Dielectrophoresis of ionized gas microbubbles: Dipole reversal due to diffusive double-layer polarization

Gas bubbles generated by electrolysis reactions are shown to exhibit anomalous induced ac dipoles and dielectrophoretic behavior that cannot be described by classical Maxwell–Wagner theory. Normal charging and screening of conducting ionized gas in the gas-phase double layer are shown to render the bubble insulating at low ac field frequencies to affect negative dielectrophoresis. This screening effect couples with dielectric polarization at high frequencies to produce no crossover frequency for small bubbles and two crossover frequencies for bubbles larger than a critical size of 40 μm. A double-layer theory accurately captures the two crossover frequencies and critical bubble size behavior.