Capillary kinetics of water in hydrophilic microscope coverslip nanochannels

This study analyzed the capillary filling speed of water in hydrophilic microscope coverslip nanofluidic channels with depths ranging from 40 to 575 nm. Nanofluidic channels were fabricated on a substrate of borosilicate glass (thickness of 160 μm) using the buffered oxide wet etching and glass-glass fusion bonding technique. The capillary filling speed was measured and compared with theoretical values. Comparison of capillary filling speed with theoretical values showed that filling speed inside the coverslip nanochannel was lower than the theoretical speed. A finite-element model was established to analyze the capillary filling speed of water in nanochannels. Finite-element analysis and experimental results show that the conventional theoretical formula for predicting the capillary filling speed is inaccurate without adjustable parameters. Experiments show that the capillary filling speed decreases with a decreasing depth of nanochannels. It need fill 8 mm long, 200 μm wide and 40 nm deep nanochannels around 90 s has been demonstrated.