Reducing the droplet/solid interfacial sliding resistance under electrowetting-on-dielectric by different voltage slew rate signals

Abstract

Reducing droplet/solid interfacial sliding resistance directly by applied voltage is still a scientific challenge. In this paper, the droplet/solid interfacial stick-slip behaviors were studied under different slew rates using an electrowetting-on-dielectric device. Results showed that the slip amplitude and slip times of the triple contact line were significant changed by voltage slew rate signals. The triple contact line slipped at least eight times before saturation at 1 V/s, however, it slipped five and three times at 10 V/s and 50 V/s respectively. The slip amplitude increased by a factor of four when the voltage slew rate increased from 1 V/s to 50 V/s. Dynamics analysis indicated that the large slip amplitude was caused by inertia effect under high voltage slew rate. Moreover, the energy dissipation mechanisms transited from viscous dissipation to molecular friction dissipation with increasing of voltage slew rate. Results revealed that the sliding resistance decreased directedly by applied direct current voltage. Consequently, the droplet/solid interfacial sticky behaviors caused by applied voltage can be decreased without external setups, which is helpful for miniaturizing and integrating of microfluidic setups. Furthermore, the findings extend the understanding of the droplet/solid interfacial stick-slip mechanisms under applied voltage.