Bonding of glass-based microfluidic chips at low- or room-temperature in routine laboratory

Abstract

A low- or room-temperature bonding method was developed for fabrication of glass-based microfluidic chips without the requirement of clean environment and programmed high-temperature furnaces. After fundamental pretreatments, the glass substrates and cover plates to be bonded were sequentially soaked in concentrated sulfuric acid, washed with high-flow-rate tap water, de-ionized water and treated using HF steam as a necessary step. Finally, the plates were bonded by bringing the cleaned surfaces into close contact either under a continuous flow of de-ionized water or directly when treated with HF steam, and annealing at low-temperature (<100 °C) or room-temperature. With the key improvements such as fabrication process optimization, gridding channel design and HF steam treatment, the glass-based chips could be obtained with fast, easy and high bonding yields (>90%). The bonding quality of the chips was evaluated by employing SEM, shear strength testing procedure and electric current measurement at different applied voltages. The mechanism for the strong bonding strength was presumably related to the formation of a hydrolyzed layer on the glass plate surfaces after soaking them in acid or water for extended periods. Microfluidic chips bonded by the above method were evaluated in the CE separation of monofuctional reactive dye Cy5-labeled bioamines.