Electrostatic xerography-inspired charge printing for multiphase microfluidic manipulation.

HYPOTHESIS: We hypothesize that programmable interfacial charge distributions can generate reconfigurable electrostatic potential landscapes for charge-mediated droplet actuation. By controlling charge magnitude and polarity, it should be possible to decouple actuation from fixed electrode architectures and achieve three-dimensional interfacial transport and reconfiguration. EXPERIMENTS: An electrostatic xerography-inspired charge printing strategy was implemented to systematically control interfacial charge distributions in silicone oil under non-contact and contact-based charge injection modes. Electric-field distributions were simulated, and droplet charge, transport dynamics, and levitation behavior were quantitatively characterized, while particle and bubble manipulation was demonstrated. FINDINGS: Programmable charge distributions enable versatile three-dimensional manipulation of multiphase objects, including transport, levitation, splitting, and trajectory encoding. Under the investigated conditions, Coulomb interactions provide the dominant contribution to droplet translation, while dielectrophoretic and electrohydrodynamic effects contribute to the overall interfacial dynamics. Stable droplet levitation up to 9 mm and an average transport velocity of 31 mm s-1 at 6.5 kV are achieved. A charge-memory-assisted electrostatic actuation mechanism is observed, whereby pre-patterned interfacial charges guide droplet motion without continuous electrode tracking. These findings establish a charge-programmed electrostatic framework for droplet charge-interface coupling within a broader multiphase manipulation platform and provide insight into charge-regulated interfacial transport.