Though aerospace maintenance is currently a costly and time-consuming process, a new method for 3D printing sensors directly onto aerospace components could help to optimise the process.
Optomec aerosol jet technology, which is currently being developed by Swansea University, has enabled researchers to print strain and optical creep sensors directly onto the surface of jet engine compressor blades. They were able to determine a component’s degree of creep (tendency of solid materials to move or deform under mechanical stresses) to within 10mm using optical light measurement and a laser inspection system.
The condition of the blades can there be monitored in real time, meaning, according to the Welsh Centre for Printing and Coating (WCPC), increases in fuel efficiency and higher engine running temperatures.
During the sensor printing process, a mist generator is first used to atomise a special conductive nano-silver ink, with its conductive nano-particles then refined by a virtual impactor. Using a flow guidance deposition head, the resulting material stream is then aerodynamically focused, creating an annular flow of sheath gas which collimates the aerosol.
The coaxial flow that exits the flow guidance head through a nozzle directed at the substrate focuses the material stream to a tenth the size of the nozzle orifice (10 µm). CNC commands then position the flow guidance head, with the substrate remaining fixed, creating the patterning of the material, with a 5mm standoff distance between the deposition and the substrate ensuring that the material is accurately deposited onto non-planar substrates, into channels and over existing structures.
A thermal post treatment, using a spray which allows the materials to better resist high temperatures, then follows the depositing of the ink, ensuring its adhesion to the substrate as well as giving the sensor the correct conductive and mechanical properties required.
The researchers are also investigating the possibility of locally processing the deposition with a laser treatment, allowing substances with very low temperature tolerances to be used and an end result of a high-quality film as fine as 10nm.
Although the researchers are currently using nano-silver ink, stable up to 250°C, they are also looking into developing nano-platinum ink, which would remain stable up to 1200°C, therefore working with higher temperature components. This could be a crucial development, as sensors with high-temperature capabilities are a major requirement in the aerospace industry.