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

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.