Multiscale\nInvestigation of Liquid Imbibition on an\nElectrodeposited Rough Surface

Hydrophilic and superhydrophilic surfaces are often used\nin various\napplications, such as biomedical surface modification, heat pipe design,\nlab-on-chip devices, microelectronic structure design, etc. Deposition\nof molecules on surfaces and chemical modification of the surface\nare two of the frequently adopted techniques to fabricate hydrophilic\nsurfaces. However, achieving controlled and precise surface roughness\nis an expensive process, and the multiscale nature of liquid imbibition\non rough surfaces complicates the system’s physics. To address\nthis challenge, we propose an alternative approach for creating controlled\nrough surfaces by electrodeposition of copper ions on copper electrodes,\nexplore the influence of various length scales encountered in roughened\nsurfaces, ranging from micrometers to angstroms, and examine the associated\nphysics. The microscale roughnesses are controlled by adjusting the\ndeposition time. A molecular level investigation is employed to probe\nthe intriguing physics of liquid imbibition on the created rough surface.\nThe molecular analysis of droplet contact line dynamics, including\nthe contact angle and footprint radius, shows qualitative alignment\nwith the real systems. Additionally, this study provides new insights\ninto the flow velocities during imbibition within surface asperities\nat the molecular level. Directional velocities, such as axially downward\nand horizontally outward flows, which are otherwise challenging to\nmeasure experimentally, are also evaluated on a molecular scale. These\nfindings provide a fundamental understanding of the intricate phenomena\nof liquid spreading and imbibition on metallic surfaces with randomly\ndistributed rough textures, deepened by molecular-scale insights.\nThe agreement, on a qualitative scale, between the experiments and\nsimulations is successfully established, providing a fundamental understanding\nof the complex phenomena of water droplet imbibition dynamics on an\nelectrodeposited surface.