Aluminium Nanoparticle-Enhanced Optoelectrowetting Device for Effective Light-Driven Droplet Manipulation

Abstract

A new concept of the single-sided continuous optoelectrowetting (SCOEW) device is presented, where light-induced electrowetting performance has been largely enhanced by simply using the layer of aluminum (Al) nanoparticles to achieve effective light-driven droplet manipulations. Previous optoelectrowetting (OEW) studies have used a low-quality photoconductive material made by titanium oxide phthalocyanine (TiOPc) and results in poor OEW modulation. In order to overcome such limitation, we propose the additional layer of Al nanoparticles that enable to improve the conductivity switching capability of the TiOPc layer and thus significantly enhance OEW performance. In this study, both numerical and experimental study results support the working principle of the light-enhanced switching performance for effective OEW modulation. Experimentally, a $2 \mu \mathrm{m}$ thick Al nanoparticle layer at 2 wt% maximizes static contact angle modulation up to 40.7° more than regular cases, and proves a 16-fold increase in droplet actuation speed where a maximum instantaneous speed of 25.64 mm s−1 has been achieved. The nanoparticle-enhanced SCOEW device can be simply fabricated via a spin-coating method as well as allow much improved OEW performance for effective light-driven 3D droplet manipulations, while offering the benefits of device simplicity, flexibility and functionality over conventional EWOD and OEW devices.