Cofabrication: A strategy for building multicomponent microsystems

Adam C. Siegel, Sindy K.Y. Tang, Christian A. Nijhuis, Michinao Hashimoto, Scott T. Phillips, Michael D. Dickey, George M. Whitesides

Research output: Contribution to journalArticle

45 Citations (Scopus)

Abstract

This Account describes a strategy for fabricating multicomponent microsystems in which the structures of essentially all of the components are formed in a single step of micromolding. This strategy, which we call "cofabrication", is an alternative to multilayer microfabrication, in which multiple layers of components are sequentially aligned ("registered") and deposited on a substrate by photolithography. Cofabrication has several characteristics that make it an especially useful approach for building multicomponent microsystems. It rapidly and inexpensively generates correctly aligned components (for example, wires, heaters, magnetic field generators, optical waveguides, and microfluidic channels) over very large surface areas. By avoiding registration, the technique does not impose on substrates the size limitations of common registrations tools, such as steppers and contact aligners. We have demonstrated multicomponent microsystems with surface areas exceeding 100 cm2, but in principle, device size is only limited by the requirements of generating the original master. In addition, cofabrication can serve as a low-cost strategy for building microsystems. The technique is amenable to a variety of laboratory settings and uses fabrication tools that are less expensive than those used for multistep microfabrication. Moreover, the process requires only small amounts of solvent and photoresist, a costly chemical required for photolithography; in cofabrication, photoresist is applied and developed only once to produce a master, which is then used to produce multiple copies of molds containing the microfluidic channels. From a broad perspective, cofabrication represents a new processing paradigm in which the exterior (or shell) of the desired structures are produced before the interior (or core). This approach, generating the insulation or packaging structure first and injecting materials that provide function in channels in liquid phase, makes it possible to design and build microsystems with component materials that cannot be easily manipulated conventionally (such as solid materials with low melting points, liquid metals, liquid crystals, fused salts, foams, emulsions, gases, polymers, biomaterials, and fragile organics). Moreover, materials can be altered, removed, or replaced after the manufacturing stage. For example, cofabrication allows one to build devices in which a liquid flows through the device during use, or is replaced after use. Metal wires can be melted and reset by heating (in principle, repairing a break). This method leads to certain kinds of structures, such as integrated metallic wires with large cross-sectional areas or optical waveguides aligned in the same plane as microfluidic channels, that would be difficult or impossible to make with techniques such as sputter deposition or evaporation. This Account outlines the strategy of cofabrication and describes several applications. Specifically, we highlight cofabricated systems that combine microfluidics with (i) electrical wires for microheaters, electromagnets, and organic electrodes, (ii) fluidic optical components, such as optical waveguides, lenses, and light sources, (iii) gels for biological cell cultures, and (iv) droplets for compartmentalized chemical reactions, such as protein crystallization.

Original languageEnglish (US)
Pages (from-to)518-528
Number of pages11
JournalAccounts of Chemical Research
Volume43
Issue number4
DOIs
StatePublished - Apr 20 2010

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Microsystems
Microfluidics
Optical waveguides
Wire
Microfabrication
Photolithography
Photoresists
Fused salts
Liquid Crystals
Electromagnets
Sputter deposition
Liquids
Molds
Fluidics
Biocompatible Materials
Substrates
Crystallization
Emulsions
Liquid metals
Cell culture

All Science Journal Classification (ASJC) codes

  • Chemistry(all)

Cite this

Siegel, A. C., Tang, S. K. Y., Nijhuis, C. A., Hashimoto, M., Phillips, S. T., Dickey, M. D., & Whitesides, G. M. (2010). Cofabrication: A strategy for building multicomponent microsystems. Accounts of Chemical Research, 43(4), 518-528. https://doi.org/10.1021/ar900178k
Siegel, Adam C. ; Tang, Sindy K.Y. ; Nijhuis, Christian A. ; Hashimoto, Michinao ; Phillips, Scott T. ; Dickey, Michael D. ; Whitesides, George M. / Cofabrication : A strategy for building multicomponent microsystems. In: Accounts of Chemical Research. 2010 ; Vol. 43, No. 4. pp. 518-528.
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Siegel, AC, Tang, SKY, Nijhuis, CA, Hashimoto, M, Phillips, ST, Dickey, MD & Whitesides, GM 2010, 'Cofabrication: A strategy for building multicomponent microsystems', Accounts of Chemical Research, vol. 43, no. 4, pp. 518-528. https://doi.org/10.1021/ar900178k

Cofabrication : A strategy for building multicomponent microsystems. / Siegel, Adam C.; Tang, Sindy K.Y.; Nijhuis, Christian A.; Hashimoto, Michinao; Phillips, Scott T.; Dickey, Michael D.; Whitesides, George M.

In: Accounts of Chemical Research, Vol. 43, No. 4, 20.04.2010, p. 518-528.

Research output: Contribution to journalArticle

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N2 - This Account describes a strategy for fabricating multicomponent microsystems in which the structures of essentially all of the components are formed in a single step of micromolding. This strategy, which we call "cofabrication", is an alternative to multilayer microfabrication, in which multiple layers of components are sequentially aligned ("registered") and deposited on a substrate by photolithography. Cofabrication has several characteristics that make it an especially useful approach for building multicomponent microsystems. It rapidly and inexpensively generates correctly aligned components (for example, wires, heaters, magnetic field generators, optical waveguides, and microfluidic channels) over very large surface areas. By avoiding registration, the technique does not impose on substrates the size limitations of common registrations tools, such as steppers and contact aligners. We have demonstrated multicomponent microsystems with surface areas exceeding 100 cm2, but in principle, device size is only limited by the requirements of generating the original master. In addition, cofabrication can serve as a low-cost strategy for building microsystems. The technique is amenable to a variety of laboratory settings and uses fabrication tools that are less expensive than those used for multistep microfabrication. Moreover, the process requires only small amounts of solvent and photoresist, a costly chemical required for photolithography; in cofabrication, photoresist is applied and developed only once to produce a master, which is then used to produce multiple copies of molds containing the microfluidic channels. From a broad perspective, cofabrication represents a new processing paradigm in which the exterior (or shell) of the desired structures are produced before the interior (or core). This approach, generating the insulation or packaging structure first and injecting materials that provide function in channels in liquid phase, makes it possible to design and build microsystems with component materials that cannot be easily manipulated conventionally (such as solid materials with low melting points, liquid metals, liquid crystals, fused salts, foams, emulsions, gases, polymers, biomaterials, and fragile organics). Moreover, materials can be altered, removed, or replaced after the manufacturing stage. For example, cofabrication allows one to build devices in which a liquid flows through the device during use, or is replaced after use. Metal wires can be melted and reset by heating (in principle, repairing a break). This method leads to certain kinds of structures, such as integrated metallic wires with large cross-sectional areas or optical waveguides aligned in the same plane as microfluidic channels, that would be difficult or impossible to make with techniques such as sputter deposition or evaporation. This Account outlines the strategy of cofabrication and describes several applications. Specifically, we highlight cofabricated systems that combine microfluidics with (i) electrical wires for microheaters, electromagnets, and organic electrodes, (ii) fluidic optical components, such as optical waveguides, lenses, and light sources, (iii) gels for biological cell cultures, and (iv) droplets for compartmentalized chemical reactions, such as protein crystallization.

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Siegel AC, Tang SKY, Nijhuis CA, Hashimoto M, Phillips ST, Dickey MD et al. Cofabrication: A strategy for building multicomponent microsystems. Accounts of Chemical Research. 2010 Apr 20;43(4):518-528. https://doi.org/10.1021/ar900178k