Direct measurement of the apparent slip length

Abstract

We measure velocity profiles in water flowing through thin microchannels, using particle image velocimetry combined with a nanopositioning system. From the velocity profiles, we determine the slip lengths in two cases: Smooth hydrophilic glass surfaces, and smooth hydrophobic glass surfaces, grafted with a monolayer of silane. The slip length is determined within (+/-100 nm) , i.e., five times more accurately than previous work. In all cases, we find that the slip length is below 100 nm.

Microfluidics: The No-Slip Boundary Condition

“…The conclusions have been confirmed by Molecular Dynamics simulations [135] and are consistent with studies of flow in capillaries with diameters of tens of nanometers [3,91]. In this context, the large number of recent published experiments reporting some form of (apparent) slip with λ ∼ 1 nm−1 µm in the flow of Newtonian liquids is surprising [9,16,17,18,29,30,32,33,38,39,40,67,87,88,68,108,116,125,126,150,162,163,178,192,193,194,195], and has allowed to re-discover a few early [29] Poly(carbonate)+PVP SDS solutions studies reporting some degree of slip [21,34,46,141,160]. In part, this chapter is an attempt to describe and interpret these more recent experimental results.…”

Superhydrophobic drag reduction in laminar flows: a critical review

“…It has advantages over other methods in that it not only detects a slip length in a direct way but also provides detailed spatial information of the slip on SHPo surfaces, where the interfacial boundaries are intrinsically heterogeneous. Micro-PIV is known to measure a slip length with an accuracy of 100 nm at best, as its accuracy is limited by the determination of the wall location and the interaction of particles with the wall (Joseph and Tabeling 2005). While a direct way to measure the slip length, PIV is not a direct way if one wants to obtain the drag of a flow, for which shear force reading is an example of a direct method.…”

Reassessing Fast Water Transport Through Carbon Nanotubes

“…The slip length, which describes the velocity discontinuity between the liquid and the solid, is defined as [10][11][12] …”