Diffusion of water into SU-8 microcantilevers

We present a method to monitor the diffusion of liquid molecules in polymers. A microdrop of water is deposited by a piezoelectric drop generator onto the upper surface of a cantilever made of SU-8 based photoresist. In response, the cantilever bends in the opposite direction. We find that this bend...

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Bibliographic Details
Published in:Physical chemistry chemical physics : PCCP 2010-01, Vol.12 (35), p.1577-1583
Main Authors: Liu, Chuanjun, Liu, Ying, Sokuler, Mordechai, Fell, Daniela, Keller, Stephan, Boisen, Anja, Butt, Hans-Jürgen, Auernhammer, Günter K, Bonaccurso, Elmar
Format: Article
Language:English
Subjects:
Bending
Bends
Chemistry
Diffusion
Exact sciences and technology
General and physical chemistry
Liquids
Mathematical models
Monitors
Photoresists
Swelling
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Summary:We present a method to monitor the diffusion of liquid molecules in polymers. A microdrop of water is deposited by a piezoelectric drop generator onto the upper surface of a cantilever made of SU-8 based photoresist. In response, the cantilever bends in the opposite direction. We find that this bending is mainly caused by the diffusion of water into the cantilever and the consequent swelling of SU-8. Using a one-dimensional diffusion model and assuming a simple swelling law, we qualitatively model the bending of the cantilever during in and out diffusion of water in SU-8. With a more sophisticated finite element model the diffusion coefficient of water in the SU-8polymer can be determined quantitatively from the dynamics of cantilever bending. By measuring the bending of polymer cantilevers and modeling the process by finite elements we could determine the diffusion coefficient of, e.g. , water molecules in the photoresist SU-8.
ISSN:1463-9076
1463-9084
DOI:10.1039/c002478c