actuate dielectric elastomers is directly related to the thickness of the material, so you have to make your dielectric elastomer as thin as possible,” said Duduta. “A multilayer elastomer is much more robust and can actually provide significant force.”

The actuator could be used in a variety of applications, including wearable devices, laparoscopic surgical tools, and artificial muscles.