Jump to main content
Jump to site search

Issue 24, 2019
Previous Article Next Article

Microdroplet self-propulsion during dropwise condensation on lubricant-infused surfaces

Author affiliations

Abstract

Water vapor condensation is common in nature and widely used in industrial applications, including water harvesting, power generation, and desalination. As compared to traditional filmwise condensation, dropwise condensation on lubricant-infused surfaces (LIS) can lead to an order-of-magnitude increase in heat transfer rates. Small droplets (D ≤ 100 μm) account for nearly 85% of the total heat transfer and droplet sweeping plays a crucial role in clearing nucleation sites, allowing for frequent re-nucleation. Here, we focus on the dynamic interplay of microdroplets with the thin lubricant film during water vapor condensation on LIS. Coupling high-speed imaging, optical microscopy, and interferometry, we show that the initially uniform lubricant film re-distributes during condensation. Governed by lubricant height gradients, microdroplets as small as 2 μm in diameter undergo rigorous and gravity-independent self-propulsion, travelling distances multiples of their diameters at velocities up to 1100 μm s−1. Although macroscopically the movement appears to be random, we show that on a microscopic level capillary attraction due to asymmetrical lubricant menisci causes this gravity-independent droplet motion. Based on a lateral force balance analysis, we quantitatively find that the sliding velocity initially increases during movement, but decreases sharply at shorter inter-droplet spacing. The maximum sliding velocity is inversely proportional to the oil viscosity and is strongly dependent of the droplet size, which is in excellent agreement with the experimental observations. This novel and non-traditional droplet movement is expected to significantly enhance the sweeping efficiency during dropwise condensation, leading to higher nucleation and heat transfer rates.

Graphical abstract: Microdroplet self-propulsion during dropwise condensation on lubricant-infused surfaces

Back to tab navigation

Supplementary files

Article information


Submitted
09 Mar 2019
Accepted
07 May 2019
First published
08 May 2019

Soft Matter, 2019,15, 4808-4817
Article type
Paper

Microdroplet self-propulsion during dropwise condensation on lubricant-infused surfaces

J. Sun and P. B. Weisensee, Soft Matter, 2019, 15, 4808
DOI: 10.1039/C9SM00493A

Social activity

Search articles by author

Spotlight

Advertisements