Authors: F. Schönfeld, K.S. Drese, S. Hardt, V. Hessel and C. Hofmann
Affilation: Institut für Mikrotechnik Mainz –(IMM), Germany
Pages: 378 - 381
Keywords: split-and-recombine, multilamination, chaotic micro mixing
We present a new type of micro mixer relying on a multi-step split-and-recombine (SAR) approach. Using computational fluid dynamics (CFD), a favourable mixer design is identified which allows for an almost ideal multilamination. The numerical results are corroborated by experimental visualization of multilamination and mixing. Multi-step SAR mixing, although being highly regular and uniform, can be characterized by a positive finite-time Lyapunov exponent, a feature commonly associated with chaotic advection. The corresponding exponential interfacial stretching assures highly efficient mixing. By means of CFD multilamination is investigated. In particular for low Reynolds numbers (Re < 30) the CFD results predict an almost ideal multi-lamination. The correponding mixing quality is computed using a semi-analytical approach relying on the explicit solution of the diffusion equation in a co-moving frame of reference. Experimental results obtained for water/glycerol soltions are found to be in excellent agreement with the numerical data and proof the high mixing efficiency due to the regular multilamination. Eventually, we compare the performance of the SAR mixer to that of micro mixers relying on interdigital multilamination and hydrodynamic focusing and find it to be superior in terms of mixing efficiency, mixing time and pressure drop in the regime of small Reynolds numbers.