Geometry-Influenced Slippage on a Bubble Mattress in Microfluidics

ORAL

Abstract

Hydrodynamic slippage is advantageous for drag reduction and it has been achieved with hydrophobic microstructures. Such substrates can provide soft gas/liquid interfaces with shear-free boundary condition, thereby slippage. The establishment of stable soft-interfaces is crucial for the slippage; however, it has been a challenge. In this study, we design and fabricate hydrophobic microfluidic devices, allowing stable two-phase flow with controllable micro-bubbles at the boundary of the micro-channels. We experimentally and numerically exam the geometric effect of the micro-bubbles on the slippage. The effective slip length is measured for a wide range of protrusion angles, $\theta$, using micro-particle image velocimetry. Our measurements reveal a maximum effective slip length approximately at $\theta$ = 10 degrees. In addition, the experimental results show a decrease in slip length with increasing protrusion angles when $\theta > 10^\circ$. The transverse laminar flow over micro-bubbles has also been numerically studied with finite element methods. The experimental results show a good agreement with the numerical results quantitatively.

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Authors

  • Elif Karatay

    University of Twente, Soft Matter, Fluidics and Interfaces Group

  • Sander Haase

    University of Twente, Soft Matter, Fluidics and Interfaces Group

  • Claas Willem Visser

    Universiteit Twente, University of Twente, Physics of Fluids Group

  • Chao Sun

    University of Twente, Physics of Fluids group, University of Twente, Netherlands, Universiteit Twente, University of Twente, Physics of Fluids Group, University of Twente, Enschede, The Netherlands, Physics of Fluids Group, University of Twente, The Netherlands

  • Detlef Lohse

    University of Twente, Physics of Fluids, University of Twente, Enschede, Physics of Fluids, University of Twente, Physics of Fluids group, University of Twente, Netherlands, Universiteit Twente, University of Twente, Physics of Fluids Group, University of Twente, Enschede, The Netherlands, Physics of Fluids Group, Faculty of Science and Technology, J.M. Burgers Center for Fluid Dynamics, and IMPACT Institute, University of Twente, NL, Physics of Fluids Group, University of Twente, The Netherlands

  • Peichun Amy Tsai

    University of Twente, Soft Matter, Fluidics and Interfaces Group

  • Rob Lammertink

    University of Twente, Soft Matter, Fluidics and Interfaces Group