Abstract
Glass microfluidic devices are prominent in the chemical, biological, and pharmaceutical fields because of their good chemical compatibility, structural rigidity, surface modifiability, and optical transparency. Numerous techniques for fabricating glass microchannels in a two-dimensional plane, including nanochannels, have been developed. For the further development of functional and highly integrated microfluidic/nanofluidic devices, the fabrication of three-dimensional channels, including vertical channel structures, is essential. However, vertical channel fabrication is still difficult and faces limitations with respect to the cross-sectional shape of the channel and the channel diameter that can be achieved when conventional fabrication methods are used. To overcome these limitations, we here demonstrate a fabrication method for a 20 µ m-thick glass membrane with penetrating vertical channels. To fabricate the 20 µ m-thick glass membrane, the detachable glass bonding method was used to support the substrate during CNC milling. Under bonding-energy conditions of 0.18 J m −2 in this study, a glass membrane with a diameter of 600 µ m and a thickness of 20 µ m was successfully fabricated. On the fabricated membrane, penetrating vertical channels with diameters of 20 µ m, 40 µ m, 60 µ m, and 100 µ m were successfully produced by photolithography and dry etching. In addition, the cross-sectional shape of the penetrating vertical channels was confirmed to be straight. Finally, the smooth introduction of liquid was demonstrated using the bonded microfluidic device. This study provides a new fabrication method for penetrating vertical channels with a 10 µ m-scale diameter and straight cross-sectional shape and is expected to contribute to the future development of functional glass microfluidic devices with three-dimensional structures.