The Gañán-Calvo method for utilizing a “virtual nozzle” to
produce very small diameter columnar liquid jets is currently the state of the
art in the field. This method involves passing a gaseous fluid entraining a
liquid fluid through a capillary tube and out an aperture at the end. The
gas-dynamic forces exerted by the gaseous fluid provide the “virtual nozzle”
that reduces the liquid flow diameter well below that of the aperture diameter.
While the Gañán-Calvo method improves markedly over conventional solid walled
converging nozzles by offering reduced liquid flow diameters and reduced
incidence of clogging, it cannot render droplet diameters in the
micrometer/sub-micrometer range.
Researchers at Arizona State University have developed an
improved Gas-Dynamic Virtual Nozzle (“GDVN”) that refines the Gañán-Calvo method
to produce superior columnar liquid jets. Specifically, the ASU GDVN offers
significantly smaller capillary, orifice, and droplet dimensions, single-file
microscopic streams, in situ alignment, and miniaturization. Likewise, the ASU
GDVN can run the flow through a second capillary before or instead of a
conventional aperture. The ASU GDVN is particularly useful for applications
where the liquids of interest are complex aqueous solutions containing
macromolecules or biospecies due to the increased risks of clogging that result
when converting these particles to micrometer sizes.
Potential Applications
- Experimentation (e.g. Diagnosis, Analysis, Measurement)
- Micro-fluidic Engineering (e.g. Biological, Chemical,
Material)
- Industry (e.g. Automobile, Food Production)
- Environment
- Energy
Benefits and Advantages
- Smaller Capillary, Orifice, and Droplet Dimensions –
operates at capillary and orifice diameters down to 0.02 mm compared to 0.05 –
2 mm and produces micron diameter droplets compared to 10.7 micron droplets
- Single-File Microscopic Droplet Stream – generates
single-file droplet streams for high levels of precision where competing
methods generate sprays
- In Situ Alignment of Capillary and Orifice – seals
mechanical or piezoelectric drives within the GDVN assembly that adjust the
capillary with respect to the orifice
- Microthread Injection Adaptability – offers ability to
inject microthreads via combinations of capillaries or capillaries and
apertures to minimize overshoot, turbulence, or back eddying in the flow
- Miniaturization – facilitates differential
pumping
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