  Future active metamaterials for reconfigurable structural applications
require fast, untethered, reversible, and reprogrammable (multimodal)
transformability with shape locking. Herein, we aim to construct and
demonstrate a magneto-thermomechanical tool that enables a single material
system to transform with untethered, reversible, low-powered reprogrammable
deformations and shape locking via the application of
magneto-thermomechanically triggered prestress on a shape memory polymer and
structural instability with asymmetric magnetic torque. We demonstrate the
mutual assistance of two physics concepts - magnetic control combined with the
thermomechanical behavior of shape memory polymers, without requiring new
materials synthesis and high-power energy for reprogramming. Our approach can
open a new path of active metamaterials, flexible yet stiff soft robots, and
multimodal morphing structures, where we can design them in reversible and
reprogrammable ways.
