Microfluidics for generation and characterization of liquid and gaseous micro- and nanojets

This paper reports a microfluidic system for the generation and characterization of liquid and gaseous micro- and nanojets. The system comprises in-plane silicon micro/nanonozzles with dimensions ranging from 500 nm to 12 μm, a micro-to-macrofluidic interface and package, and a high pressure delivery source allowing microfluidic flow at pressure drops up to 15 MPa (2200 psi). Further, the system possesses the ability to characterize the jets by use of both shadowgraphy and impinging cantilever techniques. Unlike previous work reporting the fabrication of nano-orifices defined within the thickness of the substrates [1], [2], [3] and [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.