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Article having closed microchannels

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Article having closed microchannels


An article includes at least one substrate including a solid composite material having metal nanoparticles dispersed in a polymer that provides a polymer matrix. At least one closed microchannel is formed in the substrate. The solid composite material provides a top wall for the closed microchannel. Surface contacts are on respective ends of the microchannel which allows fluids to be introduced into and removed therefrom, such as for use as a microfluidic device.

Browse recent University Of Central Florida Research Foundation, Inc. patents - Orlando, FL, US
Inventors: QUN HUO, HUI CHEN
USPTO Applicaton #: #20120276343 - Class: 428188 (USPTO) - 11/01/12 - Class 428 
Stock Material Or Miscellaneous Articles > Structurally Defined Web Or Sheet (e.g., Overall Dimension, Etc.) >Longitudinal Or Transverse Tubular Cavity Or Cell

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The Patent Description & Claims data below is from USPTO Patent Application 20120276343, Article having closed microchannels.

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CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. non-provisional patent application No. 11/774,796 entitled “LASER PROCESSING OF METAL NANOPARTICLE/POLYMER COMPOSITES” filed Jul. 9, 2007, now U.S. Pat. No. which claims priority to Provisional Application Ser. No. 61/613,807 entitled “LASER PROCESSING OF METAL NANOPARTICLE/POLYMER COMPOSITES” filed Jul. 7, 2006, which are both herein incorporated by reference in their entireties.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

The U.S. Government may have certain rights to the invention based on National Science Foundation Career Award DMR 0239424 and 0552295, and NIRT award DMI 0506531.

FIELD OF THE INVENTION

Disclosed embodiments relate to polymer-based articles having internal channels that can be used in the field of microfluidics.

BACKGROUND

Laser ablation polymeric materials are receiving increasing attention as substrates for microfluidic devices. Polymers possess a range of chemical, physical, and surface properties that allow great flexibility in matching materials to specific device applications. The cost of polymer substrates also can be significantly less than that of glass or silicon. In addition, fabrication of microchannels in polymer substrates is relatively simple and a greater variety of channel geometries, including complex 3-D systems, can be achieved in comparison to glass and silicon substrates.

There are many techniques employed for the fabrication of microchannels in polymer substrates including imprinting, etching, casting, and injection molding. While these methods are easily implemented, they require fabrication of a template, mask, or mold, otherwise known as a master. The creation of a master is time-consuming and adds an additional step to the microchannel fabrication process. Moreover, minor modifications to the design of a microchannel device require the fabrication of a completely new master.

To circumvent these problems, laser ablation of polymer substrates has been investigated as a method for forming microchannels for rapid proto-typing of different microfluidic geometries. Another potential feature of laser ablation is the capability of surface modification of channel walls concurrent with microchannel formation. However, conventional laser ablation is limited in the sense that it is incapable of forming closed microchannels, being only able to realize open channels and cavities.

SUMMARY

A method of forming articles having closed microchannels includes the steps of providing a substrate including a composite, the composite having metal nanoparticles dispersed in a polymer matrix (continuous phase), and generally are uniformly dispersed throughout a full volume of the polymer. The substrate is irradiated with a laser beam at an intensity and time sufficient to selectively remove the polymer below a surface of said substrate to form at least one microchannel, wherein the intensity and time is low enough to avoid removing the polymer above the microchannel, wherein an article having at least one closed microchannel is formed. The composite can be formed by dissolving a polymer in a solvent to form a solution, adding metal nanoparticles to the solution, and drying the solution to form the composite. The substrate and resulting article can be film. A preferred composite has gold nanoparticles dispersed in poly(methylmethacrylate). The method can be carried out while moving the substrate relative to the laser beam during the period of irradiation. A fluid can be passed over one or more surfaces of the substrate during the irradiation.

The method can be carried out on a coated substrate where the coating is a polymer or a second metal nanoparticle/polymer composite is placed on the substrate before irradiation with the laser. The coating can be the same polymer in the composite without any dispersed metal nanoparticles. Alternately some metal nanoparticles can be included in the coating defining a second metal nanoparticle/polymer composite where the concentration of the second metal particles in the coating is lower than the concentration of metal nanoparticles in the substrate. The second metal composite can have a different metal as compared to the metal in the substrate. The coating can be formed by depositing a solution of the coating material on the article and fixing the coating on the article by evaporation of the solvent. Deposition methods include casting, spraying or dipping.

The substrate can include a plurality of laminated layers where the individual layers can be polymer layers or metal nanoparticle/polymer composite layers. The polymers in the various polymer and composite layers can be the same polymer structure or can be different polymers. The metal nanoparticle/polymer composite layers can have the same or different metal nanoparticles and the concentration of the nanoparticles can be the same or different. In this way the different layers can be individually addressed by the laser to form microchannels in different layers by selectively activating nanoparticles in different layers of the laminate article.

In another embodiment, an article which can be used as a microfluidic device comprises at least one substrate, the substrate comprising a plurality of metal nanoparticles dispersed in a polymer comprising matrix. At least one closed microchannel is formed in the substrate. The metal nanoparticles can comprise gold and the polymer comprise poly(methylmethacrylate). The metal nanoparticles can comprise 0.2 to 10 weight percent of the substrate. The substrate can be a thin film. The substrate can comprise a plurality of substrates stacked on one another to form the article, wherein the metal nanoparticles vary in composition across the plurality of substrates.

BRIEF DESCRIPTION OF THE DRAWINGS

A fuller understanding of the present invention and the features and benefits thereof will be obtained upon review of the following detailed description together with the accompanying drawings, in which:

FIGS. 1(a)-(f) show scanned SEM images of gold nanoparticle-embedded poly(methyl methacrylate (PMMA) composite samples irradiated by a continuous wave Nd:YAG laser (532 nm) for 2 min, with the control sample image (no metal nanoparticles added to the polymer) shown in FIG. 1(a). With an increased concentration of nanoparticles in the composite film, the surface features progress from a bump to increasingly larger holes (FIG. 1(b)-(f).

FIGS. 2(a)-(d) show scanned SEM images of the irradiated films with laser power set at 30 mW. Sealed micro tunnels with a width around 300 μm are shown in FIG. 2(a). With excessive energy or duration of irradiation, the upper wall of the tunnels display ablation or cracking of the material (FIG. 2(b)). The smooth internal surface of a tunnel is shown for a tunnel after removal of the upper wall (FIG. 2(c)). A microchannel cut to expose a cross section shows that the micro tunnel is sealed (FIG. 2(d)).

FIGS. 3(a)-(c) show scanned SEM images of laser irradiated double layer films. The double layer films have a pure PMMA layer on top of a gold nanoparticle/PMMA composite layer.

FIG. 4 shows a cross sectional view of an article according to an embodiment of the invention comprising a plurality of closed microchannels formed in a composite substrate.



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stats Patent Info
Application #
US 20120276343 A1
Publish Date
11/01/2012
Document #
13539868
File Date
07/02/2012
USPTO Class
428188
Other USPTO Classes
International Class
32B3/26
Drawings
5



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