Spatial Control of Activity in Acoustically Energized Active Liquid Crystals

Spatiotemporal modulation of activity in active nematics offers a powerful way to create programmable material responses, ranging from self-pumping flows and reconfigurable textures to autonomous transport. While these phenomena have been widely explored in simulations, experimental realizations have remained limited, mainly due to challenges in maintaining and precisely controlling activity in real systems. In this talk, I will present a new experimental platform based on acoustically energized liquid crystals (AELCs), a quasi-two-dimensional active nematic where we can modulate local activity simply by varying the channel height. This spatial control allows us to generate and steer topological defects in a programmable way. Using microfabricated PDMS channels with sawtooth patterns, we observe persistent defect currents whose direction is dictated by the geometry-defined activity gradient. Finally, a simple phenomenological model confirms that this directed transport originates from spatial activity modulation rather than geometric confinement. Together, these results establish a robust and scalable approach for realizing microfluidic circuits capable of topological manipulation, transport, and even information processing.