Update: read more about Duke's graphene-based artifical muscles research here
Researchers from Duke University are developing ways to control the crumpling and unfolding of large area graphene. By attaching the graphene to a pre-stretched rubber film. When the film was relaxed, parts of the graphene sheet detached, forming an attached-detached pattern with a feature size of a few nanometers. When the film was stretched again, the adhered spots of graphene pulled on the crumpled areas to unfold the sheet.
So basically stretching and relaxing a rubber film, even manually can crumple and unfold large area graphene sheets. This opens up the possibility of all sorts of applications. One example is a graphene film that can be changed from transparent to opaque (it is transparent when stretched but opaque when crumpled).
The researchers are also looking into layering graphene sheets with different polymer films. This makes soft materials that can contract and expand on demand (by applying electricity) - basically acting like artificial muscles. This can be useful in robotics, drug delivery, energy harvesting, energy storage and more. Even lightweight prostheses and morphing displays. This is not the first research that suggests artificial graphene muscles.