Edited by Frank S. Bates, University of Minnesota, Minneapolis, MN, and approved December 18, 2018 (received for review August 31, 2018)
To build new robots that can safely interact with people, while completing complex tasks, we need artificial muscles. Ideally, these devices would be completely soft, as strong as natural muscles, and powered by electricity for easy integration with the rest of the robot. We found a materials solution that relies on an established technology, a dielectric elastomer soft capacitor, which deforms when an electric field is applied. By using a unique combination of nanoscale conductive particles and soft elastomers, we can apply high electric fields and reach contraction forces on par with natural muscles. Potential uses include novel surgical tools, prosthetics and artificial limbs, haptic devices, and more capable soft robots for exploration.
Soft robotics represents a new set of technologies aimed at operating in natural environments and near the human body. To interact with their environment, soft robots require artificial muscles to actuate movement. These artificial muscles need to be as strong, fast, and robust as their natural counterparts. Dielectric elastomer actuators (DEAs) are promising soft transducers, but typically exhibit low output forces and low energy densities when used without rigid supports. Here, we report a soft composite DEA made of strain-stiffening elastomers and carbon nanotube electrodes, which demonstrates a peak energy density of 19.8 J/kg. The result is close to the upper limit for natural muscle (0.4–40 J/kg), making these DEAs the highest-performance electrically driven soft artificial muscles demonstrated to date. To obtain high forces and displacements, we used low-density, ultrathin carbon nanotube electrodes which can sustain applied electric fields upward of 100 V/μm without suffering from dielectric breakdown. Potential applications include prosthetics, surgical robots, and wearable devices, as well as soft robots capable of locomotion and manipulation in natural or human-centric environments.
Author contributions: M.D. designed research; M.D. and E.H. performed research; H.Z. contributed new reagents/analytic tools; M.D. and E.H. analyzed data; and M.D., R.J.W., and D.R.C. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1815053116/-/DCSupplemental.
Published under the PNAS license.
