Microchannels Constructed on Rough Hydrophobic Surfaces

A microchannel was constructed between two glass slides, taking advantage of their surface properties. The channel geometry was defined by a line that was previously printed on the slide surface using a highly water-soluble liquid [2-(2ethoxyethoxy)ethanol] as the ink. Water, which acted as the working fluid flowed along this line. Although the channel did not have any sidewalls, the water was fixed along the printed line due to the large contact-angle hysteresis of the slide surface whose properties were rough and hydrophobic. Such roughness was more advantageous over smoothness due to the large contact-angle hysteresis of water and the good wettability of the ink. Using a syringe pump, the water was able to continuously flow through a 1 mm wide and 0.13 mm deep channel without flooding.