Fabrication of Spherical Cap-shaped Polystyrene Microlenses via Transient Ouzo Effect

Micro/Nano lens-shaped objects fabricated on solid surfaces have extensive applications. It is of significance and challenging to achieve controlled formation of those microlenses. In this report, we presented a new approach to fabricate polystyrene (PS) microlenses on glass substrates using transient toluene droplets. We find that the addition of water droplets into a well-mixed toluene/ethanol binary solution will cause local and temporary over-saturation of toluene in the formed toluene/ethanol/water ternary solutions. This is referred to as “transient Ouzo effect”. The “transient Ouzo effect” results in the nucleation of toluene droplets on spin coated PS films on glass substrates. The PS films were then dissolved by the nucleated toluene droplets and formed toluene/PS mixture droplets. After the toluene was dissolved back into the ternary solutions, the PS microlenses were obtained on the glass surfaces. The influence of PS film thickness and toluene concentration in the toluene/ethanol binary solutions on the fabricated PS lenses was investigated, followed by the tuning of microlens contact angle through a thermal reshaping method. Moreover, experiments were conducted to verify that the fabricated lenses can achieve enhanced optical imaging with an improved resolution.