(480c) Wetting by Moving Triple Lines

Wetting hysteresis was experimentally studied on smooth, chemically heterogeneous surfaces using a modified Wilhelmy plate apparatus. The novelty in the current set up lies in its ability to capture the microscopic triple line kinetics in addition to measuring the macroscopic contact angle during the advancing and receding processes. The motion of the triple line is known to play an important role in determining the macroscopic contact angle due to its ability to be pinned at various defect locations on real surfaces. This results in contact angle hysteresis.

Chemical heterogeneity was initially introduced by silanization of a part of smooth glass slide (innately hydrophilic) along its length. The triple line was observed to readily wet the hydrophilic material and hesitant to wet the hydrophobic (silanized) material. This study was extended to one and two-dimensional heterogeneities. The work provides insight into the fabrication of chemically heterogeneous surfaces for desired wetting applications.