Phase change and cooling characteristics of microjets measured using microcantilever heaters

Abstract

This paper reports novel microcantilever metrology tools to investigate free microjets emanating from a micromachined nozzle of diameter 10 mu m. 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/cm(2) for heater temperatures of 25-350 degrees C. Overall, the techniques reported herein show promise for characterizing microscale jet flows. (C) 2008 Elsevier B.V. All rights reserved.