Control of slippage with tunable bubble mattresses

Tailoring the hydrodynamic boundary condition is essential for both applied and fundamental aspects of drag reduction. Hydrodynamic friction on superhydrophobic substrates providing gas–liquid interfaces can potentially be optimized by controlling the interface geometry. Therefore, establishing stab...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2013-05, Vol.110 (21), p.8422-8426
Main Authors: Karatay, Elif, Haase, A. Sander, Visser, Claas Willem, Sun, Chao, Lohse, Detlef, Tsai, Peichun Amy, Lammertink, Rob G. H.
Format: Article
Language:English
Subjects:
Boundary conditions
Bubbles
Curvature
Drag reduction
Flow velocity
Fluid mechanics
Fluids
Friction
Friction factor
Hydrodynamics
Microbubbles
Microfluidic Analytical Techniques - instrumentation
Microfluidic Analytical Techniques - methods
Microfluidic devices
Models, Theoretical
Physical Sciences
Simulation
Substrates
Velocity distribution
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Summary:Tailoring the hydrodynamic boundary condition is essential for both applied and fundamental aspects of drag reduction. Hydrodynamic friction on superhydrophobic substrates providing gas–liquid interfaces can potentially be optimized by controlling the interface geometry. Therefore, establishing stable and optimal interfaces is crucial but rather challenging. Here we present unique superhydrophobic microfluidic devices that allow the presence of stable and controllable microbubbles at the boundary of microchannels. We experimentally and numerically examine the effect of microbubble geometry on the slippage at high resolution. The effective slip length is obtained for a wide range of protrusion angles, θ , of the microbubbles into the flow, using a microparticle image velocimetry technique. Our numerical results reveal a maximum effective slip length, corresponding to a 23% drag reduction at an optimal θ ≈ 10°. In agreement with the simulation results, our measurements correspond to up to 21% drag reduction when θ is in the range of −2° to 12°. The experimental and numerical results reveal a decrease in slip length with increasing protrusion angles when θ ≳ 10°. Such microfluidic devices with tunable slippage are essential for the amplified interfacial transport of fluids and particles.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.1304403110