Selective laser ablation for in situ fabrication of enclosed channel porous-media microfluidic analytical devices

This work describes a new method for fabrication of enclosed channel porous-media microfluidic analytical devices using selective laser ablation. Microfluidic structures can be readily produced inside the enclosed devices within two fabrication steps. A sheet of porous material was first sandwiched and bonded between two sheets of polymeric film. The porous substrate inside the film layers was then selectively ablated using a laser cutter to create hollow barriers for microfluidic channels. Selective ablation of only the porous layer was achieved because the porous substrate layer is susceptible to ablation by the laser beam, whereas the film layer is resistant to laser ablation due to its light transmission properties. This selective laser ablation processing is not limited by laser type. As a proof-of-concept, two different laser systems, a 10.6 mu m CO2 laser and a 455 nm diode laser, were employed for this purpose. A variety of porous materials, including cellulose, nitrocellulose, and glass microfiber, were combined with a wide variety of polymeric films to fabricate enclosed microfluidic devices. The developed method is versatile; depending on material combination and number of layers of materials in the devices, enclosed microfluidic devices with 2D, passive 3D, or compression-activated 3D fluid flow can be created. Quantitative assays for albumin, glucose, and cholesterol in human serum performed using devices produced via this method demonstrated the utility of this fabrication approach. This unique, simple, and scalable method for fabrication of enclosed microfluidic devices not only ensures protection of devices from contamination and prevention of fluid evaporation, but also offers a method for commercial fabrication of porous-media analytical devices.

Automated summary

This work presents a novel method for fabricating enclosed channel porous-media microfluidic analytical devices using selective laser ablation. By sandwiching a porous material between polymeric films and selectively ablating the porous substrate, microfluidic structures can be easily created within the devices. The method is versatile and can be applied to a wide range of porous materials and polymeric films, resulting in enclosed microfluidic devices with different fluid flow characteristics. The fabricated devices demonstrated their utility in quantitative assays for albumin, glucose, and cholesterol in human serum. This unique and scalable method not only provides protection against contamination and fluid evaporation, but also offers a commercial fabrication approach for porous-media analytical devices.