Induced charge electrokinetic manipulation of conductive nanoparticles in polarizable nanofluidic channels

Induced-charge electrokinetics (ICEK) is a versatile tool for micro/nanofluidic manipulation, but its application in nanochannels with structured reservoir-channel interfaces and tunable wall polarizability (dielectric, floating conducting, gate-tunable conducting) remains underexplored, a critical gap for adaptive nanofluidic devices. Here, we present a comprehensive numerical study of ICEK in these three nanochannel types, focusing on conductive nanoparticle arrays in finite Debye length regimes nanoscale induced electrical double layer (iEDL) overlap. We develop a transient multiphysics model (electrostatics-ion transport-fluid dynamics-particle mechanics) with penalty-based contact force and moving iEDL equilibrium analysis. Validated against two classic ICEK benchmarks, the model reliably captures nanoscale ICEK's static/transient nonlinear behaviors. Simulation results: (1) dielectric nanochannels induce quadrupolar induced-charge electroosmotic (ICEO) vortices, creating a central stagnation zone for stable particle trapping and pearl chain formation (PCF); (2) floating conducting nanochannels generate reversed dipolar ICEO flows, realizing symmetric particle ejection into microreservoirs; (3) gate-tunable conducting channels break ICEO symmetry via biasing (negative for rightward, positive for leftward transport), enabling precise reversible directional transport of discrete nanoparticles. Quantitative analysis shows ICEO velocity scales with E2 in dielectric channels, enhanced flow in conducting channels (stronger polarization), and gate-tunable velocity linearly scales with bias. These findings advance nanoscale ICEK understanding (wall polarizability's regulatory role) and establish design principles for adaptive nanofluidic devices (lab-on-a-chip, drug delivery, particle sorting).