Pulsed Laser Ablation on Polymethylmethacrylate (PMMA) Surfaces for Capillary Driven Flows

Developing a surface modification technique that can be applied to a variety of thermoplastic polymers is of great practical importance. Laser surface treatment is one of effective ways to modify the surface property that can be used for various biomedical applications. In this research, we employed a controllable laser ablation technique on a polymethylmethacrylate (PMMA) surface that can improve the surface wetting property. The ablated hierarchical micro- and nano-structures and surfactant coating of dioctyl sulfosuccinate sodium salt induced controllable capillary driven flows. Morphology and wetting properties of laser ablated PMMA surface have been investigated from the perspective of possible applications in lateral flow assay. We also carried out an experimental investigation on controlling the flow rate and dynamics of capillary driven flow influenced by the ablated surface, channel width, aspect ratio, laser pulse step size, and viscosity of test fluids. While the capillary driven flow was found to follow the modified Lucas-Washburn dynamics, we also observed that the distance of advancing front contact line scaled by the hydraulic radius was inversely proportional to capillary number.