Monolith formation and ring-stain suppression in low-pressure evaporation of poly(ethylene oxide) droplets

Baldwin, KA, Roest, S, Fairhurst, DJ ORCID: 0000-0001-5311-0762, Sefiane, K and Shanahan, M, 2012. Monolith formation and ring-stain suppression in low-pressure evaporation of poly(ethylene oxide) droplets. Journal of Fluid Mechanics, 695, pp. 321-329.

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Abstract

When droplets of dilute suspensions are left to evaporate the final dry residue is typically the familiar coffee-ring stain, with nearly all material deposited at the initial triple line (Deegan et al, Nature, vol. 389, 1997, pp. 827-829). However, aqueous poly(ethylene oxide) (PEO) droplets only form coffee-ring stains for a very narrow range of the experimental parameters molecular weight, concentration and drying rate. Instead, over a wide range of values they form either a flat disk or a very distinctive tall central monolith via a four-stage deposition process which includes a remarkable bootstrap-building step. To predict which deposit will form, we present a quantitative model comparing the effects of advective build-up at the triple line to diffusive flux and use this to calculate a dimensionless number χ. By experimentally varying concentration and flux (using a low-pressure drying chamber), the prediction is tested over nearly two orders of magnitude in both variables and shown to be in good agreement with the boundary between disks and monoliths at χ ≈ 1.6.

Item Type: Journal article
Publication Title: Journal of Fluid Mechanics
Creators: Baldwin, K.A., Roest, S., Fairhurst, D.J., Sefiane, K. and Shanahan, M.
Publisher: Cambridge University Press
Date: 2012
Volume: 695
Identifiers:
NumberType
10.1017/jfm.2012.22DOI
Rights: Copyright © 2011 Cambridge University Press.
Divisions: Schools > School of Science and Technology
Depositing User: EPrints Services
Date Added: 09 Oct 2015 11:06
Last Modified: 09 Jun 2017 13:49
URI: http://irep.ntu.ac.uk/id/eprint/22927

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