TY - JOUR
T1 - Onset of Elasto-capillary Bundling of Micropillar Arrays
T2 - A Direct Visualization
AU - Garcia-Gonzalez, Diana
AU - Snoeijer, Jacco
AU - Kappl, Michael
AU - Butt, Hans Jürgen
PY - 2020/10/6
Y1 - 2020/10/6
N2 - When a liquid drop gets into contact with a soft array of microstructures, capillary forces at the three-phase contact line can lead to critical deformations. Microstructures may collapse and form bundles or even patterns. So far, viewing the kinetics of bundling at the menisci scale has remained elusive. Here, we use laser scanning confocal microscopy to directly image the menisci between micropillars. We image structural changes in polydimethylsiloxane micropillar arrays during the Cassie-to-Wenzel transitions of a water drop evaporating on top of the array. We demonstrate how the regular pillar array undergoes a spontaneous symmetry breaking as the first step to the formation of pillar bundles. A comparison of the Cassie-to-Wenzel transition in air and FC40 indicates that the local contact angle determines the outcome of the bundling process. Based on these observations, we develop a simple model using the local contact angle, stiffness of the pillars, and interfacial tension of the liquid to predict the onset of the symmetry breaking.
AB - When a liquid drop gets into contact with a soft array of microstructures, capillary forces at the three-phase contact line can lead to critical deformations. Microstructures may collapse and form bundles or even patterns. So far, viewing the kinetics of bundling at the menisci scale has remained elusive. Here, we use laser scanning confocal microscopy to directly image the menisci between micropillars. We image structural changes in polydimethylsiloxane micropillar arrays during the Cassie-to-Wenzel transitions of a water drop evaporating on top of the array. We demonstrate how the regular pillar array undergoes a spontaneous symmetry breaking as the first step to the formation of pillar bundles. A comparison of the Cassie-to-Wenzel transition in air and FC40 indicates that the local contact angle determines the outcome of the bundling process. Based on these observations, we develop a simple model using the local contact angle, stiffness of the pillars, and interfacial tension of the liquid to predict the onset of the symmetry breaking.
UR - http://www.scopus.com/inward/record.url?scp=85092680976&partnerID=8YFLogxK
U2 - 10.1021/acs.langmuir.0c02147
DO - 10.1021/acs.langmuir.0c02147
M3 - Article
C2 - 32897726
AN - SCOPUS:85092680976
VL - 36
SP - 11581
EP - 11588
JO - Langmuir
JF - Langmuir
SN - 0743-7463
IS - 39
ER -