Drying of ethanol/water droplets containing silica nanoparticles

Shi, Jing; Yang, Lisong; Bain, Colin D.

Abstract

The evaporation of colloidal drop on a substrate with a pinned contact line usually results in a ring stain (the so-called coffee-ring effect). In this paper, we present an investigation of the evaporation of sessile picoliter droplets of binary solvent mixtures containing fumed silica nanoparticles (NPs). The internal flows in ethanol/water droplets are suppressed and uniform deposit morphology achieved with a low loading (0.2–0.5 vol.%) of hydrophobic fumed silica NPs. The effective control of the particle deposit morphology is based on a rapid sol–gel transition assisted by preferential evaporation of ethanol. For droplets of dilute suspensions, the fumed silica NPs tend to agglomerate and form an elastic network quickly, starting from the region close to the three-phase contact line and below the gas–liquid interface and growing towards the interior of the droplet, as the solvents evaporate and the surface descends. Higher silica particle concentrations, lower ethanol concentrations, and weaker Marangoni flows all contribute to the solgel transition and hence to the suppression of the CRE.

Citation

Shi, J., Yang, L., & Bain, C. D. (2019). Drying of ethanol/water droplets containing silica nanoparticles. ACS Applied Materials and Interfaces, 11(15), 14275-14285. https://doi.org/10.1021/acsami.8b21731

• Journal Article Type: Article
• Acceptance Date: Mar 22, 2019
• Online Publication Date: Mar 22, 2019
• Publication Date: Apr 17, 2019
• Deposit Date: Mar 26, 2019
• Publicly Available Date: Mar 22, 2020
• Journal: ACS Applied Materials and Interfaces
• Print ISSN: 1944-8244
• Electronic ISSN: 1944-8252
• Publisher: American Chemical Society
• Peer Reviewed: Peer Reviewed
• Volume: 11
• Issue: 15
• Pages: 14275-14285
• DOI: https://doi.org/10.1021/acsami.8b21731
• Public URL: https://durham-repository.worktribe.com/output/1305529