Evaporation Dynamics of Sessile and Suspended Almost-Spherical Droplets from a Biphilic Surface

Abstract

Research in the field of the evaporation of liquid droplets placed on surfaces with special wetting properties such as biphilic surfaces is of great importance. This paper presents the results of an experimental study of the heat and mass transfer of a water droplet during its evaporation depending on the direction of the gravitational force. A special technique was developed to create unique substrates, which were used to physically simulate the interaction of liquid droplets with the surface at any angle of inclination to the horizontal. It was found that the suspended and sessile droplets exhibited fundamentally different evaporation dynamics. It was shown that the suspended droplets had a higher temperature and, at the same time, evaporated almost 30% faster.

Heating and Evaporation of Sessile Droplets: Simple and Advanced Models

“…The experimental setup used in our study is the same as described in . In this setup, a droplet was placed in a closed box, which ensured that the conditions around the droplet were uniform.…”

“…An NEC TH7102IR thermal imaging camera with a TH 71–377 macro lens was used at wavelengths λ between 8 and 14 μm. The local thermal images were averaged using the ThermoTracer program. , Note that we could not directly measure the temperature of the contact area between the droplet and surface using the approach described above, as neither the water nor the surface were transparent to infrared radiation.…”

“…This coating was applied using the hot wire chemical vapor deposition (HW CVD) method. Then local removal of the water repellent agent was carried out, allowing us to obtain spatial transition from superhydrophobicity to superhydrophilicity …”

“…Note that all results that refer to droplets with initial volumes of 3.2 and 2.2 μL are original. Some results that refer to droplets with an initial volume 5.2 μL were reproduced from so that they could be compared with those that refer to droplets with initial volumes of 3.2 and 2.2 μL.…”

“…Then local removal of the water repellent agent was carried out, allowing us to obtain spatial transition from superhydrophobicity to superhydrophilicity. 6 Note that all results that refer to droplets with initial volumes of 3.2 and 2.2 μL are original. Some results that refer to droplets with an initial volume 5.2 μL were reproduced from 6 so that they could be compared with those that refer to droplets with initial volumes of 3.2 and 2.2 μL.…”