Physics Colloquium: Measuring Magnetic Nanoparticles

At the National Institute of Standards and Technology (NIST), we create standards and study measurement science with a goal of aiding US industry. This talk will discuss our efforts to improve measurements on magnetic nanoparticles. Magnetic nanoparticles in colloidal liquid form are used for damping in vehicle suspensions, MRI contrast agents, heat transfer materials, and even in art installations. The evaluation of nanoparticles for commercial use depends on accurate measurements of their magnetic properties. However, techniques for measuring magnetization of materials are well-developed only for small solid samples such as bulk crystals and thin films. I will discuss the special issues that arise in magnetic measurements of liquid nanoparticle samples. I will also highlight one particular application for these particles: magnetic nanoparticle hyperthermia (MNH) cancer treatment. MNH is a promising method of cancer therapy in which magnetic nanoparticles are targeted to a tumor, an alternating magnetic field is applied, and the magnetic moments of the nanoparticles switch directions, releasing heat and killing tumor cells. This treatment has proven effective in many mouse models and some small clinical trials on humans, and measurement science can help guide commercialization. Questions include: How to accurately measure the heat output of a magnetic nanoparticle sample, and how to compare the potential effectiveness of different nanoparticle samples.