Development of pressure sensitive molecular film as a measurement technique for micro-and nano-devices

Gas flows in micro- and nano-systems having high Knudsen number must be treated as molecular flows, and experimental analyses of thermo-fluid phenomena in micro- and nano-systems need measurement techniques employing "molecular sensors". However, such measurement techniques are behind in development compared with molecular simulation techniques for numerical analyses. Pressure sensitive paint (PSP) technique is based on the interaction of oxygen molecules with luminescent molecules, and it seems suitable for analyses of high Knudsen number flows, which require diagnostic tools in the molecular level. In this study, we fabricate pressure sensitive molecular films (PSMF) with very small thickness based on the PSP technique and the Langmuir-Blodgett (LB) film technique. It is clarified that the PSMF composed of palladium (II) mesoporphyrin IX (PdMP) as a luminophore and arachidic acid as a buffer has comparable pressure sensitivity with conventional PSPs in low pressure regime with high Knudsen number, even if the amount of the luminescent molecules in the PSMF layer is much smaller than that in conventional PSPs. The results indicate the feasibility of PSMF technique for pressure measurement in high Knudsen number flows such as micro flows.