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Flow boundary conditions from nano-to micro-scales

Profile image of Senay Tewel-deSenay Tewel-de

2007, Soft Matter

Abstract
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The review focuses on the theoretical understanding of fluid-solid boundary conditions, particularly in the context of slippage at solid-fluid interfaces. It discusses the implications of boundary conditions in microfluidics, including the transition from traditional no-slip conditions to potential slippage facilitated by structured surfaces like superhydrophobic materials. The article elaborates on momentum transfer and proposes a framework for analyzing diffusion across interfaces, emphasizing the need for microscopic justifications similarly applied to bulk properties.

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We consider the flow of a Newtonian fluid in a nano or microchannel with walls that have patterned variations in slip length. We formulate a set of equations to describe the effects on an incompressible Newtonian flow of small variations in slip, and solve these equations for slow flows. We test these equations using molecular dynamics simulations of flow between two walls which have patterned variations in wettability. Good qualitative agreement and a reasonable degree of quantitative agreement is found between the theory and the molecular dynamics simulations. The results of both analyses show that patterned wettability can be used to induce complex variations in flow. Finally we discuss the implications of our results for the design of microfluidic mixers using slip.

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