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Pressure-Sensitive Microvalves Made from Polymer Brushes

Published online by Cambridge University Press:  16 February 2011

E.M. Sevick  and
D.R.M. Williams
E.M. Sevick
Affiliation:
Department of Chemical Engineering, University of Colorado, Boulder, CO 80309-0424
D.R.M. Williams
Affiliation:
Institute of Advanced Studies, Research School of Physical Sciences and Engineering, The Australian National University, Canberra, and Institute for Theoretical Physics, University of California at Santa Barbara, CA, 93106 and Department of Physics, University of Michigan, Ann Arbor MI 48109-1120
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Abstract

We describe a novel microvalve, constructed from polymer chains end-grafted onto opposing surfaces of a narrow slit. The assembly of polymer chains acts as both sensor and valve for microflow control and bypasses the need to construct an external feedback mechanism. This microflow control results from densely grafted chains which repel one another and stretch away from the surface, forming a brush which acts as an elastic and impenetrable layer. The height of a sheared brush increases or decreases depending upon solvent quality, i.e the layer can show a negative Poission's ratio. The discharge through the brushlined conduit is a non-linear function of pressure enabling different modes of valve operation. For brushes which extend moderately into the inter-slit region the valve assembly maintains constant discharge over a wide range of pressure. For brushes which extend far into the inter-slit region the valve assembly cuts off flow above a critical pressure, limiting the maximum discharge.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 360 , 1994 , 329
Copyright
Copyright © Materials Research Society 1995

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