Combining magnetic forces for contactless manipulation of fluids in microelectrode-microfluidic systems

Hähnel, Veronika GND; Khan, Foysal Z.; Mutschke, Gerd GND; Cierpka, Christian GND; Uhlemann, Margitta GND; Fritsch, Ingrid GND

A novel method to drive and manipulate fluid in a contactless way in a microelectrode-microfluidic system is demonstrated by combining the Lorentz and magnetic field gradient forces. The method is based on the redox-reaction [Fe(CN)6]3−/[Fe(CN)6]4− performed in a magnetic field oriented perpendicular to the ionic current that crosses the gap between two arrays of oppositely polarized microelectrodes, generating a magnetohydrodynamic flow. Additionally, a movable magnetized CoFe micro-strip is placed at different positions beneath the gap. In this region, the magnetic flux density is changed locally and a strong magnetic field gradient is formed. The redox-reaction changes the magnetic susceptibility of the electrolyte near the electrodes, and the resulting magnetic field gradient exerts a force on the fluid, which leads to a deflection of the Lorentz force-driven main flow. Particle Image Velocity measurements and numerical simulations demonstrate that by combining the two magnetic forces, the flow is not only redirected, but also a local change of concentration of paramagnetic species is realized.

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Hähnel, V., Khan, F.Z., Mutschke, G., Cierpka, C., Uhlemann, M., Fritsch, I., 2019. Combining magnetic forces for contactless manipulation of fluids inmicroelectrode-microfluidic systems. Scientific reports, Scientific reports 9, 2019, art,5103. https://doi.org/10.1038/s41598-019-41284-0
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