Fraunhofer Institute for Mechanics of Materials IWMThe NextLevel project aimed to exploit the new possibilities offered by quantum sensor technology in materials characterization and testing. Magnetic fields were detected by means of contactless measurements from outside, as they proved virtually impossible to shield. Nitrogen vacancy diamond sensors (NV) and optically pumped magnetometers (OPM) based on vapor cells were ideal for this purpose. The combination of these techniques opened up new ways of gaining insights into structural or functional inhomogeneities in mechanical and electrical materials as well as components.
Next Level LandBW 2024/25 – Quantum Sensors in Material Characterization and Testing
Completed research project
Project description
The optimization of materials, understanding fatigue, and preventing failures were crucial for many industries, including automotive, robotics, aerospace, and renewable energies. Magnetic fields had long been used as a tool for non-destructive testing. Until then, the focus had been on technically generated magnetic fields at or above the Earth's magnetic field strength (≈50 µT) for penetrating and monitoring materials and components. Recent advances in ultra-high-sensitivity magnetometers based on quantum mechanical systems—such as NV centers in diamond and optically pumped magnetometers (OPM)—had shifted research to much weaker fields. Both NV magnetometry and OPM were non-invasive and allowed magnetic fields to be measured without disturbing the system under investigation.
The Fraunhofer NextLevel project built on earlier research in the QMag project, in which various materials (ferritic steel, electrical steel, and pure iron) had been investigated using NV and OPM magnetometers. These quantum sensors enabled absolute magnetic field measurements and imaging at the microscale, revealing previously inaccessible magnetic structures. The NextLevel project aimed to leverage these capabilities for materials characterization and testing, including developing a next-generation magnetic field camera. This investigation led to a fingerprint concept for materials, assigning each sample unique magnetic signatures. Among other activities, the project investigated how these signatures could be grouped and correlated with material type and properties (phase transformation, stiffness changes, embrittlement). The goal was to develop methods for material improvements, fatigue detection, prediction, and prevention. The study of samples with varying degrees of fatigue enabled detection of fatigue patterns, characterization of fatigue-induced magnetic field changes, and insights into crack formation via specific magnetic microstructures.
Fraunhofer IWM subproject:
Micromechanical testing and material characterization with quantum sensors
In the Fraunhofer flagship project QMag, Fraunhofer IWM has expanded its expertise to include magnetic material testing on micro-samples using optically pumped magnetometers (OPM). In collaboration with Fraunhofer IPM, sensors and methods have been further developed and verified. Initial results on high-strength steels and electrical steel sheets were published in Koss et al. (2022) [1] and Philipp et al. (2023) [2] and presented at conferences. In addition, initial work with NV magnetometers was carried out with Fraunhofer IAF.
To interpret the quantum sensor signals, Fraunhofer IWM also conducted micromagnetic simulations that replicated material magnetic field changes. Finite element and finite difference methods were used to map mechanical and magnetic stresses and their combined effects. The goal was to achieve a reliable, reproducible understanding and representation of defect- and plastic-damage-induced material changes in both experiments and simulation models.
AP2: Magnetometry for characterizing and testing materials
- Obtained information about magnetic domain and subdomain structures as well as microstructural magnetization behavior with OPM and NV on various unfatigued materials (FeSi, Fe)
- Evaluated the development of plastic damage with quantum sensors (OPM and NV) and investigated material samples with different degrees of fatigue
AP3: Materials analysis for a case study: Shape memory alloys (pseudoelasticity)
Produced and prepared samples from a shape memory alloy (NiTi)
- Performed quasi-static and cyclic tensile tests on shape memory alloys
- Evaluated their magnetic signatures with OPM and NV
[1] Koss, P. A.; Durmaz, A. R.; Blug, A.; Laskin, G.; Pawar, O. S.; Thiemann, K.; Bertz, A.; Straub, T.; Elsässer, C., Optically pumped magnetometer measuring fatigue-induced damage in steel, Applied Sciences 12/3 (2022) Art. 1329, 11 Seiten Link
[2] Philipp, S.; Mathes, N.; Feuerhelm, M.; Durmaz, A. R.; Deldar, S.; Soldativ, I.; Schäfer, R.; Vidal, X.; Straub, T., Diamond-based magnetic widefield-microscopy of domain patterns in electrical steel, Proc. of SMSI 2023 – Sensor and Measurement Science International Conference; AMA Verband für Sensorik und Messtechnik e. V. (Hrsg.); AMA Service GmbH, Wunstorf (2023) 75-76 Link
Transfer of project results to the following Fraunhofer IWM R&D services for companies:
- Characterization of the microstructure of materials, both during production and in quality assurance, as well as in the application and improvement of component service life
- Materials optimization for medical devices (e.g., stents, joint replacements), aerospace, robotics, or fusion reactors
