The analysis of inductive NMR detection reveals that miniaturisation can potentially help to improve a sensor's signal-to-noise ratio (SNR). Early reports in the 1990's, initiated by Olson et al. in 1995 [1], and based on hand-crafted microcoils, confirmed this prediction, and showed that millimolar sensitivity for nanolitre sample volumes is in principle possible. Building upon these impressive early achievements, my collaborators and I have focused on enabling mass producible miniaturised NMR detectors and systems that show adequate spectroscopic performance. At the intersection of the demands of NMR-compatibility and performance, and requirements imposed by microfabrication methods [2,3], I will show that we have, through extensive simulations and manufacturing process improvements, progressively improved B0- and B1-homogeneity, sample handling, filling factor, detector SNR, and system functionality [4-9]. The cocktail of implementation ideas will cover: Wirebonding and inkjetting as metal micro-structuring methods [2,3], and building upon these processes, an NMR micro-detector with multi-level microfluidic lab-on-a-chip integration [8], a 7-channel micro phased array system [4], signal multiplexing based on a custom 4.3 x 3.4 mm2 CMOS chip [7], a Helmholtz microdetector with disposable sample holder [9], a 100% fill factor microcoil with disposable capillary sample holder [6], and a magic angle coil spinning micro-detector [5]. The application demonstrations will cover:  Spectroscopy of nanolitre volume samples at low concentration, and NMR-microscopic imaging of cells, skin biopsies, and brain slices. Our current work is focusing on the further co-integration of functionality, such as microgradients, or multiple RF channels, and the customisation of the chip laboratory platforms towards the specific needs of various lifescience applications, such as in vivo metabolomics and NMR micro-imaging. As an outlook, I will speculate on where our journey may lead to.

[1] D. L. Olson, et al., High-Resolution Microcoil 1H-NMR for Mass-Limited, Nanoliter-Volume Samples, Science, 270(5244), pp. 1967-1970, 1995.

[2] K. Kratt et al., A fully MEMS-compatible process for 3D high aspect ratio micro coils obtained with an automatic wire bonder, JMM  20(1), p. 015021, 2010.

[3] D. Mager et al., An MRI Receiver Coil Produced by Inkjet Printing Directly on to a Flexible Substrate, IEEE Transactions on Medical Imaging 29(2), pp. 482-487, Feb. 2010.

[4] O. G. Gruschke et al., Lab on a chip phased-array MR multi-platform analysis system, Lab Chip 12(3), pp. 495-502,  2011.

[5] V. Badilita et al., Microfabricated Inserts for Magic Angle Coil Spinning (MACS) Wireless NMR Spectroscopy, PLoS ONE 7(8), p. e42848,  2012.

[6] O. G. Gruschke et al., Water-soluble sacrificial layer enables ultra low-cost LOC integration of magnetic resonance microcoils with 100% filling factor,  17th International Conference on Solid-State Sensors, Actuators and Microsystems (Transducers & Eurosensors XXVII), pp. 132-134, 2013.

[7] M. Jouda et al., CMOS 8-channel frequency division multiplexer for 9.4 T magnetic resonance imaging,   9th Conference on Ph.D. Research in Microelectronics and Electronics (PRIME), pp. 25-28, 2013.

[8] R. C. Meier et al., Microfluidic integration of wirebonded microcoils for on-chip applications in nuclear magnetic resonance, JMM 24(4), p. 045021,  2014.

[9] N. Spengler et al., Micro-fabricated Helmholtz coil featuring disposable microfluidic sample inserts for applications in nuclear magnetic resonance, JMM 24(3), p. 034004,  2014.