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Universal Fluid Droplet Ejector

SLAC National Accelerator Laboratory

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Technology Marketing SummaryStanford researchers have developed a patented, economical fluid droplet ejector that is capable of varying the vertical and horizontal inter-droplet spacing of a two-dimensional droplet array in real time. This universal design is compatible for a wide variety of fluids because it can be manufactured with a material and process that enables the device to be both chemically inert and biologically sterile. It also utilizes a micro-machined aperture and thermally fused components for easy of manufacturing and to enable mass production. The ejector can produce droplets from 5 to 100 microns in diameter at a rate up to several hundred hertz. The issued patent details the design's suitability for several physical, chemical and biological applications including: droplet analysis experiments, aerosol characterization, material deposition and cell-sorting applicationsDescriptionA fluid ejector capable of producing micron sized droplets on demand is constructed of: a quartz tube; a donut shaped piezoelectric element wrapped around one end of the tube and joined with the tube by high-strength epoxy; and a piece of silicon wafer with a micro machined orifice and heat-fused with the same end of the tube.  The orifice can be either conical or pyramidal in shape.  Its size and shape can be optimized for a particular application, depending on the type of fluid used, and the size of ejected droplets desired.  The layer of silicon dioxide which forms naturally on the surface of the silicon wafer allows the wafer to be fusion bonded to the flat bottom rim of the quartz tube when these two components are placed in physical contact and raised to a temperature of 600 deg C.  When energized, the piezoelectric element contracts in the mode which squeezes on the quartz tube, thus ejecting micron sized droplets through the orifice.  The use of inert and easily sterilized materials like silicon and quartz in the microdrop ejector allows applications with a wide variety of organic and inorganic fluids which may be corrosive or at high temperatures, or may require high levels of sterility.  These common materials also make it easy and inexpensive to mass produce ejectors with identical or different orifices for a variety of applications.  Fluid pressure can be controlled by a manometer which is filled either with air or an inert gas.

Applications of microdrop ejectors designed and fabricated as described include, but are not limited to, the following.  They can be used for the generation of aerosols for various studies, weighing macromolecules that are incorporated into such uniform droplets, microfabrication by accretion of material contained in the droplets in arbitrary geometry on a substrate, and ultra-high resolution inkjet printing.  A uniform array of ultra-fine droplets may provide the ideal environment for materials analysis using optical excitation as a probe.  Also, the droplets can be electrically charged to a uniform level by straightforward means.  Time-of-flight analysis of materials, for example, will then be possible.
  • Inexpensive
  • Chemically inert
  • Biologically sterile
  • Mass production possible
Applications and Industries
  • Aerosols
  • Microfabrication
  • Ultra-high resolution inkjet printing
More InformationPatent Issued: 5,943,075 (USA)Patents and Patent Applications
ID Number
Title and Abstract
Primary Lab
Patent 5,943,075
Universal fluid droplet ejector
A droplet generator comprises a fluid reservoir having a side wall made of glass or quartz, and an end cap made from a silicon plate. The end cap contains a micromachined aperture through which the fluid is ejected. The side wall is thermally fused to the end cap, and no adhesive is necessary. This means that the fluid only comes into contact with the side wall and the end cap, both of which are chemically inert. Amplitudes of drive pulses received by reservoir determine the horizontal displacements of droplets relative to the ejection aperture. The drive pulses are varied such that the dropper generates a two-dimensional array of vertically-falling droplets. Vertical and horizontal interdroplet spacings may be varied in real time. Applications include droplet analysis experiments such as Millikan fractional charge searches and aerosol characterization, as well as material deposition applications.
SLAC National Accelerator Laboratory 08/24/1999
Technology Status
Development StageAvailabilityPublishedLast Updated

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