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Microuid Nanouid (2012) 12:941951 DOI 10.1007/s10404-011-0928-9
RESEARCH PAPER
Analysis of passive microuidic mixers incorporating 2D and 3D bafe geometries fabricated using an excimer laser
Kevin Conlisk Gerard M. OConnor
Received: 21 August 2011 / Accepted: 29 November 2011 / Published online: 14 January 2012 Springer-Verlag 2012
Abstract We present new passive microuidic mixing structures based on 2D and 3D geometries. The primary mechanism of mixing in these devices is based on chaotic advection. The mixers which incorporate 3D structures introduce transverse ow rotation greatly enhancing performance. Simulations and experimental tests were performed over a Reynolds number (Re) range from 0.1 to 20 and showed good agreement. At an Re of 0.1, 90% mixing was achieved in a path length of 32 and 7 mm, for the 2D and 3D geometrical mixers, respectively. This represents an improvement in performance over a standard T-mixer of 20% for the 2D mixer and 82.5% for the 3D mixer. An inection point in the mixing efciency was observed for both mixer types around an Re of 1. The devices were fabricated on a polymethylmethacrylate (PMMA) substrate, using an excimer laser beam incorporating an intelligent pinhole mask. Initially, structures were developed off-line using a laser simulation tool. A design-of- experiments (DOE) approach along with computational uid dynamic (CFD) analysis was used to optimise mixing element geometry. This precursor to the fabrication step greatly reduces the time between the design stage and device realisation.
Keywords Microuidic mixer Intelligent pinhole
mask Excimer laser PMMA
1 Introduction
Microuidic devices are characterised by low Reynolds numbers (Re), \2,100, which gives rise to laminar ow.
At these low Re values, the turbulence that exists at the macroscale vanishes, and two streams moving side by side in a microchannel mix by diffusion alone (Squires and Quake 2005). This may have some advantages in cell sorting applications (Toner and Irimia 2005), but it is generally seen as a drawback when trying to mix two streams efciently over a short distance. The Reynolds number of a ow is the ratio of inertial forces to viscous forces, and is dened as
Re
qulch
g 1
where q, u, g and lch, represent the uid density, velocity, viscosity and the channel characteristic length, respectively.
Typically, Re is around 1.0 in most...