Mobile and Compact NMR

Abstract

NMR with mobile and compact devices is experiencing considerable growth in recent years in particular since instruments have become available, which are capable not only of measuring NMR relaxation but also images and highresolution spectra. Based on permanent magnet technology, compact tabletop NMR instruments measure samples of materials and solutions positioned inside the magnet, while compact mobile instruments measure material properties of intact objects and samples nondestructively in the inhomogeneous stray field outside the magnet. Following a brief introduction to NMR with homogeneous and inhomogeneous magnetic fields and to the concepts of permanent center-and stray-field NMR magnets, the evolution of the technology over the past 10 years is reviewed and illustrated with selected applications. Relaxation and diffusion measurements find use in the analysis of foods, biological tissues, polymer materials, porous media, and objects of cultural heritage. Compact imaging

Illustrating the quantum approach with an Earth magnetic field MRI

“…To our knowledge, few people are involved in developing MRI hardware based on the Earthʼs magnetic field: Callaghanʼs group at Victoria University of Wellington (New Zealand) [6][7][8] and Mohorič, a member of Stepisñikʼs group at the University of Ljubljana (Slovenia) [9,10], constitute a list which is not exhaustive. We might also mention the Polymer Gel Group at the Technical University of Bremen (Germany) [11] and the groups from Aachen (RWTH and Jülich) [12,13], for their well-known instrumental development. The educational community is growing: not only are companies such as Phywe (Göttingen, Germany), dedicated to turnkey student practicals, making the 0.5 T Compact-MRTR ® , interested in such devices, but also scientific instrument manufacturers, such as Thermo Scientific (Waltham, MA, USA), selling the PicoSpin ® , also with a permanent stray field, up to 1.8 T, for NMR spectrometers, and NMReady (Calgary, AL, Canada), offering research and training solutions for the classroom, with a 1.4 T static magnet including a frequency drive lock, are now presenting competing solutions.…”

The use of time domain 1H NMR to study proton dynamics in starch‐rich foods: A review

“…Due to the magnetic field inhomogeneities, structural information on the chemical makeup of a sample cannot be provided. However, the NMR signal decay following excitation by a radio‐frequency (RF) pulse is useful in applications requiring information on relaxation, diffusion, or other related phenomena (Blümich, 2016). The technique has a wide range of applications in the food industry justifying the numerous review articles that have been published on the subject in recent years (Blümich, 2019; Colnago et al., 2021; Kirtil & Oztop, 2016; Ozel & Oztop, 2021; Rodríguez‐Alonso et al., 2019; Yao et al., 2022).…”

Aging of polymeric materials by stray‐field NMR relaxometry with the NMR‐MOUSE

“…It relates to chain stiffness and the free volume and can be probed by measuring NMR relaxation. For such studies, compact tabletop and portable instruments are available . A portable NMR relaxometry sensor for nondestructive testing is the NMR‐MOUSE (MObile Universal Surface Explorer), which measures the NMR relaxation from a thin slice within an object exposed to the stray‐stray field of a permanent magnet (Figure ) .…”

“…By moving the sensor, different sections of the object can be probed, and discrete depth profiles can be measured with the spatial resolution determined by the slice thickness when the sensor is moved away from the object in small steps. These profiles report the stratigraphy of a layered object and the material properties of the layers in terms of the 1 H spin density, the 1 H NMR relaxation times T 1 and T 2 , and the self‐diffusion coefficient of solvents in the material …”