The design and fabrication of a low-field NMR probe based on a multilayer planar microcoil

The nuclear magnetic resonance (NMR) probe has great influence on signal transmission and reception in NMR technology applications. In this paper, we present a design, fabrication, and test of an NMR probe comprised of a multilayer planar microcoil with a polydimethylsiloxane (PDMS) microchannel. First, geometric parameters of the probe are determined through theoretical analysis. Second, based on a glass substrate, the multilayer planar microcoil is manufactured using repeated photolithography and electroplating processes. During the fabrication process, the polyimide layer is used to package the coil, and the PDMS interlayer is used to adjust the distance from centerlines between the coil and the sample chamber. Third, the resistance and the quality factor of the coil are found to be 1.2158 Ω and 7.217, respectively, at a Larmor frequency of 28.1 MHz. Finally, the NMR probe is tested in an NMR experiment. The transverse relaxation time T₂ for the solid PDMS is 20.6 ± 0.4 ms, which is in agreement with 21.1 ± 0.2 ms obtained by a Bruker Minispec MQ60. Results show that the design and fabrication of this NMR probe are feasible for time-domain NMR applications.