Dielectric–viscoelastic synergy governing microfluidic actuation in nematic liquid crystal under moderate fields

This study investigates the dielectric–viscoelastic coupling mechanism governing microflow in a 5CB nematic liquid crystal cell driven by moderate electric fields. Through coupled multiscale simulations based on the Leslie–Ericksen theory and experimental validation, we reveal a counterintuitive nonlinearity in the moderate field regime: increasing the electric field strength enhances the transient flow velocity, yet reduces the net displacement efficiency due to an elastic-energy-driven backflow during the field-off relaxation period. A dielectric–viscoelastic torque competition model is developed to elucidate this phenomenon, identifying the Ericksen number as the key dimensionless parameter governing the transition from viscous-dominated to elastic-energy-dominated dissipation. We further identify an empirical threshold in the Ericksen number, within the present parameter space, beyond which elastic energy conversion leads to significant backflow losses. Based on these mechanistic insights, we propose a thickness-adaptive field compensation strategy to optimize device performance across different cell geometries. Our findings provide a quantitative framework for understanding energy dissipation in liquid crystal electrohydrodynamics and offer practical design guidelines for low-power, high-precision liquid crystal microfluidic devices.