Electrowetting on dielectrics on lubricating fluid based slippery surfaces with negligible hysteresis

TL;DR

This paper demonstrates that applying a thin dielectric lubricating fluid layer on surfaces significantly reduces contact angle and electrowetting hysteresis below 2°, enabling smoother and more reliable electrowetting control on both smooth and rough surfaces.

Contribution

The study introduces a novel approach of using dielectric lubricating fluid layers to drastically reduce hysteresis in electrowetting on various surfaces.

Findings

Hysteresis reduced to below 2° on smooth and rough surfaces.

Dielectric lubricating fluid layer does not alter the system's capacitance.

Electrowetting behavior fits the Lippmann-Young equation with the fluid layer.

Abstract

Low voltage electrowetting on dielectrics on substrates with thin layer of lubricating fluid to reduce contact angle hysteresis is reported here. On smooth and homogeneous solid surfaces, it is extremely difficult to reduce contact angle hysteresis (contact angle difference between advancing and receding drop volume cycle) and the electrowetting hysteresis (contact angle difference between advancing and receding voltage cycle) below 10{\deg}. On the other hand, electrowetting hysteresis on rough surfaces can be relatively large (>30{\deg}) therefore they are of no use for most of the fluidic devices. In the present report we demonstrate that using a thin layer of dielectric lubricating fluid on top of the solid dielectric surface results in drastic reduction in contact angle hysteresis as well as electrowetting hysteresis (< 2{\deg}) on smooth as well as rough surfaces. Subsequently fitting the Lippmann-Young electrowetting equation to the experimental electrowetting data reveal that the dielectric lubricating fluid layer is only responsible for smooth movement of the three phase contact line of the liquid drop and does not affect the effective specific capacitance of the system.