Evaporation mediated translation and encapsulation of an aqueous droplet atop a viscoelastic liquid film

JOURNAL OF COLLOID AND INTERFACE SCIENCE

卷:581

Article

Subramanian, Sri Ganesh¹  Nair, Sachin^1,2  DasGupta, Sunando¹ 

[1] Indian Inst Technol Kharagpur, Dept Chem Engn, Kharagpur 721302, W Bengal, India

[2] Univ Twente, Phys Complex Fluids MESA Inst Nanotechnol, NL-7522 NB Enschede, Netherlands

关键词: Viscoelastic liquid;    Self-propulsion;    Evaporation;    Crumpling;    Encapsulation;   

DOI  :  10.1016/j.jcis.2020.07.123

来源: Elsevier

【 摘 要 】

Hypothesis: Viscoelastic liquids could be used as potential substrates in the microfluidics paradigm. The theoretical and experimental investigation of an evaporating aqueous droplet, over a viscoelastic liquid substrate, could provide a fundamental perspective of the complex interplay amongst capillarity, viscosity, and elasticity, resulting in a wide array of intriguing dynamics, which could be important in several microscale processes. Experiments: The evaporation dynamics of a water droplet atop an un-crosslinked polydimethylsiloxane film (polymeric liquid substrate) are examined using an optical goniometer and a laser scanning confocal microscopy, to discern the interfaces. The recorded videos were analyzed to estimate the contact angles, velocities, and other parameters of relevance. Findings: The viscoelasticity of the film, in conjunction with evaporation, triggered a self-propulsion in the droplet, leading to crumpling of the polymeric film, and finally culminating in the encapsulation of the water drop by the polymer. The evaporation caused a dynamic variation in both the radius and contact angle of the droplet. The physics of the hitherto unreported phenomena is explained via the development of a semi-analytical model, considering all the relevant forces. We postulate that this symbiotic and self-sustained dynamics would pave the path towards the comprehension of micro-swimmers and surface encapsulation, to name a few. (C) 2020 Elsevier Inc. All rights reserved.

【 授权许可】

Free