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).