The profile NMR-MOUSE® is a non-destructive sensor that combines the strengths of time-domain NMR with microscopic spatial resolution. Thanks to its compact size, the system is portable, and its open sensor geometry allows for the measurement of spin densities, relaxation times, and self-diffusion coefficients in samples of any size. With a fully-automated positioning unit, spatially resolved profiles can be easily obtained. Given its low weight and small dimensions, the system can be conveniently brought to the object of interest. This powerful NMR-MOUSE® profile probe seamlessly integrates with the Kea spectrometer.
The Profile NMR-MOUSE sensor employs a permanent magnet geometry that creates a flat sensitive volume parallel to the scanner surface. To both excite and detect the NMR signal from this volume, a surface RF coil is positioned on top of the magnet at a location that determines the maximum penetration into the sample. As this sensitive slice is moved across the object, this one-sided NMR scanner generates one-dimensional profiles of the sample structure with a spatial resolution as fine as 10 µm. Different models of the Profile NMR-MOUSE are available, offering varying maximum measurement depths and resolutions to suit different needs.
Get in touch with us to discuss which model is the most suitable for your application!
The sensor operates on the same principles as clinical Magnetic Resonance Imaging (MRI). In this method, hydrogen molecules are detected using radiofrequency waves, and the amplitude of the response signal directly corresponds to the quantity of hydrogen nuclei within the examined volume. Furthermore, the decay time of the signal provides valuable insights into molecular mobility. To perform the measurement, the sensor is either placed adjacent to the object’s surface or the sample is positioned atop the sensor, depending on the object’s size.
The high-precision lifting mechanism automatically moves the sensor to collect profiles at various depths. The accompanying figure illustrates the sensor’s starting position at the lowest point (1) within the scanning range, with the sensitive volume situated at the surface of the sample. As the sensor is raised (2 and 3), the position of the sensitive volume shifts to enable measurements at different depths.
profile NMR-MOUSE Models
A Profile NMR-MOUSE system comprises three main components: the NMR-MOUSE sensor itself, the high-precision lift unit, and the electronics console.
Because various applications come with distinct demands in terms of measurement depth, spatial resolution, and gradient strength, a range of different NMR-MOUSE sensor models is available to accommodate these diverse requirements.
The table below gives an overview of the different available models.
Get in touch with us to discuss which model is the most suitable for your application:
Water transport in concrete
The profile NMR-MOUSE is a versatile tool capable of monitoring water transport in dynamic processes, such as water absorption or drying in concrete samples. In the presented example, we observe the ingress of water into a 5 mm thick concrete specimen. Water is applied to one side of a dry concrete sample, and over time, we can track the progression of water infiltration into the material. After 50 minutes, the concrete sample reaches saturation, as evidenced by a consistent moisture content across the entire sample.
The figure on the right illustrates moisture profiles obtained from a 5 mm thick concrete sample during a drying process. Notably, it showcases how the amplitude of the initially uniform profile, observed in the saturated sample, gradually decreases from the edges toward the center until it stabilizes to match the ambient room humidity.
Absolute water content measurement
Water content is a critical parameter in both the production process and the long-term performance of building materials. Traditional methods for measuring water content are often destructive and lack the ability to provide spatial information about water distribution within a sample. The profile NMR-MOUSE employs a technique similar to that used in clinical MRI machines, offering a non-invasive means of measuring water content with high spatial resolution.
The figure illustrates a correlation between moisture content measured using the profile NMR-MOUSE and moisture content determined by weight. Notably, the data demonstrates a high degree of linearity, particularly in concrete materials formulated with various types of aggregates. This correlation underscores the reliability and accuracy of the profile NMR-MOUSE in quantifying water content within construction materials.
Penetration depth of water repellent treatments
Water repellent treatments applied to facades play a crucial role in preventing moisture absorption by mineral building materials. Traditionally, these treatments involve saturating the facade with a hydrophobic agent. The effectiveness of such treatment depends significantly on the depth to which the hydrophobic agent penetrates the material. Traditionally, this penetration depth is determined through destructive methods involving the extraction of a bore core from the facade, followed by a visual inspection to assess the presence of the hydrophobic agent.
The profile NMR-MOUSE introduces a non-destructive alternative for measuring the spatial distribution of the hydrophobic agent within the facade. The figure presented illustrates profiles taken both before and after the application of the treatment and subsequent saturation of a concrete sample with water. This technology enables clear visualization of the penetration depth achieved by the hydrophobic agent and its impact on water saturation within the material.
By providing a non-invasive means of assessing the distribution and effectiveness of water repellent treatments, the profile NMR-MOUSE offers a valuable tool for optimizing and monitoring the performance of these treatments in preserving the integrity and durability of building facades.
Measurements during Freeze-Thaw Cycles
The deterioration of concrete structures exposed to the combined effects of freeze-thaw cycles and deicing salt attack is a significant concern, especially in cold climates. Before visible damage occurs, concrete subjected to these conditions experiences rapid moisture uptake, a phenomenon referred to as frost suction. Understanding the distribution of water within the concrete during freeze-thaw cycles is crucial for assessing its vulnerability and durability. The PM25 is a valuable tool for monitoring changes in water content in this context, allowing for the identification of physically bound water and water located in capillary and mesopores.
Figure a) shows the total amount of liquid water during a freeze thaw cycle while Figure b) shows the fraction of physically bound and pore water.
Moisture detection in polymer composites
The intrusion of liquids coming into contact with an object’s surface serves as a notable instance of sample alteration. Even minute quantities of solvent can induce substantial changes in material properties, all of which can be discerned through the utilization of mobile unilateral NMR sensors. In this particular study, we monitored the absorption of water within a polymer composite over time. Initially, a 3 mm thick sample underwent a drying process in an oven, followed by immersion in water at room temperature. A series of profiles were recorded relative to the duration of exposure to water (Figure a). These profiles were generated by scanning the sample at a resolution of 200 µm, with the amplitude assigned to each position determined by aggregating echoes acquired during a solid-echo train.
The vertical scale was then converted into water content (expressed as a percentage by weight) through gravimetric calibration. It’s important to emphasize that the variation in signal intensity within the profiles is attributable to an increase of the T2eff of the material, which is influenced by the presence of water. This enables the indirect quantification of minuscule amounts of water, including those case where the water signal itself is below the detectable limit. The findings underscore the technique’s applicability in tracking the infiltration of solvents into robust materials, and its sensitivity is adequate for detecting even ambient humidity-induced moisture within the sample. Figure (b) offers a comparison between the profile of the dried sample and that of a sample exposed to room-temperature air humidity for an extended period. The profile indicates that the sample contains approximately 1% moisture, which is distributed almost uniformly throughout its thickness.
Non-destructive characterization of paintings
Solvent Ingress into Polymers
The profile NMR-MOUSE® technique proves to be a valuable tool for investigating transport processes across material surfaces, particularly in cases involving the penetration of solvents into solid materials. An illustrative application of this technique is in the examination of fuel tank walls, which comprise a multi-layer structure consisting of two layers of polyethylene (PE) separated by a barrier layer of ethylene vinyl alcohol copolymer (EVOH). This design serves to prevent the diffusion of volatile compounds through the tank wall. The barrier layer is then bonded to the two polyethylene plates using two thin layers of resin.
The graph presents a profile of the tank wall, as measured with the profile NMR-MOUSE at a resolution of 50 µm. It took approximately two hours to complete one full profile measurement. Notably, the profile allows for the clear identification of the different layers constituting the tank wall.
To demonstrate the effectiveness of the barrier layer, the study tracked the diffusion of gasoline from inside the tank wall. This was achieved by exposing the regrind side of the tank to gasoline (RON 91) and recording profiles of the tank wall at various intervals. The profiles reveal the progression of the diffusion front into the PE layer, which ultimately halts at the barrier layer. After 163 hours, gasoline saturation is achieved on the regrind side, while the barrier layer effectively shields the other side, leaving it nearly unaffected.