Microfluidic Platform for Magnetic Nanoparticle Trapping and Detection

Abstract

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 at a flow rate of 5 . 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.

Magnetic particle characterization—magnetophoretic mobility and particle size

“…The Hyperflux Velocimeter (Fig. 1A) includes a channel cell, a magnet assembly providing an isodynamic magnetic field and gradient (13)(14)(15)27), and an automated pump for sample changing, a high-sensitivity and high-resolution (4.4 mm) Grasshopper V R monochrome 2.0 MP Fire-Wire CCD camera (Point Grey, Richmond, BC, Canada) combined with a 23 to 83 telecentric lens (Edmund Optics, Barrington, NJ) to capture darkfield images of the moving particles at 30 frames per second as part of a fully automated process. The 63 telecentric lens used in this study results in a 0.733-mm point-to-point resolution in the object plane within the 400-mm-thick liquid sample cell.…”

“…Methods to determine magnetic properties include the vibrating sample magnetometer , superconducting quantum interference device (SQUID; Refs. and ), and giant magnetic magnetoresistance sensors . These methods provide only bulk average magnetization/susceptibility of a sample.…”