Nanoscale hot-wire probe for supersonic flow measurments

The heat transfer response of a nanoscale thermal anemometry probe (NSTAP) was investigated in supersonic conditions. The fabrication of the platinum based NSTAP hot-wire was conducted using standard semiconductor manufacturing techniques. Measurements of the sensor’s thermal response using a constant current anemometer shows a response time an order of magnitude smaller than classical cylindrical hot-wires. The critical role of the supporting structure of the sensing element was attested by modifying the metal composition of the studs to reduce the heat loss from Joule effect outside the sensing element, modifying the temperature profile along the sensing element. The addition of a gold layer on top of the platinum layer enabled a considerable reduction of the response time leading to 33 ms. Increasing the cutoff frequency by concentration of the heat transfer in the nano-ribbon element provides the possibility to explore the relationship between geometrical characteristics of the sensor and Nusselt dependence on Mach number in rarefied gas.