TY - JOUR
T1 - Droplet evaporation on functional surfaces
AU - Alperen Günay, A.
AU - Gnadt, Marisa
AU - Sett, Soumyadip
AU - Oh, Junho
AU - Miljkovic, Nenad
N1 - The authors gratefully acknowledge funding support from the National Science Foundation under Award No. 1554249. N.M. gratefully acknowledges funding support from the International Institute for Carbon Neutral Energy Research (WPI-I2CNER), sponsored by the Japanese Ministry of Education, Culture, Sports, Science and Technology. SEM imaging was carried out at the Beckman Institute for Advanced Science and Technology, University of Illinois.
PY - 2018
Y1 - 2018
N2 - Droplet evaporation is an important phenomenon governing many man-made and natural processes. Characterizing the rate of evaporation with high accuracy has attracted the attention of numerous scientists over the past century. Traditionally, researchers have studied evaporation by observing the change in the droplet size in a fixed time interval. However, the transient nature coupled with the significant mass-transfer governed gas-dynamics occurring at the droplet three-phase contact line make the classical method crude. Furthermore, the intricate balance played by the internal and external flows, evaporation kinetics, thermocapillarity, binary-mixture dynamics, curvature, and moving contact lines make the decoupling of these processes impossible with classical transient methods. Here, we use our recently developed spatially-steady method to characterize the rate of evaporation of sessile droplets on functional surfaces. By utilizing a piezoelectric dispenser to feed microscale droplets ( ≈ 9 µm) to a larger evaporating droplet at a prescribed frequency, we can both create variable-sized droplets on any surface, and study their evaporation rate by modulating the piezoelectric droplet addition frequency. Using the spatially-steady technique, we studied water evaporation of droplets having base radii ranging from 30 µm to 270 µm on surfaces of different functionalities (45 ≤ a,app ≤ 162, where a,app is the apparent advancing contact angle) under different substrate temperature conditions (30℃ ≤ s ≤ 60℃, where s is the functional surface temperature). Our work shows that the rate of evaporation increases linearly for increasing droplet size, and the surface functionality halts its important role at elevated temperatures.
AB - Droplet evaporation is an important phenomenon governing many man-made and natural processes. Characterizing the rate of evaporation with high accuracy has attracted the attention of numerous scientists over the past century. Traditionally, researchers have studied evaporation by observing the change in the droplet size in a fixed time interval. However, the transient nature coupled with the significant mass-transfer governed gas-dynamics occurring at the droplet three-phase contact line make the classical method crude. Furthermore, the intricate balance played by the internal and external flows, evaporation kinetics, thermocapillarity, binary-mixture dynamics, curvature, and moving contact lines make the decoupling of these processes impossible with classical transient methods. Here, we use our recently developed spatially-steady method to characterize the rate of evaporation of sessile droplets on functional surfaces. By utilizing a piezoelectric dispenser to feed microscale droplets ( ≈ 9 µm) to a larger evaporating droplet at a prescribed frequency, we can both create variable-sized droplets on any surface, and study their evaporation rate by modulating the piezoelectric droplet addition frequency. Using the spatially-steady technique, we studied water evaporation of droplets having base radii ranging from 30 µm to 270 µm on surfaces of different functionalities (45 ≤ a,app ≤ 162, where a,app is the apparent advancing contact angle) under different substrate temperature conditions (30℃ ≤ s ≤ 60℃, where s is the functional surface temperature). Our work shows that the rate of evaporation increases linearly for increasing droplet size, and the surface functionality halts its important role at elevated temperatures.
KW - Droplet
KW - Evaporation
KW - Functional surface
KW - Measurement and instrumentation
KW - Nano/micro
KW - Surface temperature
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M3 - Conference article
AN - SCOPUS:85068349510
SN - 2377-424X
VL - 2018-August
SP - 1285
EP - 1291
JO - International Heat Transfer Conference
JF - International Heat Transfer Conference
T2 - 16th International Heat Transfer Conference, IHTC 2018
Y2 - 10 August 2018 through 15 August 2018
ER -