2, Elon University, Elon, North Carolina, United States
Magnetic iron microparticles were embedded in shape memory polymer films through solvent casting. These composites exhibit bifunctional responses because they can be actuated by both magnetic fields and light, which triggers photothermal heating and softens the polymer, thus modulating its magnetic responsiveness. Temporary shapes obtained through combined magnetic actuation and photothermal heating can be locked after switching off the light and magnetic field. When the light is subsequently turned on without the magnetic field, the device returns to its permanent shape. This concept enables the design of materials that are reconfigurable rather than merely responsive. In cantilevers, multiple locking and unlocking cycles are demonstrated. In a flower with magnetic petals, pulsing the light can be used to select which petals are lifted. Scrolls demonstrate that the permanent shape of the film can also be changed, and the scroll can be frozen in open, closed, and intermediate configurations. A bistable snapper can similarly be magnetically actuated and optically locked and unlocked. Reconfigurable grabbers can pick up and release the objects in a repeatable fashion by combining magnets to reset the grabber and light to drive release of an object. Inexpensive permanent magnets and light emitting diodes were used for actuation. Models that account for the magnetic and elastic energies can predict the observed experimental behaviors of these devices. The concept of combining shape memory, magnetic actuation, and photothermal heating significantly enhances the capabilities of magnetic actuators for soft robotics.