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Issue 16, 2012
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Pinned films and capillary hysteresis in microfluidic channels

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Abstract

Pinned water films in a microfluidic channel act as elastic membranes under tension that increase capillary pressures while preserving the mechanical work dissipated around capillary pressure-saturation, PcSw, hysteresis cycles. High-resolution two-photon laser micromachining of SU-8 photoresist was used to fabricate wedge-shaped microfluidic channels that included sharp edge features to pin wetting films during drainage. The films were measured using confocal fluorescence microscopy. The tension in the film acts as an elastic tether that shifts the PcSw hysteresis cycle higher in pressure relative to the hysteresis cycle in the same sample when films are not pinned. The film tension is strongly nonlinear as the restoring force decreases with increasing displacement. The contribution of elastic forces to hysteresis has important consequences for pressure and saturation control in microfluidics.

Graphical abstract: Pinned films and capillary hysteresis in microfluidic channels

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Article information


Submitted
11 Mar 2012
Accepted
20 Apr 2012
First published
24 Apr 2012

Lab Chip, 2012,12, 2858-2864
Article type
Paper

Pinned films and capillary hysteresis in microfluidic channels

Y. Liu, D. D. Nolte and L. J. Pyrak-Nolte, Lab Chip, 2012, 12, 2858
DOI: 10.1039/C2LC40247E

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