Sheath flow methods
Inventors
Mott, David R. • Howell, JR., Peter B. • Ligler, Frances S. • Fertig, Stephanie • Bobrowski, Aron
Assignees
Publication Number
US-9649803-B2
Publication Date
2017-05-16
Expiration Date
2026-06-09
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Abstract
A sheath flow system having a channel with at least one fluid transporting structure located in the top and bottom surfaces situated so as to transport the sheath fluid laterally across the channel to provide sheath fluid fully surrounding the core solution. At the point of introduction into the channel, the sheath fluid and core solutions flow side by side within the channel or the core solution may be bounded on either side by the sheath fluid. The system is functional over a broad channel size range and with liquids of high or low viscosity. The design can be readily incorporated into microfluidic chips without the need for special manufacturing protocols. Uses include extruding materials and/or fabricating structures.
Core Innovation
The invention provides a sheath flow method and device comprising a channel with at least one fluid transporting structure located in the top and bottom surfaces of the channel. These structures transport the sheath fluid laterally across the channel to fully surround the core fluid flowing inside. At introduction, the sheath and core fluids flow side by side, but the fluid transporting structures cause the sheath fluid to flow above and below the core fluid, creating a fully encased core stream within the sheath stream. This method leverages laminar flow properties to maintain the core fluid's position centered in the channel.
Previous sheath flow designs faced challenges including difficulty in manufacturing annular sheath flows in microfluidic systems, complexity in controlling multiple sheath streams, and the inability to sheath the core fluid completely on all sides without complex fabrication processes such as stacking multiple layers. The present invention addresses these limitations by employing fluid transporting structures such as grooves or ridges located in the channel that laterally move the sheath fluid around the core fluid without requiring multi-level manufacturing or complex pumping systems.
Claims Coverage
The patent contains one independent method claim focusing on a sheath flow extrusion method that facilitates fully surrounding a core stream with a sheath stream within a channel using fluid transporting structures on opposing faces.
Sheath flow extrusion with fluid transporting structures on opposing channel surfaces
A method comprising providing a channel with opposed top and bottom surfaces having at least one fluid transporting structure on the top surface and at least one on the bottom surface, positioned facing one another across the channel between the proximal and distal ends. A sheath stream and a core stream are introduced side-by-side at the proximal end and flow down the channel. The fluid transporting structures transport the sheath stream laterally across the top and bottom surfaces to surround the core stream, controlling the core's size and shape, and extrude the core from the distal end.
Core stream comprising polymerizable, condensable, cross-linkable, or crystalizable material
The method includes the core stream containing materials that can be polymerized, condensed, cross-linked, or crystallized.
Multiple concentric layered streams via additional sheath streams
The method includes introducing at least a second sheath stream to create an output comprising multiple concentric layered streams.
The claims encompass a method of sheath flow extrusion employing fluid transporting structures on opposing channel surfaces to fully surround a core with sheath fluid, with capabilities to extrude polymerizable materials and form multiple concentric fluid layers.
Stated Advantages
The method can fully surround the core stream with sheath fluid, providing complete isolation from channel walls.
The sheath flow device operates over a broad range of channel sizes and viscosities, including high viscosity fluids and Reynolds numbers up to approximately 200.
The design can be readily incorporated into microfluidic chips without special manufacturing protocols, enabling simple fabrication with various techniques.
The relative flow rates of core and sheath streams can be widely varied without compromising sheath integrity, allowing real-time control of core diameter.
The device can reversibly unsheathe streams enabling efficient core and sheath fluid recapture, beneficial for resource-limited environments or precious core materials.
The system avoids constrictions and potential clogging points of nozzle-based designs, reducing back pressure and increasing reliability.
Documented Applications
Particle counting and flow cytometry, enabling focused cores completely sheathed to prevent fouling and enable accurate optical interrogation.
Fabrication of materials such as polymeric filaments and tubes with controlled and variable diameters, including tapered and shaped structures.
Liquid waveguides in microfluidic systems for guiding light in fluid streams based on refractive index differences.
Microdialysis without membranes, enabling diffusion-based separation of molecules between core and sheath streams with subsequent recapture.
Protection of conduits from fouling or corrosion by forming protective sheath layers around corrosive core fluids.
Reducing power requirements for transporting viscous fluids by sheathing high-viscosity core fluids in low-viscosity sheath fluids to reduce wall shear stress.
Continuous monitoring for biological warfare contaminants in air or water using a microfluidic flow cytometer with integrated sheath flow and optical interrogation.
Fabrication of complex multilayer structures including hollow tubes within hollow tubes by sequential sheath stream introduction.
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