TY - JOUR

T1 - The final stage of droplet evaporation on black silicon by schlieren technique with a graded filter

AU - Пещенюк, Юлия Александровна

AU - Семенов, Андрей Александрович

AU - Ayvazyan, Gagik Y.

AU - Гатапова, Елизавета Яковлевна

N1 - This study was supported by the Russian Science Foundation (Project No. 20-19-00722).

PY - 2023/1

Y1 - 2023/1

N2 - A reflectance-schlieren technique, enhanced by the stepped gradient filter, is applied for accurate measurements of the map of thin liquid film/droplet thicknesses and surface deformations, allowing measuring angles of surface inclination in the range of [- 5 ∘, 5 ∘]. In the present paper, we investigated the final stage of droplet evaporation of non-volatile water and volatile perfectly wetting liquids FC-72 and HFE-7100. Thin liquid film thickness down to 2 μ m has been measured by using black silicon substrate (b-Si), which has low reflectivity and high absorption of visible light. The substrate is heated in the temperature range from 20 to 50 ∘C. The liquid bump occurrence in the periphery of the non-volatile droplet, the thin liquid film breakup, and ring formation are characterized. The droplet fragmentation into picolitre-sized pieces is observed for volatile low surface tension liquids. The specific evaporation rate is confirmed to increase proportionally to the contact line velocity. The adopted schlieren technique is also found to be applicable for observations from above of the bubble dynamics inside a liquid film and for measurements of the receding contact angles.

AB - A reflectance-schlieren technique, enhanced by the stepped gradient filter, is applied for accurate measurements of the map of thin liquid film/droplet thicknesses and surface deformations, allowing measuring angles of surface inclination in the range of [- 5 ∘, 5 ∘]. In the present paper, we investigated the final stage of droplet evaporation of non-volatile water and volatile perfectly wetting liquids FC-72 and HFE-7100. Thin liquid film thickness down to 2 μ m has been measured by using black silicon substrate (b-Si), which has low reflectivity and high absorption of visible light. The substrate is heated in the temperature range from 20 to 50 ∘C. The liquid bump occurrence in the periphery of the non-volatile droplet, the thin liquid film breakup, and ring formation are characterized. The droplet fragmentation into picolitre-sized pieces is observed for volatile low surface tension liquids. The specific evaporation rate is confirmed to increase proportionally to the contact line velocity. The adopted schlieren technique is also found to be applicable for observations from above of the bubble dynamics inside a liquid film and for measurements of the receding contact angles.

UR - https://www.scopus.com/record/display.uri?eid=2-s2.0-85144300707&origin=inward&txGid=820b91c039ef2dd331a063adb1aa1f6b

U2 - 10.1007/s00348-022-03541-3

DO - 10.1007/s00348-022-03541-3

M3 - Article

VL - 64

JO - Experiments in Fluids

JF - Experiments in Fluids

SN - 0723-4864

IS - 1

M1 - 1

ER -