The engineering team developed this new technique by using an elastomer based on a UCLA design that does not require rigid parts. Unlike other elastomer designs, the UCLA model does not need to be pre-stretched on to a frame. Instead, the material begins as a liquid and is quickly cured under UV light, producing thin sheets.
An artificial muscle built from a sandwich of soft, stretchable elastomers and carbon nanotubes electrodes. (Image courtesy of Peter Allen/Harvard SEAS.)
The elastomers are sticky by nature and can adhere to one another or to electrodes. Carbon nanotubes are used for said electrodes instead of carbon grease, as in other designs.
To multiply strength and force, the team utilized a sandwich format with alternating layers of elastomers and nanotubes. This allows for practical levels of strength and force, while offering the added efficiency of each nanotube layer being able to power the elastomer above and below it.
"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," explained Mishu Duduta, project team member. "But really thin elastomers are flimsy and can't produce force. A multilayer elastomer is much more robust and can actually provide significant force."
This approach addresses a challenge that has existed in soft-robotics for some time: soft robots tend to be slow and frequently rely on hydraulics or pneumatics, which are energy-hungry and take up space.
In essence, this development breaks away from this requirement and offers muscle-like movement in an engineered system.
This research was undertaken by an engineering team at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS).
For more on soft robotics, read about soft robots for rehabilitation.