Simple and low-cost production of hybrid 3D-printed microfluidic devices.

The use of three-dimensional (3D) printing for the fabrication of microfluidic chips has attracted considerable attention among researchers. This low-cost fabrication method allows for rapid prototyping and the creation of complex structures; however, these devices lack optical transparency, which greatly hinders the characterization and quantification of experiment results. To address this problem, integrating a transparent substrate with a 3D-printed chip is an effective approach. In this study, we present a solvent bonding method of poly(methyl methacrylate) (PMMA) and acrylonitrile butadiene styrene (ABS) thermoplastic materials for the creation of optically detectable 3D-printed microfluidic devices. To achieve an excellent bonding between PMMA and ABS substrates, we used spray coating as a method for the distribution of ethanol solution followed by UV exposure and post-annealing step to improve the bonding strength. We fabricated a microfluidic chip with S-microchannel to characterize the bonding protocol, and other two application-oriented microfluidic chips, including a 3D split-and-recombine-based passive micromixer, and an integrated microchip for the mixing of two streams of liquid prior to the formation of double-emulsion droplets, to evaluate the efficacy of the proposed scheme. As a result, at least eight bars of the bonding strength between PMMA/ABS substrates was achieved, and the ability of producing optically detectable 3D-printed microfluidic devices based on this bonding method was confirmed.