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Issue 7, 2007
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Stop-flow lithography in a microfluidic device

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Abstract

Polymeric particles in custom designed geometries and with tunable chemical anisotropy are expected to enable a variety of new technologies in diverse areas such as photonics, diagnostics and functional materials. We present a simple, high throughput and high resolution microfluidic method to synthesize such polymeric particles. Building off earlier work that we have done on continuous flow lithography (CFL) (D. Dendukuri, D. C. Pregibon, J. Collins, T. A. Hatton, P. S. Doyle, Nat. Mater., 2006, 5, 365–369; ref. 1), we have devised and implemented a new setup that uses compressed air driven flows in preference to syringe pumps to synthesize particles using a technique that we call stop-flow lithography (SFL). A flowing stream of oligomer is stopped before polymerizing an array of particles into it, providing for much improved resolution over particles synthesized in flow. The formed particles are then flushed out at high flow rates before the cycle of stop-polymerize-flow is repeated. The high flow rates enable orders-of-magnitude improvements in particle throughput over CFL. However, the deformation of the PDMS elastomer due to the imposed pressure restricts how quickly the flow can be stopped before each polymerization event. We have developed a simple model that captures the dependence of the time required to stop the flow on geometric parameters such as the height, length and width of the microchannel, as well as on the externally imposed pressure. Further, we show that SFL proves to be superior to CFL even for the synthesis of chemically anisotropic particles with sharp interfaces between distinct sections.

Graphical abstract: Stop-flow lithography in a microfluidic device

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Publication details

The article was received on 13 Mar 2007, accepted on 01 May 2007, published on 21 May 2007 and first published online on 21 May 2007


Article type: Paper
DOI: 10.1039/B703457A
Citation: Lab Chip, 2007,7, 818-828
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    Stop-flow lithography in a microfluidic device

    D. Dendukuri, S. S. Gu, D. C. Pregibon, T. A. Hatton and P. S. Doyle, Lab Chip, 2007, 7, 818
    DOI: 10.1039/B703457A

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