Phase change and cooling characteristics of microjets measured using microcantilever heaters

This paper reports novel microcantilever metrology tools to investigate free microjets emanating from a micromachined nozzle of diameter 10 μm. Microcantilevers with an integrated resistive heater-thermometer were used to study microjet cooling and phase change characteristics. While the microcantilever heater was aligned to and impinged upon by hydrocarbon microjets, the heater temperature was modulated by a constant voltage source. Successive heating and cooling cycles captured the microjet phase change hysteresis properties. When the microcantilever heater temperature was controlled, it was possible to construct a full boiling curve. Measurements were made on microjets of butane, hexane, and octane. The convective heat fluxes accompanied by microjet impingement boiling were 2.9–7.6 kW/cm² for heater temperatures of 25–350 °C. Overall, the techniques reported herein show promise for characterizing microscale jet flows.