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Evaporation-Oscillation Driven Assembly: Microtailoring the Spatial Ordering of Particles in Sessile Droplets

Kabi, Prasenjit and Chattopadhyay, Bidyendu and Bhattacharyya, Soumyadip and Chaudhuri, Swetaprovo and Basu, Saptarshi (2018) Evaporation-Oscillation Driven Assembly: Microtailoring the Spatial Ordering of Particles in Sessile Droplets. In: LANGMUIR, 34 (42). pp. 12642-12652.

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Official URL: http://dx.doi.org/10.1021/acs.langmuir.8b02840

Abstract

This work explores the physical mechanism that can be used to control the final residual pattern of nanoparticles obtained from an evaporating-oscillating sessile droplet. To that end, the substrate is vibrated in the vertical direction with a constant amplitude, while the frequency of excitation is varied. It is found that evaporation progressively shifts the mode number of the oscillating droplet to lower values, while the oscillations enhance the rate of solvent loss, causing a reduction in the droplet lifetime. The coupling between evaporation and oscillation drives the internal flow through two distinct regimes. Initially, oscillation leads to inner flow recirculation, which delays the evaporation driven edge deposition of particles. Subsequently at lower modes, caused by solvent depletion, the effect of oscillation is weakened, which allows evaporation-driven flow to gain prominence and thus transport the dispersed particles to the contact line. We demonstrate here how this delay in particle migration can be controlled to engineer morphological changes in not just the resulting macroscopic aspect of the deposit but also its microstructure. We especially focus on the relatively unexplored microstructural pattern of deposits from evaporating-oscillating droplets. Using scanning electron micrograph and Voronoi tessellation of the final deposit, we show unique spatial variation in particle ordering at macro-micro length scales. Thus, droplet oscillation tunes the spatial extent of the particle ordering crucial in applications like photonic crystals and photonic glass.

Item Type: Journal Article
Additional Information: Copy right for this article belong to AMER CHEMICAL SOC
Department/Centre: Division of Interdisciplinary Research > Interdisciplinary Centre for Energy Research
Division of Mechanical Sciences > Aerospace Engineering(Formerly Aeronautical Engineering)
Division of Mechanical Sciences > Mechanical Engineering
Depositing User: Id for Latest eprints
Date Deposited: 22 Nov 2018 15:04
Last Modified: 22 Nov 2018 15:04
URI: http://eprints.iisc.ac.in/id/eprint/61118

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