K
K-9
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Frequency-Tunable Confinement of Active Colloids via Electrohydrodynamic Repulsion
Metallo-dielectric Janus colloids that self-propel under an AC electric field experience a long-range electrohydrodynamic repulsion from patterned obstacles, whose exclusion-zone radius scales inversely with the field frequency (r90 = a/f + c). Students learn how tuning the frequency turns each obstacle into a soft, resizable boundary, opening or closing the gaps between obstacles on demand to gate swimmers into lanes, steer them around bends, and cage them in disordered arrays — a route to sorting and localizing synthetic microswimmers without physically moving the obstacles.