Issue Eur. Phys. J. Appl. Phys. Volume 47, Number 3, September 2009 Article Number 31301 Number of page(s) 8 Section Physics and Mechanics of Fluids, Microfluidics DOI 10.1051/epjap/2009108 Published online 12 June 2009

Eur. Phys. J. Appl. Phys. 47, 31301 (2009)
DOI: 10.1051/epjap/2009108

Assessment of mixing in passive microchannels with fractal surface patterning

P.S. Fodor, M. Itomlenskis and M. Kaufman

Physics Department, Cleveland State University, Cleveland, OH 44115, USA

p.fodor@csuohio.edu

Received: 18 February 2009 / Accepted: 17 April 2009 / Published online: 12 June 2009

Abstract
We explore numerically the feasibility of enhancing the mixing capability of microchannels by employing the Weierstrass fractal function to generate a pattern of V-shaped ridges on the channel floor. Motivated by experimental limitations such as the finite resolution (~10 m) associated with rapid prototyping through soft lithography techniques, we study the influence on the quality of mixing of having finite width ridges. The mixing capability of the designs studied is evaluated using an entropic measure and the designs are optimized with respect to: the distances between the ridges and the position range of their tip along the width of the channels. The results are evaluated with respect to the benchmarks established by the very successful staggered herring bone (SHB) design. We find that the use of a non periodic protocol to generate the geometry of the bottom surface of the microchannels can lead to consistently larger entropic mixing indices than in cyclic structures. Furthermore, since the optimization curves (mixing index vs. geometric parameters) are broader at the maximum for fractal microchannels than for their SHB counterparts, the microchannel designs using the Weierstrass fractal function are less sensitive to experimental uncertainties.

PACS
47.85.lk - Mixing enhancement.
47.53.+n - Fractals in fluid dynamics.
47.61.Ne - Micromixing.

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