Chapter 13: Nanofluid Droplets Drying on Structured Surfaces and Evaporative Self-assembly

Driven by growing applications involving drop interactions with solids and undergoing phase change, the topic of wetting and evaporation/drying of drops on textured surfaces has been subject to extensive recent research. In this chapter we present the results combining the evaporation of sessile droplets laden with nanoparticles and on textured surfaces. The results demonstrate that the size, shape and spacing of textures dictate the initial shape of both pure and nanoparticle-laden low surface tension fluid drops. Circular, square, rectangular as well octagonal shapes are observed respectively. The drying of nanofluid drops on these textured surfaces has been studied to elucidate the deposition of nanoparticles and how they are affected by the textures and initial shape. Particle deposition following dryout is found to be enhanced near the corners where curvature is greatest. Furthermore, at a high nanofluid concentration we observe self-assembly of particles into highly ordered intricate structures deposited at the centre of the droplet.