Surface engineering for enhanced wicking: The role of laser machining and surface roughness

Wicking is an efficient liquid-handling strategy used in biomedicine, textile engineering, and environmental monitoring. Laser micromachining is a powerful method that induces unidirectional wicking by altering a surface's physical and chemical properties in one step. This research examines how laser machining affects the wicking dynamics of open microchannels. Microchannels were fabricated on a pre-laser-machined hydrophobic square on a silicon substrate, and their wicking performance, i.e., flow rate, water meniscus shape, and durability, was evaluated under various conditions, including different laser parameters, channel orientation, and engraving designs. Depending on its distribution, surface roughness, influenced by laser parameters, is critical in enhancing or hindering wicking. The laser can create two distinct wicking modes on a single platform. Increased roughness slows wicking in horizontally oriented channels, while in vertically oriented channels, it significantly boosts the capillary rate. The durability of wicking also depends on surface roughness properties; microchannels with tightly structured textures maintain durable wicking independent of their capillary flow rate. This study provides insights into how laser machining influences wicking dynamics in microstructures, offering strategies for optimizing microfluidic devices.