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Title: Hysteresis of contact angle of sessile droplets on smooth homogeneous solid substrates via disjoining/conjoining pressure
Authors: Kuchin, I.
Starov, Victor
Keywords: Surfaces
Contact angle hysteresis
Surface forces
Issue Date: 2015
Publisher: © American Chemical Society
Citation: KUCHIN, I. and STAROV, V., 2015. Hysteresis of Contact Angle of Sessile Droplets on Smooth Homogeneous Solid Substrates via Disjoining/Conjoining Pressure. Langmuir, 31 (19), pp. 5345-5352.
Abstract: A theory of contact angle hysteresis of liquid droplets on smooth, homogeneous solid substrates is developed in terms of the shape of the disjoining/conjoining pressure isotherm and quasi-equilibrium phenomena. It is shown that all contact angles, θ, in the range θr < θ < θa, which are different from the unique equilibrium contact angle θ ≠ θe, correspond to the state of slow “microscopic” advancing or receding motion of the liquid if θe < θ < θa or θr < θ < θe, respectively. This “microscopic” motion almost abruptly becomes fast “macroscopic” advancing or receding motion after the contact angle reaches the critical values θa or θr, correspondingly. The values of the static receding, θr, and static advancing, θa, contact angles in cylindrical capillaries were calculated earlier, based on the shape of disjoining/conjoining pressure isotherm. It is shown now that (i) both advancing and receding contact angles of a droplet on a on smooth, homogeneous solid substrate can be calculated based on shape of disjoining/conjoining pressure isotherm, and (ii) both advancing and receding contact angles depend on the drop volume and are not unique characteristics of the liquid–solid system. The latter is different from advancing/receding contact angles in thin capillaries. It is shown also that the receding contact angle is much closer to the equilibrium contact angle than the advancing contact angle. The latter conclusion is unexpected and is in a contradiction with the commonly accepted view that the advancing contact angle can be taken as the first approximation for the equilibrium contact angle. The dependency of hysteresis contact angles on the drop volume has a direct experimental confirmation.
Description: This document is the Accepted Manuscript version of a Published Work that appeared in final form in Langmuir copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://dx.doi.org/10.1021/acs.langmuir.5b01075
Sponsor: This work was supported by CoWet ITN, EU; Engineering and Physical Sciences Research Council, (Grant no.: EP/D077869/1); ESA under grant PASTA; COST MP1106 project; and UK-Russia joint project, the Royal Society, UK.
Version: Accepted for publication
DOI: 10.1021/acs.langmuir.5b01075
URI: https://dspace.lboro.ac.uk/2134/18136
Publisher Link: http://dx.doi.org/10.1021/acs.langmuir.5b01075
ISSN: 0743-7463
Appears in Collections:Published Articles (Chemical Engineering)

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