# Electrowetting of a nano-suspension on a soft solid

## TL;DR

This paper investigates how adding nanoparticles to a droplet can restore electro-spreading on soft surfaces by altering the interfacial dielectric properties, with a theoretical model explaining the observed phenomena.

## Contribution

It introduces a novel mechanism where nano-particles enhance electro-spreading on soft solids by changing the dielectric constant, supported by experimental and theoretical analysis.

## Key findings

- Nanoparticles recover electro-spreading on soft surfaces.
- The mechanism is limited by particle volume fraction due to contact line pinning.
- A theoretical model explains the experimental results.

## Abstract

The wetting of solid surfaces can be manoeuvred by altering the energy balance at the interfacial region. While electric field acts favourably to spread a droplet on a rigid surface, this tendency may be significantly suppressed over soft surfaces, considering a part of the interfacial energy being utilized to deform the solid elastically by capillary forces. Here, we bring out a unique mechanism by virtue of which addition of nano-particles to the droplet brings in a favourable recovery of the electro-spreading characteristics of a soft surface, by realizing an alteration in the effective dielectric constant of the interfacial region. Our experiments further demonstrate that this mechanism ceases to be operative beyond a threshold volume fraction of the particle suspension, due to inevitable contact line pinning. We also develop a theory to explain our experimental observations. Our findings provide a non-contact mechanism for meniscus spreading and droplet control, bearing far-reaching implications in biology and engineering.

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Source: https://tomesphere.com/paper/1812.10392