Polarization‐Selective Dynamic Coupling: Electrorotation‐Orbital Motion of Twin Colloids in Rotating Fields

This study investigates dynamic electrohydrodynamic (EHD) interactions between two identical colloidal microspheres in rotating electric fields using a fully coupled three-dimensional transient model. Long-range dielectrophoretic (DEP) attraction drives radial convergence; upon near-contact, tangential EHD sliding further induces asynchronous co-field orbital revolution. Crucially, individual electrorotation (ER) not only retains its original direction but also maintains a stable rate-with the rate deviating by <5% from that of isolated particles, matching single-particle behavior. High-frequency DEP force polarity reversal establishes stable noncontact equilibria via short-range repulsion. Spectral analyses reveal collective dynamics (radial mobility, orbital motion) stem from rotating electric field-mediated gap modulation rather than altered particle polarization. This dynamic decoupling-governed by the Kramers-Kronig relationship between real (radial DEP) and imaginary (rotational ER) components of polarizability-enables independent positional and rotational control, opening new avenues for noncontact colloidal manipulation in microfluidic mixers and dynamically reconfigurable active matter systems, where conventional DEP-based approaches are limited by coupled dynamics.