In wind tunnels, engineers have for years struggled with one hidden interference: temperature distorts pressure readings on aircraft models. Conventional luminescent paints respond to both factors at once, and the error accumulates until a separate temperature sensor is introduced.
Chemists and engineers from the University of Manchester, together with colleagues from Eastern Finland, have created a molecule that separates the signals by itself. It emits red and blue light simultaneously. The red responds to both air pressure and temperature, while the blue responds only to temperature. By comparing the intensity of the two colours, the temperature interference can be subtracted instantly to obtain a pure pressure value.
At the heart of the molecule is a gold atom bonded to a ring-shaped compound, acridine. The position of the bond determines which colour the substance emits: one position gives pressure-sensitive red phosphorescence, the other gives temperature-dependent blue fluorescence. Calculations by the Finnish colleagues helped predict the behaviour even before synthesis in the laboratory.
The molecule is added to a special paint with which the aircraft model is coated. A camera records both colours simultaneously, and the ratio of the signals automatically corrects the data. There is no longer any need to attach additional temperature sensors, which complicate the experiment and create their own distortions of the flow.
According to Dr Alexander Romanov, such built-in self-correction was previously unavailable to conventional luminophores. Dr Mark Quinn notes that temperature correction remains one of the main problems when using pressure-sensitive paints, and a single-molecule solution looks more elegant and more practical under real testing conditions.
The work has been published in the journal Advanced Optical Materials and forms part of Manchester's programme to improve such coatings. In parallel, the scientists are developing platinum-based paints with low sensitivity to temperature. Together, these approaches bring closer the moment when designers will be able to obtain the most accurate pressure-distribution maps on new aircraft.
One molecule, two colours of light — and the accuracy of measurements in the wind tunnel improves without any extra equipment.
