Integrated Fabrication of Glass Microfluidic Devices Using PCD Microgrinding and Calcium-Assisted Bonding

Abstract Soda–lime glass is a suitable substrate for solvent-resistant microfluidic devices due to its optical transparency and chemical inertness; however, its application is limited by the difficulty of machining crack-free microchannels and achieving reliable sealing at low temperatures. This study proposes an integrated fabrication process for soda–lime glass microfluidic chips that combines microdrilling with a sacrificial glass layer, peripheral microgrinding with WEDG-fabricated PCD microtools, and low-temperature calcium-assisted glass–glass bonding. Inlet and outlet ports and open microchannels were fabricated on standard soda–lime glass slides by microdrilling and peripheral PCD microgrinding, and the chips were then sealed by low-temperature calcium-assisted glass–glass bonding. A machining strategy involving an axial depth of cut of 1 μm per pass, repeated to a total channel depth of 50 μm at the flow-focusing junction and 100 μm in the downstream outlet section, followed by a single lateral pass at a feed rate of 10 μm/s, was employed. Although this strategy induced a surface texture characteristic of brittle fracture at the channel bottom, the abrasive action of the tool periphery maintained smooth sidewalls and sharp top edges that were sufficient for leak-free calcium-assisted bonding. Functional performance was evaluated in a flow-focusing configuration using a poly(vinyl alcohol) (PVA) aqueous continuous phase and a poly(ε-caprolactone) (PCL)/dichloromethane (DCM) dispersed phase. The devices exhibited leak-free operation and a stable dripping regime, generating nearly spherical PCL microparticles with a narrow size distribution (mean diameter 66.6 ± 3.1 μm, CV = 4.6%). These results support the hypothesis that sidewall and edge quality, rather than channel-bottom surface finish, is the dominant factor governing leak-free operation and droplet-generation stability. The proposed process chain therefore provides a practical route to solvent-compatible glass microfluidic platforms for droplet-based applications under the tested conditions.