A high current density DC magnetohydrodynamic (MHD) micropump

Abstract

This paper describes the working principle of a DC magnetohydrodynamic (MHD) micropump that can be operated at high DC current densities (J) in 75-µm-deep microfluidic channels without introducing gas bubbles into the pumping channel. The main design feature for current generation is a micromachined frit-like structure that connects the pumping channel to side reservoirs, where platinum electrodes are located. Current densities up to 4000 A m⁻² could be obtained without noticeable Joule heating in the system. The pump performance was studied as a function of current density and magnetic field intensity, as well as buffer ionic strength and pH. Bead velocities of up to 1 mm s⁻¹ (0.5 µL min⁻¹) were observed in buffered solutions using a 0.4 T NdFeB permanent magnet, at an applied current density of 4000 A m⁻². This pump is intended for transport of electrolyte solutions having a relatively high ionic strength (0.5–1 M) in a DC magnetic field environment. The application of this pump for the study of biological samples in a miniaturized total analysis system (µTAS) with integrated NMR detection is foreseen. In the 7 T NMR environment, a minimum 16-fold increase in volumetric flow rate for a given applied current density is expected.