Radio Frequency Planar Coil-Based On-Chip Probe for Portable Nuclear Magnetic Resonance

Miniaturization of nuclear magnetic resonance (NMR) systems has seen a tremendous development during the last two decades. However, it has not gained popularity particularly, for biological investigations due to high manufacturing cost, sophisticated tools requirement, and mismatching problems arising due to connecting wire between radio frequency (RF) coil and transmission line. The aim of the research work presented in this paper is to develop cost effective, portable, and benchtop NMR system for biological investigation related to healthcare. In this paper, RF planar spiral coil is developed on double sided printed circuit board (PCB) using conventional PCB technology having high-quality factor of 29.265 at 21.287 MHz. Then, the same coil is used to develop on-chip NMR probe by extending the transmission line. This developed probe is a novel design, which improves the coupling between RF coil and transmission line; and hence, improves the sensitivity of NMR. A pair of permanent magnets having 0.5 T magnetic field strength with rectangular iron yoke has been used in the NMR system. Finally, the efficiency of this portable NMR was tested by recording the NMR spectrum of human blood cells. The spectrum obtained was compared to the commercial NMR (Bruker, ULTRASHIELD -500 PLUS) and found to be similar with remarkably small sample volume requirement. Moreover, in this research, we report a very low-cost coil and probe with novel probe design using CST tool, for the first time to the best of our knowledge.