TY - GEN
T1 - To slip or not to slip - Water flows in hydrophilic and hydrophobic microchannels
AU - Choi, Chang Hwan
AU - Westin, K. Johan A.
AU - Breuer, Kenneth S.
PY - 2002
Y1 - 2002
N2 - The slip effects of water flow in hydrophilic and hydrophobic microchannels of 1 and 2 μm depth are examined experimentally. Fabrication processes for silicon/Pyrex microchannels were chosen to ensure good control of the channel height and to obtain atomically smooth surfaces. Hydrophilic surfaces were prepared with an RCA-1 cleaning, while hydrophobic surfaces were created by coating the channel surface with the self-assembled monolayer of octadecyltrichorosilane (OTS). The flow rates of pure DI water at various applied pressure differences for each surface condition were measured using a high precision flow metering system and it was observed that the flow rates in hydrophobic channels is larger than in the same hydrophilic channel. The increase of the flow rate can be explained by assuming a slip velocity at the wall. The slip effects become more pronounced as the channel height decreases and the wall shear rate increases. The slip length was found to vary as approximately the square root of the shear rate and had values of approximately 40 nm in the hydrophobic channels and 15 nm in the hydrophilic channels at a shear rate of 105 s-1.
AB - The slip effects of water flow in hydrophilic and hydrophobic microchannels of 1 and 2 μm depth are examined experimentally. Fabrication processes for silicon/Pyrex microchannels were chosen to ensure good control of the channel height and to obtain atomically smooth surfaces. Hydrophilic surfaces were prepared with an RCA-1 cleaning, while hydrophobic surfaces were created by coating the channel surface with the self-assembled monolayer of octadecyltrichorosilane (OTS). The flow rates of pure DI water at various applied pressure differences for each surface condition were measured using a high precision flow metering system and it was observed that the flow rates in hydrophobic channels is larger than in the same hydrophilic channel. The increase of the flow rate can be explained by assuming a slip velocity at the wall. The slip effects become more pronounced as the channel height decreases and the wall shear rate increases. The slip length was found to vary as approximately the square root of the shear rate and had values of approximately 40 nm in the hydrophobic channels and 15 nm in the hydrophilic channels at a shear rate of 105 s-1.
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U2 - 10.1115/IMECE2002-33707
DO - 10.1115/IMECE2002-33707
M3 - Conference contribution
AN - SCOPUS:78249268266
SN - 0791836487
SN - 9780791836484
T3 - ASME International Mechanical Engineering Congress and Exposition, Proceedings
SP - 557
EP - 564
BT - Electronic and Photonic Packaging, Electrical Systems Design and Photonics, and Nanotechnology
ER -