Abstract
We present a rapid and highly reliable glass (fused silica) microfluidic device fabrication process using various laser processes, including maskless microchannel formation and packaging. Femtosecond laser assisted selective etching was adopted to pattern microfluidic channels on a glass substrate and direct welding was applied for local melting of the glass interface in the vicinity of the microchannels. To pattern channels, a pulse energy of 10 μJ was used with a scanning speed of 100 mm/s at a pulse repetition rate of 500 kHz. After 20–30 min of etching in hydrofluoric acid (HF), the glass was welded with a pulse energy of 2.7 μJ and a speed of 20 mm/s. The developed process was as simple as drawing, but powerful enough to reduce the entire production time to an hour. To investigate the welding strength of the fabricated glass device, we increased the hydraulic pressure inside the microchannel of the glass device integrated into a custom-built pressure measurement system and monitored the internal pressure. The glass device showed extremely reliable bonding by enduring internal pressure up to at least 1.4 MPa without any leakage or breakage. The measured pressure is 3.5-fold higher than the maximum internal pressure of the conventional polydimethylsiloxane (PDMS)–glass or PDMS–PDMS bonding. The demonstrated laser process can be applied to produce a new class of glass devices with reliability in a high pressure environment, which cannot be achieved by PDMS devices or ultraviolet (UV) glued glass devices.
Highlights
Microfluidic devices have been actively researched because they are able to provide rapid reaction and high-throughput screening of very small samples such as protein, DNA, cells, and tissues [1]
To demonstrate our proposed rapid glass microfluidic device fabrication, we chose a droplet generator with a cross junction, because it is widely used in many fields for generating highly reproducible micro- or nano-droplets of water, oil, and other materials [33]
A simple microfluidic channel was patterned on a fused silica glass substrate and successfully bonded with another fused silica glass substrate
Summary
Microfluidic devices (or lab-on-a-chip) have been actively researched because they are able to provide rapid reaction and high-throughput screening of very small samples such as protein, DNA, cells, and tissues [1]. Conventional transparent laser welding is not direct bonding of glass substrates or a single step process. Glass microfluidic device fabrication using a femtosecond laser has been actively researched It has advantages in terms of fabrication compared with the conventional processing methods, including MEMS and photolithography. WWee pprrooppoossee aa rraappiidd aanndd hhiigghhllyy rreelliiaabbllee ffaabbrriiccaattiioonn mmeetthhoodd ffoorr ggllaassss mmiiccrrooflfluuiiddiicc ddeevviicceess tthhaatt ccoonnssiissttss ooff tthhrreeee sstteeppss,, aass sshhoowwnn iinn FFiigguurree 11. When we used a small amount of glue to prevent the blockage, the bonding strength was weak and the two glass substrates came apart Another glass microfluidic device was fabricated with a glue guide trench around the microfluidic channel (Figure 4D). After fabricating the glass microfluidic devices bonded using the UV curable glue, their bonding strength was tested with an internal pressure measurement system
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