NMR for Process Control. Imaging and Localized NMR in Soft Matter

NMR or nuclear magnetic resonance is a spectroscopic method which employs magnetic fields and radio-frequency waves. In chemistry it is a standard method for structural analysis, but it is also known in medicine as magnetic resonance tomography which is a well-established diagnostic imaging method. Its success in medical imaging derives from the comparatively high sensitivity of protons and the manifold of contrast mechanisms which can be exploited to visualize structures in heterogeneous objects and cannot be resolved by many other methods. The same possibilities exist in materials science comprising product and process control in particular of soft materials like elastomers, polymer melts, and food. While NMR for analysis of chemical structures requires highly homogeneous magnetic fields and thus expensive technology, many issues in materials science and process control can be tackled by NMR in such inhomogeneous fields as generated by simple permanent magnets. In this way inexpensive sensors can be realized with an open geometry. The main application area of such unilateral NMR concepts is in nondestructive analysis of large objects. In addition to static objects the stream lines in flowing liquids, granular media, and complex mixtures can be followed by NMR (flow NMR). The fields of flow NMR and unilateral NMR are addressed in particular in view of development and applications of the NMR MOUSE® (Mobile Universal Surface Explorer).

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