title: A simple approach for local contact angle determination on a heterogeneous surface.
abstract: We report a simple approach for measuring the local contact angle of liquids on a heterogeneous surface consisting of intersected hydrophobic and hydrophilic patch arrays, specifically by employing confocal microscopy and the addition of a very low concentration of Rhodamine-B (RB) (2 × 10(-7) mol/L). Interestingly, RB at that concentration was found to be aggregated at the air-liquid and solid (hydrophobic patch only)-liquid interfaces, which helps us to distinguish the liquid and solid interfaces as well as hydrophobic and hydrophilic patches by their corresponding fluorescent intensities. From the measured local contact angles, the line tension can be easily derived and the value is found to be (-2.06-1.53) × 10(-6) J/m.
authors.affiliation: NanoScience and NanoTechnology Program, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
authors.forename: Jinbo
authors.initials: J
authors.lastname: Wu
authors.forename: Mengying
authors.initials: M
authors.lastname: Zhang
authors.forename: Xiang
authors.initials: X
authors.lastname: Wang
authors.forename: Shunbo
authors.initials: S
authors.lastname: Li
authors.forename: Weijia
authors.initials: W
authors.lastname: Wen