Microfluidic Platform for Magnetic Nanoparticle Trapping and Detection

We evaluate giant magnetoresistance sensors to trap and count small concentrations of magnetic nanoparticles (MNPs) within microfluidic flow. The device presented takes the novel approach of capturing and detecting MNPs utilizing the strong fringe-fields present on the periphery of the patterned sensor. The presence of MNPs manifests as a field shift in the magnetoresistance curve. Tests of the device have shown a noticeable response to MNPs with 30 nm nominal core diameters at concentrations as low as $1.2\times 10^{10}\pm 4.0\times 10^{9}\ {\rm MNP/mL}$ at a flow rate of 5 $\mu{\rm L/min}$. Such a device would be beneficial for bio-medical applications, including immunoassays, and for monitoring filtration processes, where large sample fluid volumes and low MNP concentration sensitivities are required.