Diagnostic of flow disturbances in a cross-shaped micromixer using wall electrochemical probes

The understanding of physical phenomena such as flow behavior is essential in order to develop appropriate micromixers for industrial or biomedical applications. In this paper, the relevance of an electrochemical method is demonstrated for a microfluidic diagnostic in the case of high fluctuating flow, over a wide range of Reynolds numbers (300 < Re < 800) corresponding to the engulfment flow regime. An experimental analysis of the signal measured at microprobes embedded to the wall of microsystems is discussed. The power spectral density (PSD) of the wall shear rate is then obtained by discrete Fourier transform of the signal. Information about the interaction flow structures/walls can be obtained by analyzing the PSD of the wall shear rate. The electrochemical technique is applied to flow within a cross-shaped micromixer with channels having square cross-sections of 400 μm in side. The inlet and outlet channels are symmetric. The PSD of wall shear rate fluctuations reveals various flow characteristics depending on the inlet flow rate and the probe positions along the microchannel. A comparison with results previously obtained with this kind of micromixers allows concluding about the length of flow establishment in such systems.

► Power spectral density of the wall shear rate analysis. ► Information about the interaction flow structures/walls in micromixer. ► Relevance of electrochemical method for a microfluidic in the high fluctuating flow.