Fast mixing by lamination

A micro mixer based on multi-stage multi-layer lamination is presented. The micro mixer has been designed as an integrated part of a micromachined chemical analysis system. The fabrication technology is based on wet chemical etching of PYREX-glass and silicon substrates which are subsequently bonded anodically. The micro mixer is designed to work in the flow range 1-10 μl/min with a Reynolds number less than 1 and an undisturbed laminal flow pattern. Comprehensive theoretical studies and computer simulations have been carried out in order to understand the detailed flow behaviour and diffusion in the mixer, and to set up design criteria needed to obtain perfect or near perfect multi-layer lamination. As a result of the study of a generic type of micro mixer and flow simulations, the need of a “separation plate” inside each mixer stage is revealed. The performance of micro machined single stage mixers has been verified by mixing experiments using the fast reaction of phenol-red and an acid. The experimental set-up takes advantage of the transparent PYREX-glass plate offering the possibility to study mixing phenomena by video microscopy