Microtexture-based passive hydrophobic burst valves in polymeric microfluidics fabricated by femtosecond laser texturing and injection molding

Abstract Hydrophobic burst valves are key elements in lab-on-a-chip devices for point-of-care (POC) testing and biochemical analysis, where passive yet precise fluid control in the microchannels is required. Although numerous fabrication techniques have been developed, many are labor-intensive, involve multiple processing steps, or lack the scalability needed for mass production. To address these challenges, unlike the conventional methods, this work develops microtexture-based passive hydrophobic burst valves in polymeric microfluidic channels through a scalable manufacturing approach that combines femtosecond (fs) laser texturing with injection molding. An inverted microchannel design is first created on a steel mold insert, followed by fs laser texturing of a small channel segment with microcavities at an optimized pitch of 20 µm. Subsequent polymer injection molding replicates the structure in polypropylene (PP), producing a microchannel with integrated micropillars, forming a superhydrophobic barrier governed by Cassie-Baxter wetting state, and functioning as a passive valve. The influence of microchannel height and the number of textured walls on valve bursting pressure is systematically examined. Two channel heights, 50 µm and 140 µm, are investigated, with measurements performed for both single-chip half and double-chip half configurations. The results show that micropillars-induced superhydrophobicity effectively forms a hydrophobic barrier to the fluid flow, with the bursting pressure determined by the contact angle, channel geometry, and the number of textured walls. The valve made in a 50 µm high channel achieves the highest bursting pressure of 1012 ± 59 Pa. To demonstrate the potential of the proposed manufacturing approach, a proof-of-concept microfluidic chip incorporating branched microchannels having distinct bursting pressures is designed and fabricated, enabling precise control over sequential fluid flow. These findings demonstrate that the proposed fabrication strategy not only permits scalable manufacturing of polymer-based microfluidic devices with integrated hydrophobic burst valves but also offers reliable tuning of valve bursting pressures for advanced microfluidic applications.