Viscous effects on nanoparticle magnetization harmonics

Dynamic magnetization of nanoparticles is a promising means of functional biosensing. We demonstrate a method for rapid monitoring of relative changes in the viscous environment of superparamagnetic nanoparticles using a ratio of magnetization harmonics. Initial results are capable of detecting changes in viscosity on the order of 0.05 cP. This technique should allow for real-time monitoring of many of the dynamic magnetization applications which have been proposed using AC susceptibility. Further, incorporation of this technique into a harmonic-based imaging system like magnetic particle imaging would allow for in vivo functional imaging capabilities. (C) 2009 Elsevier B. V. All rights reserved.