Structural Color Sensors: Tracking the Thermal History of Materials
The engineering of non-destructive, low footprint optical sensors has attracted significant interest in research in recent years. Such devices can enable real-time and spatiotemporal tracking of materials properties even in secluded applications, such as offshore wind turbines, or extreme environments, as found in thermal solar collectors.
Researchers at ETH Zürich have developed a novel thermal sensor based on structural color that provides direct optical feedback of materials properties such as hardness and resistivity. The sensor can be used at high temperatures (1000 °C) and allows the continuous detection of changes in refractive index larger than 1%.
The research is described and now featured on the inside cover of external pageAdvanced Optical Materials.
The technology transfer office of ETH Zürich has protected the intellectual property relating to this project and is exploring commercialization opportunities.
To demonstrate the new sensor concept on a real-world material, the researchers have optically tracked the thermal history of TiAlN coatings, a state-of-the-art coating material in wind-turbine engines.
The monitoring concept relies on a lossy Gires-Tournois interferometer configuration using thermally induced detuning of a highly absorbing state in the optical spectrum as sensor feedback. The displacement of the absorbing state is directly proportional to thermally induced changes in hardness and resistivity in the material. For the specific case of TiAlN coatings, such detuning is due to a symmetry-breaking structural phase transition, which is accompanied by the formation of saturated structural colors visible by eye.
Publication:
Structural Color Sensors with Thermal Memory: Measuring Functional Properties of Ti‐Based Nitrides by Eye
V. Schnabel, R. Spolenak, M. Döbeli, H. Galinski, Advanced Optical Materials 2018, 6, 1800656. external pageDOI:10.1002/adom.201800656