Application of Microchip Fabricated of Photosensitive Glass for Thermal Lens Microscopy

Conventional wet chemical processes have not been successful in achieving a high aspect ratio channel on glass wafers because of isotropic etching of glass by hydrogen fluoride (HF). We fabricated a microchip of photosensitive glass in order to obtain a high aspect ratio channel (width:depth:aspect ratio = 150 µm:250 µm:1.67). The water glass bonding technique was applied to bond glass wafers at low temperature (40–80°C). The results of studying the characteristics of the water glass bonding technique for the micro total analysis system (µ-TAS) use show that dissolution of the material (sodium) from water glass layer was avoided by placing it in deionized water at 60°C for 4 h, and the bond strength was weakened by keeping it at high pH for a day. The microchip was available to analyze the amount of nitrite acid present by thermal lens microscopy as one method of optical chemical analysis. Although the etched glass surface had a roughness of about 1 µm, the calibration curve of thermal lens microscopy was similar to that of spectrophotometry.