Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1999-03-05
2003-01-07
Gallagher, John J. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S292000, C428S420000
Reexamination Certificate
active
06503359
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to methods and apparatuses for effecting adhesion, and particularly to methods and apparatuses for producing multi-laminate microfabricated, including microfluidic, devices.
BACKGROUND OF THE INVENTION
Recently, techniques first developed for the manufacture of microelectronic devices have been adapted to the manufacture of a wide variety of microfluidic devices for chemical analysis and synthesis.
For example, Wilding et al., U.S. Pat. No. 5,587,128, disclose devices particularly adapted for nucleic acid amplification, constructed by fabricating flow channels and one or more reaction chambers into the surface of a planar substrate; at least one of these engineered features has a cross-sectional diameter between 0.1 &mgr;m and 1,000 &mgr;m.
Zanzucchi et al., U.S. Pat. No. 5,593,838, disclose a microlaboratory disc variously adapted for performing nucleic acid assays or immunoassays, or for synthesizing peptides, oligonucleotides, or other combinatorially-constructed small molecules. The disc comprises a plurality of modular assay units, each comprising one or more arrays of sample wells 200-750 microns deep, interconnected by one or more channels at equivalent scale. Etching from both sides of the planar substrate permits the fabrication of a more complex network of overlapping capillary channels of similar dimensions, Zanzucchi et al., U.S. Pat. No. 5,681,484.
Heller et al., U.S. Pat. No. 5,605,662, describe microfluidic devices containing matrices of micron-sized locations, each of which is underlaid with a distinct and separately addressable microelectrode. The device is adapted to drive diagnostic and synthetic reactions, including nucleic acid hybridization and immunoassays.
Parce, U.S. Pat. No. 5,699,157, describes a microfluidic system for electrophoretic analysis of materials migrating in a microchannel fabricated in a planar substrate. The microchannels, fabricated by standard photolithographic or micromachining methods, such as laser drilling, range in diameter from about 0.1 &mgr;m to 100 &mgr;m.
WO 96/04547 (Lockheed Martin Energy Systems) describes a microchip laboratory system with micron-sized channels fabricated using standard photolithographic procedures and chemical wet etching, for use in capillary electrophoresis, DNA sequencing, gradient elution liquid chromatography, flow injection analysis, and chemical reaction and synthesis.
Chow et al., U.S. Pat. No. 5,800,690 describe microfluidic systems fabricated with a plurality of electrodes at nodes of a two-dimensional network of interconnecting capillary channels etched into a planar substrate; the electrodes create electric fields that move fluid-entrained materials electrokinetically through the channels.
Although the microfabrication techniques designed for semiconductor manufacture have proven useful in the precise fabrication of micron and sub-micron channels, wells, and other etched features in planar substrates, these techniques have not proven sufficient for completing the manufacture of many of these microfluidic systems. In particular, the techniques of photolithography, micromachining, vapor deposition and the like have proven ill-suited to the manufacture of microscopic features that are fluidly sealed.
Thus, to convert channels and wells into fluidly sealed capillaries and chambers, respectively, Wilding, U.S. Pat. No. 5,587,128, directs, without further explanation, that a cover be adhered or clamped to the planar substrate into which the engineered features have been etched. Chow et al., U.S. Pat. No. 5,800,690, and Parce, U.S. Pat. No. 5,699,157, analogously teach that a planar cover element be laid over the channeled substrate, and suggest generally that the planar cover element be attached to the substrate by thermal bonding, application of adhesives, or by natural adhesion between the two components.
But each of these proposed approaches—thermal bonding, application of adhesives, or natural (direct) adhesion—presents difficulties.
Although thermal bonding may be effective, sealing must be achieved at a temperature sufficiently low as to avoid distortion or destruction of the underlying substrate or substrate-embedded features. When the substrate and cover are silicon or glass, Zanzucchi et al., U.S. Pat. No. 5,593,838, teach that localized application of electric fields permits the meltable attachment of the cover element at about 700° C., well below the flow temperature of silicon (about 1400° C.) or of Corning 7059 glass (about 844° C.) WO 96/04547 (Lockheed Martin Energy Systems) teaches that a cover plate may be bonded directly to a glass substrate after treatment in dilute NH
4
OH/H
2
O
2
, followed by annealing at 500° C., well below the flow temperature of silicon-based substrates.
Recently, however, microfluidic laboratories have been proposed that may be constructed using plastic substrates. See, e.g., WO 97/21090 and WO 98/53311 (Gamera Bioscience); WO 96/09548 (Molecular Drives); EP A 0392475, EP A 0417305, and EP A 0504432 (Idemitsu). International applications published as WO 98/01533, WO 98/37238, and WO 98/38510, describe aspects of microfluidic platforms that are particularly adapted for detection by optical disk readers, such as CD and DVD readers; these assay disks are, accordingly, typically constructed using techniques and materials first developed in the optical disk arts. The plastics so used may melt or deform at temperatures far below those tolerated by silicon and glass.
There thus exists a need in the art for adhesion methods that permit lamination at temperatures sufficiently low as to prevent deformation or melting of plastic substrates. Furthermore, adhesion must be achieved at temperatures that prevent denaturation of biological macromolecules, such as antibodies, that may be disposed in and upon such substrates.
WO 98/45693 (Aclara Biosciences) discloses, inter alia, a thermal bonding method for fabricating enclosed microchannel structures in polymeric, particularly plastic, substrates. After apposing the planar surfaces of the two adherends, the temperature is maintained above the glass transition temperature of the polymer for a time sufficient to allow the polymer molecules to interpenetrate, and thus to bond, the two surfaces. Although the temperatures used are lower than those used in thermal bonding of semiconductors, the approach requires that the apposing planar surfaces of the base plate and cover be made of similar polymeric materials, and the temperatures may still be sufficient to cause deterioration of the optical properties at the interface. There thus still exists a need for a method of low temperature bonding that permits the adhesion of laminae of dissimilar polymeric materials without substantial optical distortion at the bonding interface.
Lamination using adhesives presents its own problems, principal among which is the potential for extrusion of adhesive from the bonding interface into the microfabricated channels and chambers formed between the laminae.
Beattie, U.S. Pat. No. 5,843,767, teaches that such extrusion may be prevented by the laser ablation of adhesive from selected areas of one of the adherends prior to adhesion. The prior ablation adds an additional fabrication step to the process, however, and serves to reduce the bonded surface area. WO 98/45693 (Aclara Biosciences) proposes to prevent extrusion by applying adhesive in a film no more than 2 &mgr;m thick, and in fluid curable embodiments further to control extrusion by rendering the adhesive nonflowable by partial curing before apposition of adherends. Each of these latter approaches requires careful attention to process.
There thus exists a need in the art for lamination methods that more readily prevent extrusion of adhesive from between adherent laminae and that may be used in a rapid process.
Bonding of laminae using adhesives presents other problems as well, many of which are exacerbated at microfabrication scale.
For example, physical application of such small volumes of adhesive may prove difficult, particularly w
Burstein Technologies, Inc.
Gallagher John J.
Oppenheimer Wolfe & Donnelly LLP
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