Microwave Spectroscopy for Magnetic Nanowires - Exploring Fundamentals and Designing Devices

University Of Minnesota-Twin Cities, Minneapolis MN

Investigators

Abstract

Bio-labels are used as labels and for sorting of cells and bio-species in the medical community. Commercial labels, like fluorophores, are limited to offering 7 unique addresses. This research proposes to develop a method of creating at least 30 unique labels that can be used to label up to 30 cells or bio species. Most labeling techniques also require observation of individual cells, which can be time consuming for large samples or inaccurate if fast image processing is used. Our approach combines magnetic nanowire technology with radio frequency technology to characterize and detect unique nanowire strand systems. We use radio frequency signals to measure the ferromagnetic resonance properties of the magnetic material. By detecting the zero DC magnetic bias ferromagnetic resonance, we can read out 30 nanowires simultaneously based on the material properties of the nanowires set. This solution will revolutionize diagnostics and multi-cell medical research. Similar to the leap from barcodes to QR codes, these nanowires and nanowire arrays will provide a quantum leap to nano-medicine because large samples (e.g. tissues or whole vials) will be multiplexed so that ratios of labels can be detected simultaneously. Additionally, the research will support workforce development of undergraduate and graduate education and will enrich the team's outreach efforts to the K-12 STEM community by providing experience and exposure to exploring fundamental physics, designing materials science, and building diagnostic tools to design and synthesize solutions to enhance the successful diagnosis of deadly diseases. The research will produce a variety of magnetic nanowire systems that can be used as bio-labels. Radio frequency (RF) signals in combination with traditional magnetic methods will be used to characterize the fabricated batches. Once understood, the radio frequency data will be used to aide in the detecting them as similar and mixed nanowire systems. The nanowire arrays of materials will be based on specific metal systems "single or mixed (Co, Fe, Ni, CoFe, NiFe)" that demonstrate unique ferromagnetic resonance response that will correspond to distinct label addresses. The RF signal will be observed as a sharp null in the signal frequency response corresponding to a specific ferromagnetic material. These studies are essential to determine the specific signature of the RF signal and material system, whereby leading to a unique methods for characterizing magnetic nanowires outside of the manufacturing environment. The proposed research will involve design and synthesis of the nanowires (e.g. 10-200 nm in diameter and 0-100 microns long) as well as characterization of material properties using custom high speed chip diagnostic systems to evaluate single and mixed material systems based on static and dynamic magnetic behavior. Feedback from the nanowire diagnostics will be used to re-design solutions that will allow determination of FMR frequency shifts. One major aim being to create "in-situ or self" DC bias that result from an "effective field" formed by careful design of multilayered ferromagnetic/nonmagnetic nanowire configurations for null frequencies in the 9-40 GHz regime.