Public Library of Science, PLoS ONE, 8(7), p. e42848, 2012
DOI: 10.1371/journal.pone.0042848
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This article describes the development and testing of the firstă automatically microfabricated probes to be used in conjunction with theă magic angle coil spinning (MACS) NMR technique. NMR spectroscopy is aă versatile technique for a large range of applications, but itsă intrinsically low sensitivity poses significant difficulties ină analyzing mass- and volume-limited samples. The combination ofă microfabrication technology and MACS addresses several well-known NMRă issues in a concerted manner for the first time: (i) reproducibleă wafer-scale fabrication of the first-in-kind on-chip LC microresonatoră for inductive coupling of the NMR signal and reliable exploitation ofă MACS capabilities; (ii) improving the sensitivity and the spectrală resolution by simultaneous spinning the detection microcoil togetheră with the sample at the ``magic angle'' of 54.74 degrees with respectă to the direction of the magnetic field (magic angle spinning - MAS),ă accompanied by the wireless signal transmission between the microcoilă and the primary circuit of the NMR spectrometer; (iii) given the highă spinning rates (tens of kHz) involved in the MAS methodology, theă microfabricated inserts exhibit a clear kinematic advantage over theiră previously demonstrated counterparts due to the inherent capability toă produce small radius cylindrical geometries, thus tremendously reducingă the mechanical stress and tearing forces on the sample. In order toă demonstrate the versatility of the microfabrication technology, we haveă designed MACS probes for various Larmor frequencies (194, 500 and 700ă MHz) testing several samples such as water, Drosophila pupae, adamantaneă solid and LiCl at different magic angle spinning speeds.