Characterizing Magnetic Nanoparticles Using Indicator Films, Fluidic Devices, and Optical Microscopy

Magnetic nanoparticles are becoming increasingly useful for applications ranging from disease diagnosis and therapy to nanoscale robotics. However, even as the number of applications for these particles has increased, the techniques for characterizing them have generally remained as either specialized measurements which cannot be applied routinely, or as ensemble measurements which cannot resolve the properties of single particles determining their collective behavior. In this presentation, I will discuss two measurement techniques that we have recently developed to close this gap, in particular for ferromagnetic nanoparticles. The first is based upon observing the influence of magnetic nanoparticles on an ultrathin magneto-optical indicator film, which amplifies nanoscale magnetic fringe fields into microscale signals for easy, fast measurement. The second technique is based on measuring the motion of magnetic nanoparticles at a microfabricated solid-fluid interface under applied magnetic fields. In this implementation of analytical magnetophoresis, the nanoparticle functions as its own, extremely sensitive, measurement transducer. I will discuss the advantages of these two measurement techniques, and what future insights might be gained from them.