Sheath flow methods for fabricating structures
Inventors
Mott, David R. • Howell, JR., Peter B. • Ligler, Frances S. • Fertig, Stephanie • Bobrowski, Aron
Assignees
Publication Number
US-10099417-B2
Publication Date
2018-10-16
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 having at least one fluid transporting structure located on the top and bottom surfaces of the channel. These structures transport sheath fluid laterally across the channel to fully surround a core fluid stream. At the channel's introduction point, the sheath fluid and core solution flow side by side or the core may be bounded on both sides by sheath fluid. This design allows the core fluid to be encircled by the sheath fluid inside the channel, maintaining its interior position through laminar flow.
The problem addressed arises from previous sheath flow designs which were either limited to two-dimensional sheath flow, required complex multi-level microfabrication, or necessitated separate pumps for multiple sheath streams increasing manufacturing and usage complexity. Traditional annular designs required precise alignment and fixed core sizes, while microfluidic chip designs only sheathed the core stream laterally, leaving top and bottom contact with channel walls, risking fouling and complicating optical detection. These limitations hindered easy manufacture, flexibility in flow control, and reliable focusing of the core stream for applications such as flow cytometry, particle counting, and material fabrication.
The invention overcomes these problems by using fluid transporting structures such as grooves or ridges in the channel to direct the sheath stream completely around the core stream within a single microfluidic channel, thereby fully separating the core solution from the walls. The channel design is adaptable across a broad size range, functional with high or low viscosity fluids, and can be fabricated using common microfabrication techniques without complex stacking or multiple pumps. The system allows real-time variation of core size without nozzle constrictions, enabling diverse applications including extruding materials, fabricating structures, microdialysis without membranes, and liquid waveguides.
Claims Coverage
The patent claims 2 claims including 1 independent method claim and 1 dependent method claim related to fabricating structures using a sheath flow device.
Sheath flow channel with fluid transporting structures on top and bottom surfaces
A channel having opposed top and bottom surfaces with at least one fluid transporting structure across the channel on each surface, positioned between the proximal and distal ends and facing one another across the channel.
Encircling core stream with sheath stream using fluid transporting structures
Introducing a sheath stream and a core stream at the channel's proximal end flowing side-by-side towards the distal end, whereby the fluid transporting structures transport the sheath stream across both top and bottom surfaces to fully surround the core stream.
Core stream comprising material capable of forming a structure
The core stream includes material that is capable of forming a structure, facilitating fabrication using the sheath flow arrangement.
Creating multiple concentric layered streams by additional sheath streams
Introducing at least a second sheath stream to create an output of multiple concentric layered streams.
The claims cover a sheath flow method and device having fluid transporting structures on opposite surfaces of a channel that transport sheath fluid to fully surround a core stream composed of structurable material, including configurations that produce multiple concentric layered streams, enabling fabrication via this controlled sheath flow.
Stated Advantages
The design can be readily fabricated using various conventional techniques without special manufacturing protocols or complex multi-level construction.
The system functions over a broad range of channel sizes and is suitable for high or low viscosity fluids.
The sheathing effect reliably isolates the core fluid from channel walls, preventing fouling and allowing precise focusing of the core stream.
Relative flow rates of core and sheath streams can be widely varied in real time to adjust core size without requiring nozzle size changes, reducing clogging risk and backpressure.
The sheath flow device enables reversible sheathing, allowing recapture and reuse of both core and sheath fluids.
The device operates passively, is inexpensive, and can be readily produced for parallel operation in arrays for high throughput.
Documented Applications
Particle counting and flow cytometry, including miniaturized microfluidic flow cytometers with sheathed core streams for biological sample analysis.
Extrusion and fabrication of materials such as polymeric filaments and tubes with controllable diameter and shape, including structures with varying cross-sectional geometry and gradients.
Microdialysis without membranes via diffusion between sheath and core streams, allowing removal of small molecules while retaining larger particles or cells.
Coating and protection of conduits or channels from fouling or corrosion by forming protective sheath layers.
Reducing power requirements for pumping viscous fluids by sheathing high viscosity core fluids in lower viscosity sheath fluids.
Liquid waveguides for optical applications where light is guided in the core or sheath stream for chemical or biological measurements.
Nearfield optical microscopy using tapered core stream waveguides produce optical probes entirely out of liquid.
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