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Microfluidic systems including three-dimensionally arrayed channel networks

a microfluidic system and channel network technology, applied in microstructural devices, microstructured technology, liquid/fluent solid measurement, etc., can solve the problems of complex channels with more complex connectivity than can be generated, difficult to perform, and high cos

Inactive Publication Date: 2008-05-29
PRESIDENT & FELLOWS OF HARVARD COLLEGE
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention relates to improved microfluidic systems and methods for fabricating them. The invention provides a convenient route to topologically complex and improved microfluidic systems, which can incorporate multiple materials onto surfaces without the need for multiple steps of registration or stamping during patterning. The invention also provides microfluidic systems that can pattern onto surfaces biological materials and cells without the need for separate steps of contacting and hardening a liquid. The invention also includes a polymeric membrane with a microfluidic network structure that can pattern onto surfaces with at least one two-level topological feature having at least one cross-sectional dimension not exceeding about 500 μm. Overall, the invention provides improved methods for fabricating microfluidic systems with complex patterns and materials, which can be useful in various fields such as biological research and medical applications.

Problems solved by technology

The need for complexity in microfluidic systems is increasing rapidly as sophisticated functions—chemical reactions and analyses, bioassays, high-throughput screens, and sensors—are being integrated into single microfluidic devices.
Complex systems of channels require more complex connectivity than can be generated in conventional two-dimensional microfluidic systems having a single level of channels, since such typical single-level designs do not allow two channels to cross without fluidically connecting.
315-332, 1998), that yield three-dimensional structures, but these methods are typically time consuming, difficult to perform, and expensive, and are thus not well suited for either prototyping or manufacturing, and are also not capable of making certain types of structures.

Method used

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  • Microfluidic systems including three-dimensionally arrayed channel networks
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  • Microfluidic systems including three-dimensionally arrayed channel networks

Examples

Experimental program
Comparison scheme
Effect test

example 1

Fabrication of a Mold Master by Multi-Level Photolithography

[0179]A mold master of photoresist on silicon having two levels of features in positive, high relief (i.e., protruding above the surface of the silicon wafer) was fabricated using the two-level photolithography technique outlined in FIG. 8. Designs for the channel systems for the first and second levels were generated with a CAD computer program (Free-Hand 8.0, MacroMedia, San Francisco, Calif.). High resolution (3386 dpi) transparencies were made by printing with a commercial printer (Linotype, Hercules Computer Technology, Inc., Freemont, Calif.) from the CAD computer files. Two transparencies were produced, the first comprising the photomask for producing features in the first level of the mold master and the second comprising photomask for producing the features in the second level of the mold master.

[0180]Negative photoresist (SU8-50, Microlithography Chemical Corp., Newton, Mass.) was spin-coated (at about 5,000 rpm f...

example 2

Fabrication of a Three-Dimensional Microfluidic Network Including a System of Channels in a “Basketweave” Configuration

[0183]In the following example, the method outlined in FIGS. 9a and 9b was utilized to produce a microfluidic network structure including a channel pattern therein having a basketweave structure similar to that illustrated in FIG. 1a. First, a bottom master was produced as described above in Example 1 having disposed thereon two-level topological features for forming channels within the molded replica arranged similarly to those shown schematically in FIG. 12a by bottom master 1000. The second step of the process comprised formation of a top master including features for forming channels in the uppermost level of the replica molded membrane. A similar schematic arrangement of features for producing the channels, and the way in which the channels of the upper mold master and lower mold master fit together to mold the overall structure, is also illustrated in FIG. 12a...

example 3

Fabrication of Microstructures by Replica Molding with a Microfluidic Network Structure

[0190]A microfluidic membrane including a three-level channel system in a basketweave pattern was produced as described in Example 2. The microfluidic membrane was placed upon a flat PDMS slab so that the upper surface of the PDMS slab and the lower surface of the membrane were in conformal contact but were not irreversibly sealed to each other. The upper surface of the membrane was left open to the atmosphere. An epoxy prepolymer (EP-TEK, Epoxy Technology, Billerica, Mass.) was then placed at the channel openings and allowed to fill the channel structure by capillary action. After approximately 1 hour standing at ambient pressure, the epoxy had degassed and filled the channels completely. The filled channels were then exposed to UV light (as described above in Example 1) for about 20 min through the PDMS. The surrounding PDMS microfluidic membrane was then dissolved in tetrabutylammonium fluoride...

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Abstract

The present invention provides, in certain embodiments, improved microfluidic systems and methods for fabricating improved microfluidic systems, which contain one or more levels of microfluidic channels. The inventive methods can provide a convenient route to topologically complex and improved microfluidic systems. The microfluidic systems provided according to the invention can include three-dimensionally arrayed networks of fluid flow paths therein including channels that cross over or under other channels of the network without physical intersection at the points of cross over. The microfluidic networks of the invention can be fabricated via replica molding processes, also provided by the invention, utilizing mold masters including surfaces having topological features formed by photolithography. The microfluidic networks of the invention are, in some cases, comprised of a single replica molded layer, and, in other cases, are comprised of two, three, or more replica molded layers that have been assembled to form the overall microfluidic network structure. The present invention also describes various novel applications for using the microfluidic network structures provided by the invention.

Description

RELATED APPLICATIONS[0001]This application is a divisional of U.S. application Ser. No. 10 / 303,642, filed Nov. 25, 2002 which is a continuation of PCT International Application No. PCT / US01 / 16973 filed May 25, 2001, which is a continuation-in-part of U.S. application Ser. No. 09 / 578,589, filed May 25, 2000. Each application is hereby incorporated by reference in its entirety.FIELD OF INVENTION[0002]The present invention involves microfluidic network structures, methods for fabricating microfluidic network structures, and methods for using such structures.BACKGROUND OF THE INVENTION[0003]The need for complexity in microfluidic systems is increasing rapidly as sophisticated functions—chemical reactions and analyses, bioassays, high-throughput screens, and sensors—are being integrated into single microfluidic devices. Complex systems of channels require more complex connectivity than can be generated in conventional two-dimensional microfluidic systems having a single level of channels...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): G03F7/38B01D61/18B01D67/00B01D69/02B01D71/70B01L3/00B01L99/00B81B1/00
CPCB01D61/18Y10T436/11B01D69/02B01D71/70B01L3/502707B01L2300/0874B01L2300/0887B29C33/3857B29C33/3892B29C33/52B29C35/0888B29C39/021B29C39/34B29C2035/0827B81B2201/058B81C1/00119B81C2201/019B01D67/0034B01D2323/24B01D2323/34B01D2325/028B01D2325/08Y10T436/2575B01D67/003B33Y80/00B01D71/701
Inventor ANDERSON, JANELLE R.CHIU, DANIEL T.JACKMAN, REBECCA J.CHERNIAVSKAYA, OKSANAMCDONALD, J. COOPERWHITESIDES, GEORGE M.
Owner PRESIDENT & FELLOWS OF HARVARD COLLEGE
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