Construction of bi-layer biluminophore fast-responding pressure sensitive coating for non-contact unsteady aerodynamic testing

Herein we report on a biluminophore fast-responding pressure sensitive coating with a bi-layer structure prepared by a non-sensitive reference base paint and subsequently a classic polymer-ceramic pressure sensitive paint (PSP). The coating procedure is fully sprayable and allows the separation of the two luminophores in each layer to prevent their interference that may affect the pressure responsibility. The major advance is the use of solgel process of tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES) to make the bottom reference layer which ensures the spreading and affinity of the top PSP, composed of a room-temperature vulcanizing silicone rubber (RTV), so that very thin PSP layer, i.e. less than 5 mu m was achieved. Besides, silane-functionalized carbon dots (CDs) was selected as the reference probe, for it could be well-incorporated with the TEOS/MTES matrix, and gained high loading level and hence strong luminescence of the basecoat to overcome the attenuation effect of the top PSP layer. The resultant biluminophore bi-layer fast-responding PSP (denoted as Fast bi-PSP) showed two completed separated emissions with lambda(max) at 430 and 600 nm for the incorporated CDs and the oxygen sensitive ruthenium complex dye, which enables the utility of intensity ratio from blue and red luminescence for the measurement of surface pressure by following Stern-Volmer relationship. Using a shock tube, the response time of the Fast bi-PSP coating was determined to be 0.4-0.6 ms according to the chemical composition. The ability of the coating for monitoring the dynamic evolution of full-field surface pressure was demonstrated on sample plates at attack angles of 0 degrees and 5 degrees. Our work suggests a facile but efficient way for the future design of self-referenced photoluminescent non-contact surface pressure sensing systems.