Bonding-Free Capillary Microfluidics via a 3D-Printed Railed Microchannel

Microfluidics is a promising research area that is widely used in biochemical applications. Recently, the commercialization of microfluidic devices composed of economical plastics has been highlighted. Plastic microfluidic devices must contain conformal contacts to construct a completely closed channel that prevents leakage during liquid transport. However, the conventional fabrication (i.e., injection molding and bonding) of plastic microfluidic devices requires empirical expertise, high cost, time-consuming, and complex procedures. This limits its extensive use in the research and development (R&D) phase to take the next steps toward final commercialization. In particular, iterative changes in the channel design typically lead to increased time and cost. This study proposes an easy-to-change and cost-effective fabrication method for 3D-printed microfluidic devices that offer bonding- and leakage-free spontaneous capillary flow (SCF). Locking pillar arrays on upper and lower substrates are simply and reliably assembled using friction forces. Incorporating inherent fabrication errors in 3D printing allows the intended and reproducible assembly gaps between the substrates to be used as microchannels. In addition, a novel side-opened (side-railed) channel geometry is applied to provide both SCF and virtual sidewalls (i.e., capillary barriers) along the microchannel. Finally, the proposed device demonstrates a potential fabrication method that can be utilized as a bridge between the R&D and commercialization phases.