A new method for precise optical measurements of the sub-micron height of levitation of droplet clusters--颗粒学报PARTICUOLOGY

Fedorets, A. A., Kolmakov, E. E., & Dombrovsky, L. A. (2024). A new method for precise optical measurements of the sub-micron height of levitation of droplet clusters. Particuology, 87, 173-178. https://doi.org/10.1016/j.partic.2023.08.005

A new method for precise optical measurements of the sub-micron height of levitation of droplet clusters

Alexander A. Fedorets ^a, Eduard E. Kolmakov ^a, Leonid A. Dombrovsky ^{a b c *}

a University of Tyumen, 6 Volodarskogo St, Tyumen, 625003, Russia
b Engineering Faculty, Ariel University, P.O.B. 3, 407000, Ariel, Israel
c Joint Institute for High Temperatures, 17A Krasnokazarmennaya St, Moscow, 111116, Russia

10.1016/j.partic.2023.08.005

Volume 87, April 2024, Pages 173-178

Received 2 June 2023, Revised 27 July 2023, Accepted 13 August 2023, Available online 26 August 2023, Version of Record 8 September 2023.

E-mail: ldombr@yandex.ru; ldombr4887@gmail.com

Highlights

• A new method for precise optical measurements is suggested.

• Sub-micron levitation height of droplet clusters is determined.

• Measured downward velocity of growing droplets is less than 10 nm/s.

• Similar analysis can be used to validate theoretical models for droplet levitation.

Abstract

Droplet clusters levitating over the locally heated water surface are considered a very promising phenomenon of microfluidics for the potential use of the droplets as unique microreactors for microbiological experiments. A new optical method is suggested for precise measurements of the sub-micron levitation height of single droplets. The method is based on the analysis of variable colors of the interference halo around the droplet. For the first time, it is possible to measure the extremely low downward velocity of droplets, which grow due to steam condensation. This velocity was found to be 5–8 nm/s. The height of the levitation of various droplets just before their coalescence with a layer of water was also determined. Such measurements might be used for the verification of sophisticated models for the droplet levitation to be developed for a very thin layer of humid air under the droplet when the Knudsen effect should be taken into account.

Graphical abstract

Keywords

Precise measurements; Interferometric method; Droplet cluster; Levitation height

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