Water slip and friction at a solid surface

A versatile micro- particle imaging velocimetry ( mu- PIV) recording system is described, which allows us to make fluid velocity measurements in a wide range of flow conditions both inside microchannels and at liquid - solid interfaces by using epifluorescence and total internal reflection fluorescence excitation. This set- up has been applied to study the slippage of water over flat surfaces characterized by different degrees of hydrophobicity and the effects that a grooved surface has on the fluid flow inside a microchannel. Preliminary measurements of the slip length of water past various flat surfaces show no significant dependence on the contact angle.