Key findings
When engineers design a new aircraft, they need to know exactly how air flows over every surface. The pressure distribution must be controlled or the fuel efficiency, handing, or even structural safety can be affected.
A promising new technique for measuring this is by applying a special paint to scale models tested in wind tunnels, which glows in proportion to the air pressure pushing against it. However, these paints have one main flaw – they’re sensitive to temperature as well as pressure. As a model heats up during testing, the paint output can shift and introduce errors that engineers then have to unpick.
Now, a team from The University of Manchester’s Departments of Mechanical and Aerospace Engineering, and Chemistry, have created a paint that substantially reduces the problem. This new material uses a light-emitting, platinum-based compound, locked into a specially engineered plastic. The results of trials using the paint, published in ACS Applied Engineering Materials , show a drop in temperature sensitivity to just 0.3% per degree Celsius – 25% less than the current industry benchmark.
Dr Elliott Nunn, first author based in the Department of Chemistry, The University of Manchester, said: “When you’re testing a vehicle at high speed it can heat and cool dramatically based on its aerodynamic design. By creating a pressure-sensitive paint which doesn’t respond as strongly to this heat, we’ve got something that’s much closer to measuring exactly what we want to measure. Our hope is that this will really help the engineers designing the next generation of high-performance and more sustainable aircraft and spacecraft, to make better-informed decisions through cleaner data.”
Their breakthrough comes down to how the active ingredient sits within the material. In many existing paints, the molecules responsible for glowing can cluster together, and this clustering makes the paint more sensitive to heat. The Manchester team fixed this by anchoring this ingredient, from the same family of molecules that give blood its red colour, or make leaves green, directly into a tough, Teflon-like plastic. When held in place at the chemical level, the molecules are far less likely to cluster and the paint’s temperature sensitivity drops.
Dr Louise Natrajan, Reader in the Inorganic Chemistry Group, The University of Manchester, said: “Getting this chemistry right was thanks to a creative collaboration between our chemistry group and the aerospace engineering team – basically, they knew what the paint needed to do in a wind tunnel, and we knew how to create something that could do it.”
To test their paint under realistic conditions, the team applied it to a cone-shaped model designed to produce complex airflows, then ran this model through a supersonic wind tunnel where airflows can exceed Mach 5 – 5x the speed of sound. At these conditions the model’s temperature varies drastically across its surface. However, the new paint measured pressure accurately throughout the test, with results aligning closely with the values predicted by computer simulations.
This paint was also able to help the researchers visualise the corkscrew-shaped swirls of air that develop along concave curved surfaces – known as Görtler vortices – which are important for understanding how the thin layer of air next to a surface behaves at speed.
More accurate pressure measurements at high speeds and temperatures, could translate directly into helping the aerospace industry to develop safer, more efficient transport. The team are now planning to test their paint across a wider range of conditions, to build confidence in how reliably it can perform.
This research has been published in the journal ACS Applied Engineering Materials
Full title: Low-Temperature Dependency Pressure-Sensitive Paints for Wind Tunnel Testing Based on Luminescent Polymer-Bound Porphyrins
DOI: 10.1021/acsaenm.6c00751
URL: https://doi.org/10.1021/acsaenm.6c00751
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ACS Applied Engineering Materials
Low-Temperature Dependency Pressure-Sensitive Paints for Wind Tunnel Testing Based on Luminescent Polymer-Bound Porphyrins
16-Jul-2026