Position: PhD Candidate
Current Institution: Iowa State University
Abstract: Design of Low Non-Uniform Field Sensors for Portable Diagnostic Systems
The evolution of wearable technologies and, more importantly, consumer awareness demands advancements in sensing mechanisms, analysis, and diagnostics. Magnetic field-based technologies such as current sensing, switching, navigation, and data recording have also evolved with the demand of lower operational power and long-term stability. However, spatial variations in magnetic fields produced by magnets have traditionally been a deterrent towards magnetic sensor utility in non-localized detection. In this work, the possibility of nuclear magnetic resonance (NMR) signal detection in low, non-uniform magnetic fields is explored. Non-uniform magnetic fields produced by permanent magnets were studied, modeled, and tested with portable pulsed field generation systems to validate NMR measurements for test samples placed in non-uniform fields. In this work, finite element simulations were initially used to estimate the spatial magnetic field in the exterior of a cylindrical ring magnet. A small region of uniform magnetic field, commonly called the saddle point occurs at distances equal to the inner radius of the ring magnet. Test samples may be placed at saddle points that occur at locations where the field is maximal in one direction and minimal in another. The static flux density (B) at the saddle point was used to estimate the NMR voltage signal from hydrogen protons placed at the saddle point. From prior literature, it is known that the estimated NMR voltage is proportional to the square of B and the coil sensitivity, which depends on the pulsed field strength. Therefore, an efficient combination of the two interacting fields is required to detect the highest NMR voltage. Through this work, a systematic analysis and development towards designing portable NMR systems for examining localized targets will be achieved. Incorporating the estimations from the simulation results, NMR measurement results and design considerations for the system will be presented.
Neelam Prabhu Gaunkar is a PhD candidate in the Department of Electrical and Computer Engineering at ISU. She received a master’s degree in electrical engineering from ISU in 2014. She is broadly interested in applied electromagnetism and her research interests include magnetic sensors, high-speed systems, and the phenomena of resonance. She won several prestigious awards. She was awarded an IBM PhD Fellowship (2016-18) for her dissertation research, an ASNT (American Society for Non Destructive Testing) Fellowship (2013-14), ISU’s Zaffarano Award for excellence in research (2018), and ISU Graduate Research (2018) and Teaching (2014) Excellence Awards. Since 2014, she published 13 peer-reviewed articles, four articles in education journals, and numerous conference presentations. She is actively involved in inquiry-based course design for undergraduates and has led labs, undergraduate researchers and design teams.