Magnetoresponsive Devices with Programmable Behavior Using a Customized Commercial Stereolithographic 3D Printer

The revolution of 4D printing allows combining smart materials to additive processes to create behavioral objects able to respond to external stimuli, such as temperature, light, electrical, or magnetic fields. Here, a modified commercial digital light processing (DLP) 3D printer is used to obtain complex macroscopic remotely controlled gear-based devices. The fabrication process is based on the printing of magnetoresponsive polymers containing in situ self-assembled microstructures, i.e., composed of oriented chains of Fe₃O₄ nanoparticles (NPs). First, it is demonstrated that magnetoresponsive hammer-like actuators with different stiffness can be printed allowing both pure rotation or/and bending motions. Then, the microstructure to create a magnetoresponsive gear is exploited. In particular, this work shows that they can be successfully used to transfer torque to other gears, thereby converting a rotation movement into linear translation. Finally, it is demonstrated that magnetoresponsive gears can also be combined with other nonmagnetic elements to create complex assemblies, such as gear-trains, linear actuators, and grippers that can be remotely controlled.