Chicken wire-like graphene coupled with acrylic elastomer is being tested for possible medical uses such as artificial muscles.
|Crumpled graphene (Xuanhe Zhao/Duke)|
When graphene, a pure carbon material, is layered with acrylic elastomer film, it can act like muscle tissues because of its ability to contract and expand when electricity is applied. Varying voltage levels controls the degree of contraction and relaxation, giving actuation strains above 100%.
"Indeed, the crumpling and unfolding of graphene allows large deformation of the artificial muscle" said Xuanhe Zhao, assistant professor in Duke's Pratt School of Engineering.
"New artificial muscles are enabling diverse technologies ranging from robotics and drug delivery to energy harvesting and storage," Zhao said. "In particular, they promise to greatly improve the quality of life for millions of disabled people by providing affordable devices such as lightweight prostheses and full-page Braille displays. The broad impact of new artificial muscles is potentially analogous to the impact of piezoelectric materials on the global society."
The Duke researchers used an acrylic elastomer, sold commercially by 3M (VHB Tape 4905). "The crumpled graphene electrodes are generally applicable to many other dielectric elastomers, such as silicone rubber and polyurethane rubber," Zhao told Plastics Today.
The atoms in graphene are organized in a manner similar to similar to graphite, but in a one-atom thick sheet. Graphene is believed to have a breaking strength more than 100 times above a (hypothetical)steel film of comparable thickness. As recently as five years ago, it was very expensive to produce graphene through exfoliation, but the material is now available at lower prices.
Results of the Duke research were were published online in the journal Nature Materials.
Zhao's work is supported by the National Science Foundation's (NSF) Triangle Materials Research Science and Engineering Center, NSF Materials and Surface Engineering program, and National Institutes of Health (NIH). Other members of the team are Duke's Qiming Wang and Qing Tu.
Researchers at the Massachusetts Institute of Technology reported last summer that because graphene is to thin it changes properties depending on its adjoining material.