UV Adhesive Hybrid Bonding for Sub-100-μm DLP-3D-Printed Microchannels

We present an effective and practical adhesive bonding method for integrating a 3D-printed microfluidic chip with a polym-ethylmethacrylate (PMMA) substrate. Digital-light-processing (DLP) 3D printing has been extensively used for prototyping microfluidic devices because intricate three-dimensional fluidic structures can be directly printed with high resolution and throughput. However, time-consuming post-processing is typically required for DLP-printed chips due to optical translu-cency, which impedes optical detection and microscopic observation. In addition, monolithic printing of small channels (< 100 μm) has proven particularly challenging due to difficulties in draining uncured resin. To address these problems, we developed an adhesive bonding technique that employs a transparent PMMA cover plate to enclose a DLP-printed open-channel chip, forming a hybrid PMMA-3D print device. This technique leverages vacuum-assisted removal of channel-filling UV adhesive. The resulting bond exhibited excellent burst strength, exceeding 869 kPa (> 8.58 atm), surpassing previously reported values. Furthermore, brightfield and fluorescence imaging revealed that the optical clarity of our hybrid chips was superior to that of chips fabricated entirely using a DLP 3D printer. Channel contamination due to adhesive was minimal, with a reduction in cross-sectional area being less than 6%. Notably, a sub-100-μm microchannel was successfully fabricated without clogging (76.1 × 50.9 μm2 cross-section), significantly smaller than those achieved via monolithic DLP printing or traditional adhesive bonding. As proof of concept, we manufactured hybrid microfluidic devices for inertial focusing and droplet generation, fully functional without leakage. We anticipate that our rapid and effective hybrid bonding method will be widely adopted for the prototyping of microfluidic devices with sub-100-μm features, particularly those requiring optical quantification or microscopic investigation.