One common approach to making artificial muscles uses materials called shape memory alloys, such as a mixture of nickel and titanium. (sciencemag.org)
Sandwiched beneath the display are a number of shape memory alloy wires that contract when the phone notifies the user. (hml.queensu.ca)
The MorePhone's curling capabilities come courtesy of shape memory alloy wires that are sandwiched underneath the flexible display and contract when a call, text or email comes in. (newatlas.com)