Discontinuous pinning effect by a hole row to the gas-liquid interface in a parallel gap

Abstract

Discontinuous contact line pinning phenomenon appears when liquid wets discontinuous sharp features. It provides additional resistance to the gas-liquid interface and sometimes can be used as an effective approach for liquid control, such as avoiding liquid leakage by extraction holes in immersion lithography and other microfluidic devices. The discontinuous pinning effect by a hole row to the gas-liquid interface in a parallel gap was investigated in this study. We designed an experiment to investigate the behavior and the maximum resistance pressure of a hole row blocking the air-water interface in the gap. It was observed that the interface was partially pinned by the hole edges, while the unpinned parts was also stopped by the interface stretching. The pinning effect caused the interface distorted and produced additive Laplace pressure to resist the water pressure. Three failure types of the discontinuous pinning system were found, which were related to not only the hole edge pinning effect, but also the shape and position of the contact line. By analyzing the experimental results, analytical models based on the Laplace equation were built to formulate the pinning effects in the paper. The resistance pressure can be determined dependent on the developed analytical method. The experimental results agreed with the models in the failure types and maximum resistance pressure estimations.