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Publication Date: 2016-Feb-03
Document File: 7 page(s) / 301K

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The Prior Art Database

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I.          Background

This article discloses a new ion source based on a planar microfluidic geometry, which may be utilized for mass spectrometry (MS) and other analytical techniques entailing the ionization of a sample to be investigated.    

Conventional pneumatic and pneumatically-assisted ion sources for mass spectrometry comprise concentric tubes in which a liquid analyte is delivered through the inner tube, and a gas is delivered through the annular space between the inner tube and a surrounding outer tube.  See, e.g., Fischer SM and PC Goodley. “Micro concentric tube nebulizer for coupling liquid devices to chemical analysis devices.” Patent 5,752,663, 19 May 1998; Doak RB, Spence JCH, Weierstall U, Deponte D, Starodub D, Warner JS. “Gas dynamic virtual nozzle for generation of microscopic droplet streams.” Patent 8,272,576, 25 Sep 2012.  The outlet of the inner tube can be within the outer tube or extend beyond the outlet of the outer tube.  Variations also can include tapering of the exterior surface of the outlet end of the inner tube and/or the interior surface of the outlet end of the outer tube to form a converging nozzle.  At the location where the liquid and gas flows come into contact with each other, the liquid flow is accelerated by shear forces exerted by the gas flow and breaks up into droplets.  This breakup process can occur either before or after exiting the outer tube depending on the geometry of the ion source and the liquid and gas flow rates.

Droplet systems (e.g., aqueous-fluorocarbon emulsions) for high-throughput sample handling, in which samples are separately contained in individual droplets, are most commonly and most practically implemented in planar microfluidic formats.  Interfacing droplet systems to mass spectrometers thus requires fluidic connections between planar devices and the cylindrical capillaries that comprise the ion sources described above.  These connections often result in undesired merging or splitting of droplets moving between the droplet-generating device and the ion source, which can compromise the goal of isolating different samples in individual droplets.

II.        Solution                                                               

To address the problems discussed above, this article proposes a new ion source having a planar microsprayer geometry.  The planar microsprayer may be implemented as a microfluidic chip that nebulizes liquid samples for input to a mass spectrometer.  In some applications, the spray produced by the proposed planar microsprayer may be subjected to an electric field generated by known techniques to form an electrospray.

The planar microsprayer disclosed here can be constructed using standard microfabrication techniques to allow seamless integration of the ion source with other microfluidic components in a...