Behavior of a sessile droplet over dielectric infused hydrophobic surface under direct current electric field

Abstract

The manipulation of sessile droplets on hydrophobic surfaces with high controllability, accuracy, and flexibility is vital for various applications of engineering sciences and technology. In this research, the combined effects of a uniform electric field, dielectric infused surface (DIS), and surfactants were investigated for the manipulation and control of sessile droplets on hydrophobic substrates. DIS reduced surface adhesion and enabled the action of electrohydrodynamic and electrophoretic forces. Experimental analysis revealed three different modes of droplet behavior on DIS under varying electro-physical conditions: elongation without motion, elongation with motion, or dispersion. These modes were observed for surfactant concentrations below the critical micelle concentration (CCMC), while elongation leading to restricted spreading of droplet occurred above CCMC. The modes were mapped in the parametric space of electric capillary number (Cae) vs. non-dimensional surfactant concentration (C* = Cs /CCMC), with Cae representing the ratio of interfacial electric to capillary stresses and Cs representing the surfactant concentration. A simple theoretical analysis based on interfacial electric and capillary stress balance distinguished between the stable and unstable configurations. This research contributes to advancing the understanding of droplet manipulation and control, which are critical in emerging microfluidic or biological applications.