NMR MOUSE

G. Eidmann, R. Savelsberg, P. Blumler, B. Bliimich 1996, (The NMR-MOUSE, A mobile universal surface explorer), J. Magn. Reson. A122, 104-109. 

R. Haken, B. Bliimich 2000, (Anisotropy in tendon investigated in vivo by a portable NMR scanner, the NMR-MOUSE), J. Magn. Reson. 144, 195-199. 

Since it was proposed in the early 1980s [6, 7], spin-relaxation has been extensively used to determine the surface-to-volume ratio of porous materials [8-10]. Pore structure has been probed by the effect on the diffusion coefficient [11, 12] and the diffusion propagator [13,14], Self-diffusion coefficient measurements as a function of diffusion time provide surface-to-volume ratio information for the early times, and tortuosity for the long times. Recent techniques of two-dimensional NMR of relaxation and diffusion [15-21] have proven particularly interesting for several applications. The development of portable NMR sensors (e.g., NMR logging devices [22] and NMR-MOUSE [23]) and novel concepts for ex situ NMR [24, 25] demonstrate the potential to extend the NMR technology to a broad application of field material testing. 

B. Bliimich, V. Anferov, S. Anferova, M. Klein, R. Fechete, M. Adams, F. Casanova 2002, (Simple NMR-Mouse with a bar magnet), Concepts Magn. Reson. 15 (4), 255-261. 

Fig. 9. Schematic of the NMR-MOUSE. Samples are placed on top of the surface coil located between the two permanent magnets.

By far the most widespread use of NMR in an on-line production environment is the utilization of downhole exploration tools by petroleum service companies such as Schlumberger, Halliburton, and Baker Hughes. Articles on these unilateral NMR systems are found in the patent databases, " academic literature, and on-line resources provided by the exploration companies. The references provided here are just a few examples in a very prolific field. The technique is applied in high-temperature and pressure situations and currently is used down to a depth of about 10 km (6 miles) to produce a picture of water/oil content in the adjacent rock formations as well as to derive permeability, diffusivity, and hydrocarbon chemistry information. Mobile unilateral NMR systems such as the NMR-MOUSE are also being developed in order to take benchtop NMR systems into the field to perform analysis of geological core samples at the drill site. NMR analyzers are also being developed to determine the bitumen content and properties in tar sand production and processing. " " ... 

A.M. Haiduc, E.E. Trezza, D. van Dusscboten, A.A. Reszka, and J.P.M. van Duynboven, Non-invasive through-package assessment of the micro structural quality of a model food emulsion by the NMR MOUSE, LWT- Food Sci. TechnoL, 40, 737-743 (2007). 

Figure 7.15 T2 weighted images of car-tyre sections showing in each image the tread (left) and the base with polymer fibers (right) (a) Hard base, (b) Soft base. The overlaid curves are T2 data measured as a function of depth by the NMR-MOUSE (see Section 7.3.1)...

The NMR-MOUSE is a portable NMR sensor which works in highly inhomogeneous magnetic fields. Because of field inhomogeneity NMR spectroscopy of the chemical shift is not readily possible, but relaxation times and parameters of translational motion can be measured by echo techniques. These are the most important NMR parameters which are exploited for contrast in imaging. Unless fluids are investigated field inhomogeneities are essentially no obstacle for relaxation analysis [80], because molecular motion by translational diffusion is absent. 

Figure 7.22 The NMR-MOUSE (a) Schematic. The NMR sensor consists of an u-shaped permanent magnet with a solenoidal rf coil placed in the gap. (b) Photo of the NMR-MOUSE testing a tyre, (c) Example of a train of successive Hahn echoes generated according to Carr, Purcell, Meiboom and Gill (CPMG echo train) for carbon-black filled SBR measured by the NMR-MOUSE. The time constant of the echo-envelope defines T...

Some selected applications of the NMR-MOUSE to elastomers are summarized in Figure 7.23. In (a) T2 has been measured for a series of carbon-black filled NR samples... 

Figure 7.23 Applications of the NMR-MOUSE to elastomer materials (a) T2 values for a curing series of carbon-black filled NR. Comparison of values obtained at high homogeneous field (DMX 300) and with the NMR-MOUSE, (b) cross-link series of unfilled SBR with different sulfur content, (c) T2 versus glass-transition temperature Tg of unfilled SBR by the CPMG and the steady-state CPMG methods, (d) normalized Hahn-echo decay curves for poly(butadiene) latex samples. Different decay rates are obtained for small medium and large cross-link densities...

In elastomer samples with macroscopic segmental orientation, the residual dipolar couplings are oriented as well, so that also the transverse relaxation decay depends on orientation. Therefore, the relaxation rate 1/T2 of a strained rubber band exhibits an orientation dependence, which is characteristic of the orientational distribution function of the residual dipolar interactions in the network. For perfect order the orientation dependence is determined by the square of the second Legendre polynomial [14]. Nearly perfect molecular order has been observed in porcine tendon by the orientation dependence of 1/T2 [77]. It can be concluded, that the NMR-MOUSE appears suitable to discriminate effects of macroscopic molecular order from effects of temperature and cross-link density by the orientation dependence of T2. 

Figure 7.25 One-dimensional imaging with the NMR-MOUSE (a) Single-point imaging sequence for phase-encoding of space, (b) drawing of the NMR-MOUSE with coils for pulsed field gradients, (c) sample of an elastomer sheet with parallel textile fibres and one-dimensional NMR image with the space direction perpendicular to the fiber direction...

A. Guthausen, Die NMR-Mouse Methoden und Anwendungen zur Charakterisicrung von Polymeren, RWTH-Aachen, 1998. [Ph. D. Thesis]... 

Quality tests are usually performed using bench-top, low filed NMR spectrometers. Volume-average properties are determined with this equipment. Surface layer of samples can be analysed using recently developed NMR-MOUSE (mobile universal surface explorer) [26, 188]. The NMR-MOUSE is a relatively small NMR device suited for the investigation of surface-near volume elements. Lateral surface heterogeneity of elastomeric materials can be scanned with this device. Possible applications of the NMR-MOUSE for the characterisation of rubbery materials were demonstrated [26,189-191]. 

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