Flow behavior in surface-modified microchannels with polymer nanosheets

The paper describes water flow behavior in surface-modified microchannels. We prepared straight-type microchannels which had rectangular cross sections with four different combinations of microchannel surface wettability; cleaned glass substrates served as hydrophilic microchannel walls and the microchannel walls coated with polymer Langmuir-Blodgett (LB) films were used as hydrophobic surfaces. The polymer LB films were successfully transferred onto glass substrates by vertical dipping method. The flow rates and the water meniscus shape strongly depended on the microchannel surface wettability. The decrease in flow rate with the increasing number of hydrophobic (polymer LB film) surface was attributed to the higher adhesion energy of hydrophobic surface. The Reynolds number was also characterized to be in the order of 10-1, implying a specific feature of microchannel; laminar flow.