Magnetically and Optically Active Nanoparticles and Polymer Composites

Magnetic fields and light are appealing for assembling, manipulating, and heating magnetic microparticles and plasmonic nanoparticles (NPs). Simple soft actuators will be presented, where embedded magnetic microparticles and plasmonic NPs render them responsive to magnetic fields and light. Photothermal triggering of Au nanorods (GNRs) in shape memory polymers and 3D-printed, thermoresponsive hydrogels drives shape morphing. Combining magnetic actuation and photothermal heating enables remote configuration, locking, unlocking, and reconfiguration of soft actuators. Use of hard-magnetic NdFeB microparticles makes possible controlled remagnetization to reprogram soft actuators for new tasks. Composite and multifunctional NPs are of interest for coupled properties that enhance their capabilities. For example, cationic Fe3O4 NPs undergo electrostatic self-assembly on the surface of anionic GNRs, yielding MagGNRs, which align in magnetic fields and have polarization-dependent extinction. Furthermore, pH is a useful lever for controlling the assembly and disassembly of MagGNRs. These materials are promising for applications in soft and nano- robotics, medical devices, imaging, and sensing.