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Engineers create portable device for nuclear magnetic resonance spectrometry

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A team of scientists has recently reported the development of a portable device for nuclear magnetic resonance (NMR) spectroscopy, opening up the possibility for on-demand application, or even use where large state-of-the-art systems are not cost efficient.

Led by Donhee Ham, Professor of Electrical Engineering and Applied Physics at Harvard University (MA, USA), the team has managed to significantly reduce the size of the spectrometer components, fitting them onto a silicon chip smaller than a sesame seed. When combined with a compact permanent magnet, the design represents the smallest device that can perform multidimensional NMR spectroscopy.

Commenting on the work, Ham said: “State-of-the-art NMR systems use very large superconducting magnets, and they are indeed necessary for probing the structure of complex molecules like proteins. But in many circumstances – for example, many experiments in biochemistry or organic chemistry, quality control in production lines, or chemical reaction monitoring – you’re doing NMR on smaller molecules, and for those applications the big superconducting magnets may be avoided.”

The authors note that permanent magnets are both weaker and less stable than semiconducting magnets, which presents challenges when miniaturizing the system, as slight changes in temperature can cause fluctuation of the magnetic field.

However, as Ham explains, Dongwan Ha, the principal architect of the silicon chip, found a way to overcome such a problem: “Not only did Dongwan design the chip, but he also came up with a way to use statistical distance minimization and entropy minimization to estimate the magnetic field drift and calibrate out its effect. This signal-processing method obviates the need for physical thermal regulation for the permanent magnet, which would have added hardware and increased the power consumption. That would have defeated our aim of achieving portability.”

The team is now investigating the possibility of conducting several NMR experiments at once to accelerate the analysis of complex molecules. They have also filed for a provisional patent and, together with Harvard’s Office of Technology Development, are exploring avenues for commercialization.

Sources: Ha D, Paulsen J, Sun N, Song YQ, Ham D. Scalable NMR spectroscopy with semiconductor chips. PNAS DOI:10.1073/pnas.1402015111 (2014) (Epub ahead of print); Miniscule chips for NMR spectroscopy promise portability, parallelization.

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