A mould-free soft-lithography approach for rapid, low-cost and bulk fabrication of microfluidic chips using photopolymer sheets

Abstract

Most of the existing microfluidic chip fabrication techniques are very complex, time-consuming, costly, and are not amenable to mass manufacturing. Impending commercialization of lab-on-a-chip devices demand development of new microfabrication methods that involve least procedural complexities using cost-effective materials. This paper proposes an inexpensive and time-efficient procedure for constructing microfluidic devices on a flexographic sheet which is available as commercial-off-the-shelf material, using a mould-free soft-lithography approach. Microchannel design is transferred to a negative-resist photopolymer sheet (PPS) using collimated ultraviolet (UV) rays and etching is performed to remove unexposed material. The microchannel network is sealed on the top by a photopolymer sheet of the same material and pressure-assisted bonding is performed in the presence of UV. The cross-linking between photopolymers in the mating surfaces ensures relatively high bond strength and perfect sealing. Simple and complex microchannel network with 100–500 \(\upmu\)m width is created using this method and various characterization tests are performed. A functional leakage test ensured that the fabricated chip could withstand 200 kPa pressure at a maximum flow rate of 12 mL/min. Cell culture, biomolecule visualization, and droplet mixing dynamics are studied in the microchip to demonstrate its practical utility. Moreover, a large-area chip with 260 \(\times\) 190 mm\(^2\) is created using PPS with this three-step method. Most importantly, this method could mass produce 24 microchips with multiple designs within a span of 2 h. In other words, the average time incurred for the fabrication of a single microchip (50 \(\times\) 30 mm\(^2\)) is less than 5 min. Results suggest that it is a promising method flexible enough to create large-sized chips and to bulk-fabricate microchips having versatile channel designs with high fidelity. Since flexographic infrastructure and materials are very cheap and common in resource-limited settings, the proposed method assumes more importance in the context of rapid commercialization of lab-on-a-chip devices.