Magnetic fields and light can be used to assemble, manipulate, and heat nanoparticles (NPs) and to remotely actuate polymer composites. Simple soft robots will be presented, where incorporation of magnetic and plasmonic NPs makes them responsive to magnetic fields and light. Application of magnetic fields to dispersions of magnetic NPs drives their assembly into chains. Dipolar coupling within the chains is a source of magnetic anisotropy, and chains of magnetic NPs embedded in a polymer matrix can be used to program the response of soft robots, while still using simple architectures. Wavelength-selective photothermal triggering of shape recovery in shape memory polymers with embedded Au nanospheres and nanorods can be used to remotely drive sequential processes. Combining magnetic actuation and photothermal heating enables remote configuration, locking, unlocking, and reconfiguration of soft robots, thus increasing their capabilities. Composite and multifunctional NPs are of interest for expanding the properties and applications of NPs. Silica shells are desirable for facilitating functionalization with silanes and enhancing the stability of NPs. Methods for depositing thin silica shells with controlled morphologies onto Au nanorods and CdSe/CdS core/shell quantum dot nanorods will be presented. Silica deposition can also be accompanied by etching and breakage of the core NPs. Assembly of Fe3O4 NPs onto silica-overcoated Au nanorods allows for magnetic manipulation, while retaining the surface plasmon resonance.
Biography: Joseph Tracy is a Professor in the Department of Materials Science and Engineering at North Carolina State University. He completed his undergraduate studies in Chemistry at the University of California, Santa Barbara, in 2000. After receiving his Ph.D. in Physical Chemistry from MIT in 2005, he conducted postdoctoral research at the University of North Carolina, Chapel Hill and joined NC State in 2007. He is a NC State University Faculty Scholar, Humboldt Research Fellow, and recipient of NSF CAREER and Alcoa Foundation Engineering Research Achievement Awards.