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This paper reports on the fabrication and characterization of liquid and gaseous jets ejected from microfabricated nozzles with dimensions ranging from 500 nm to 12 μm. Unlike previous work reporting the fabrication of nano-orifices defined within the thickness of the substrates [1-4], the in-plane nanonozzles presented in this paper are designed to sustain the high pressures necessary to obtain substantial nanofluidic jet flows. This approach also allows important three-dimensional features of nozzle, channel and fluidic reservoir to be defined by design and not by fabrication constraints, thereby meeting important fluid-mechanical criteria such as a fully-developed flow. The shrinking jet dimensions demand new metrology tools to investigate their flow behavior. A laser shadowgraphy technique is used to visualize and image the jet flows. Micromachined heated and piezoresistive cantilevers are used to investigate the thrust and heat flux characteristics of the jets.

This paper reports novel microcantilever metrology tools to investigate free microjets emanating from a micromachined nozzle having 10 μm diameter. Microcantilever sensors are well-suited to interrogate these flows due to their high spatial and temporal resolution. In this work, microcantilevers with integrated piezoresistors have been used to detect the breakup distance of free microjets, and microcantilevers with integrated resistive heaters have been applied to study microjet cooling and phase change characteristics. Measured microjet thrusts were in the range of 10 – 60 μN and heat fluxes were measured in the range of 25 – 350 °C. The convective heat fluxes by microjet impingement boiling were estimated at 2.9 – 7.6 kW/cm2. The techniques reported herein are promising to characterize microscale flows.