The Electr(okinet)ic Slide: Bioinspired Fabrication for Steering Particles in AC Electric Fields by Shape-Morphing and Precise Metal Patches

Active particles are analogs of natural microorganisms, as they locally dissipate energy to propel in low Reynolds number fluids. However, most active particles studied to date possess basic designs that result in a limited diversity of motions. Further, most active particles are compositionally rigid, limiting their ability to adapt to their environment. In this talk, I will share two developments from our lab to better control the precision and dynamics of particle motion in AC electric fields. First, I will describe a fabrication technique combining two-photon lithography and sacrificial stencil masking to deposit precise 2D metal patches onto particles of any shape. Using this method, we created particles with precisely controlled trajectories in 3D. Second, I will describe a class of stimuli-responsive particles that exhibit fully reversible and shape-dependent propulsion. The particles comprise a bilayer of a thermoresponsive hydrogel and a non-swelling glassy polymer. We show that temperature changes drive changes in particle shape and polarizability. These changes enable toggling between linear to helical swimming to enable in situ steering in AC electric fields. In sum, these developments offer a path to better mimic the beauty and dynamics of natural microorganisms.