Research

Metrology for Magnetic Materials

Magnetic Particle Synthesis and Characterization.I create and characterize magnetic nano- and micro-particles for a range of applications.

High-Frequency Metrology for Microelectronics. The microelectronics industry is developing miniaturized magnetic components to reduce the size, weight, and power of devices. I develop techniques to characterize these materials at high frequencies.

Magnetic Mapping of Magnetic Nanoparticle Clusters. In collaboration with Professor Gunjan Agarwal's group at The Ohio State University (OSU), I study the magnetic properties of magnetic nanoparticle aggregates. Man-made iron oxide nanoparticles are widely used to label cells and molecules, and many organisms also produce naturally occurring iron oxide nanoparticles, called ferritin, to store and regulate iron in the body. Whether synthetic or natural, these nanoparticles have a magnetization that can be exploited for manipulation or sensing in biological environments. However, nanoparticles often aggregate in complex bio-environments, and the effect of aggregation on their collective magnetic properties is not well understood.

For this project, I develop methods to micropattern nanoparticle aggregates with well-defined structural properties, which can then be correlated with magnetic force microscopy measurements performed by collaborators at OSU. These findings could be used to engineer magnetism-based tools for tracking iron nanoparticles in biological systems and develop quantitative histo-magnetic detection schemes for mapping iron deposits in tissue sections.

Sensors and Contrast Agents

Magnetic Sensors. I develop new types of magnetic sensors that can be wirelessly interrogated to measure properties such as pH and temperature.

Contrast Agents and Sensors for Low-Field Magnetic Resonance Imaging (LF-MRI). I am exploring the properties of magnetic nanoparticles and environmentally-responsive polymers for use as LF-MRI contrast agents and sensors.

RF-Addressable MRI Sensors. In previous work, Dr. Gary Zabow at the National Institute of Standards and Technology (NIST) and collaborators in the  Laboratory of Functional and Molecular Imaging (LFMI) at the National Institutes of Health (NIH)  showed that specially shaped magnetic particles could serve as microfabricated multispectral MRI "color" contrast agents and geometrically encoded magnetic sensors (GEMS). One such geometry is a magnetic particle shaped like a hollow cylinder. 

I developed a new type of GEMS that can be produced cheaply using a soft-lithographic technique called micro-molding (some of these particles are shown at right, next to a grain of salt for scale). The particles have a cylindrical-shell geometry that encodes a unique RF signature, and can be made from a "smart" polymer that changes shape in response to specific environmental conditions, such as pH. This shape change produces a corresponding, quantifiable shift in RF frequency that reports on the local microenvironment—a shift much larger than standard nuclear magnetic resonance (NMR) chemical shifts, producing an unambiguous sensing signal.