Alternating-current induced-charge electrokinetic interactions of two-dimensional cylindrical conductive microparticles near ideally polarizable electrodes: A fully transient numerical investigation incorporating in-liquid multi-body contact

Induced-charge electrokinetics (ICEK), including induced-charge electroosmosis (ICEO) and induced-charge electrophoresis (ICEP), is critical for microfluidic fluid/colloidal manipulation, yet the coupled behaviors of ICEO fluid convection and colloidal ICEP under alternating-current (AC) fields—featuring multiple interfacial charge relaxation mechanisms—remain underexplored. Via full-transient simulations of ideally polarizable two-dimensional (2D) cylindrical conductive particles (radius R = 5 μm) and AC-powered planar electrodes in a rectangular microfluidic chamber, this study finds: single particles stably suspend below fRC−P (particle–electrolyte interfacial double-layer relaxation frequency) via balanced repulsive dielectrophoresis (DEP)/AC-electroosmosis (ACEO) and attractive ICEP, but contact electrodes above fRC−P due to induced electrical double layer short-circuiting; multiple particles show horizontal mutual repulsion, vertical chaotic dispersion (≤fRC−DE, electrode relaxation frequency), near-electrode ordered dispersion (fRC−DE–fRC−P), and stable pearl chains (≫fRC−P); a 4 × 4 array has chaotic dispersion (≤fRC−DE), layered staggered dispersion (fRC−DE–fRC−P), and chained dispersion (≫fRC−P). A novel repulsive DEP between leaky dielectric particles and polarizable electrodes is also identified, confirming AC frequency as a key ICEK regulator and providing a framework for optimizing microfluidic particle sorting/assembly.