Geometrical Deposits on Microstructured Surfaces

Veronika Kubyshkina,Khellil Sefiane,Daniel Orejon,Coinneach Mackenzie Dover

doi:10.1007/s42235-020-0071-y

Abstract

Research into evaporating droplets on patterned surfaces has grown exponentially, since the capacity to control droplet morphology has proven to have significant technological utility in emerging areas of fundamental research and industrial applications. Here, we incorporate two interest domains — complex wetting patterns of droplets on structured surfaces and the ubiquitous coffee-ring phenomenon of nanofluids containing dispersed aluminium oxide particles. We lay out the surface design criteria by quantifying the effect of pillar density and shape on the wetting footprint of droplets, yielding complex polygon droplet geometries. Our work is not constrained to pure liquids only, as we delve into the shape selection of particle-laden droplets of different concentrations. We visualise the deposition patterns through microscopy on surfaces exhibiting different features and further establish the ordering of particles on microscale surface asperities. At a high nanofluid concentration, we observe intriguing self-assembly of particles into highly ordered intricate structures. The collective findings of this work have the potential to enhance many industrial technologies, particularly attractive for high performance optical and electrical devices.

Highlights

The physical understanding of microscale droplet dynamics has changed the paradigm of many scientific endeavours, due to the growing number of diverse applications, including inkjet printing, polymer-based LED displays, bio-microarrays, and so forth[1,2,3]
Modifying surface characteristics has a profound effect on droplet behaviour, distinguished between scenarios ranging from complete liquid spreading and wetting on hydrophilic structured surfaces, to the formation of pearl drops in a non-wetting situation on hydrophobic textured surfaces – each state desirable for applications in diverse domains[4,5,6,7,8,9,10]
3.1 Droplet wetting profile We examine the wetting profile of pure liquids and particle-laden suspensions on textured surfaces, exhibiting diverse geometrical parameters

Summary

Introduction

The physical understanding of microscale droplet dynamics has changed the paradigm of many scientific endeavours, due to the growing number of diverse applications, including inkjet printing, polymer-based LED displays, bio-microarrays, and so forth[1,2,3]. The increasing ability to engineer surfaces with bespoke topographical and chemical features has been instrumental in studying the intricacies of the wetting phenomenon, leading to enhanced control over the solid-liquid interactions. By integrating physics at the microscale with engineered surfaces, new methods have emerged for manipulating and controlling the solid-liquid interactions. Anisotropic non-wetting behaviour includes directional droplet transportation and roll-off of droplets from surfaces[18,19,20]. Li et al briefly examined the anisotropic footprints of water droplets, demonstrating the transition of wetting shapes by adjusting topological surface features[21]. Water droplets with 3, 4 and 6-fold symmetry have resulted from the anisotropy effect of the lattice arrangement of surface microstructures and their respective geometrical parameters[22]

Methods

Results

Conclusion