A Comprehensive Numerical Analysis of Dielectric-Patterned Hybrid Induced-Charge Electrokinetics for On-Chip Nanoparticle Enrichment

Abstract

Nanoparticle enrichment is critical for analytical chemistry applications in microfluidic chemical and biological analyses, enabling sensitive detection of low-abundance species. Among electrokinetic techniques, induced-charge electroosmosis (ICEO) stands out for its nonlinear electric field response, effectiveness in dilute electrolytes, and independence from solution-specific properties—addressing limitations of conventional methods like centrifugation. Here, we present a dielectric-patterned bottom electrode microfluidic device that generates a hybrid ICEO flow field (a synergy of two modes) for efficient nanoparticle enrichment, designed as a high-performance sample pretreatment module for microfluidic analytical systems. Dielectric patterning induces tangential electric fields—indispensable for ICEO flow—creating alternating conductive grooves and dielectric protrusions. The hybrid field comprises low-frequency, strong converging ICEO flows in grooves (drawing particles to groove centers) and high-frequency, weak quadrupolar ICEO flows around dielectrics (enabling supplementary transport). Via numerical simulations coupling electrokinetic, fluid, and mass transport effects, optimal enrichment (concentration factor >3.6, ∼5 µm narrow band) is achieved at 2 kHz and 3 V, driven by converging flows—this performance directly meets the pretreatment requirements for trace nanoparticle analysis by enhancing sample concentration to detectable levels. Voltage modulation enables dual-target capture: groove centers at low voltages (3–6 V) and dielectric corners at high voltages (12–15 V) via ICEO-dielectrophoresis synergy, expanding the adaptability of the system to diverse analytical detection layouts. The hybrid field exhibits strong frequency/conductivity dependence: Converging flow peak frequencies shift to higher values with increasing conductivity, whereas quadrupolar flows always remain robust in the high frequency limit—supporting the analysis of samples with varying matrix conductivities, a key demand in analytical chemistry. This work advances microfluidic nanoparticle manipulation with a frequency-adaptable platform, overcoming unpatterned electrode limitations (narrow frequency range and poor localization). Potential applications include point-of-care diagnostics, lab-on-a-chip analytical systems, and trace environmental/biological nanoparticle detection, all core focuses of analytical chemistry research.