SYMPOSIA PAPER Published: 01 January 1998

Spreading Mechanisms of “Superwetters” on Hydrophobic Surfaces


Advanced optical techniques, such as differential and common three-phase contact angle interferometry, were developed to monitor simultaneously the meniscus profile, the microscopic three-phase contact angle dynamics, and the wetting film thickness stability during the spreading process of aqueous drops containing polyoxyethylene trisiloxane, 8EO, the so-called “superwetter” (“superspreader”) on solid surfaces. The microscopic observations showed that the superspreading process goes in three stages on hydrophobic solid surfaces. The first stage is driven by the low air/aqueous solution surface tension and the drop will spread first on the solid surface until mechanical equilibrium is reached. In the second stage the drop surface area at the three- phase contact region is stretched and the spreading is driven by the surface tension gradient. The maximum of the lateral velocity of the surface points depends on the local meniscus thickness, viscosity of the fluid at this thickness and the surface tension gradient. Due to the difference in the lateral velocity of the surface points a “bump” is formed at the front of the spreading liquid. In the third stage of the superspreading process the bump breaks into droplet “crowns” and after a while these droplet crowns begin to slide on the solid surface.

Author Information

Nikolov, AD
Illinois Institute of Technology, Chicago, IL
Wasan, DT
Illinois Institute of Technology, Chicago, IL
Koczo, K
Witco Corporation, Organosilicones Group, Tarrytown, NY
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Developed by Committee: E35
Pages: 131–139
DOI: 10.1520/STP14160S
ISBN-EB: 978-0-8031-5392-9
ISBN-13: 978-0-8031-2491-2