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Issue 4, 2010
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A microchip fabricated with a vapor-diffusion self-assembled-monolayer method to transport droplets across superhydrophobic to hydrophilic surfaces

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Abstract

A wettability gradient to transport a droplet across superhydrophobic to hydrophilic surfaces is fabricated on combining a structure gradient and a self-assembled-monolayer (SAM) gradient. The combination of these two gradients is realized with a simple but versatile SAM technique, in which the textured silicon wafer strip is placed vertically in a bottle that contains a decyltrichlorosilane solution to form concurrently a saturated SAM below the liquid surface and a wettability gradient above. The platform fabricated in this way has a water-contact angle from 151.2° to 39.7°; the self-transport distance is hence increased significantly to about 9 mm. A theoretical model that approximates the shape of a moving drop to a spheroidal cap is developed to predict the self-transport behavior. Satisfactory agreement is shown for most regions except where the hysteresis effect is unmeasurable and an unsymmetrical deformation occurs. A double-directional gradient surface to alter the direction of movement of a droplet is also realized. The platforms we developed serve not only to transport a fluid over a long distance but also for a broad spectrum of biomedical applications such as protein adsorption, cell adhesion and DNA-based biosensors.

Graphical abstract: A microchip fabricated with a vapor-diffusion self-assembled-monolayer method to transport droplets across superhydrophobic to hydrophilic surfaces

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Publication details

The article was received on 26 Aug 2009, accepted on 28 Oct 2009 and first published on 01 Dec 2009


Article type: Paper
DOI: 10.1039/B917624A
Lab Chip, 2010,10, 499-504

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    A microchip fabricated with a vapor-diffusion self-assembled-monolayer method to transport droplets across superhydrophobic to hydrophilic surfaces

    Y. Lai, J. Yang and D. Shieh, Lab Chip, 2010, 10, 499
    DOI: 10.1039/B917624A

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