Design, Construction and Testing of a Monolithic pH Sensitive Hydrogel-Valve for Biochemical and Medical Application

VIRGINIA C. AYALA, MONIKA MICHALZIK, STEFFEN HARLING, HENNING MENZEL FABIO A. GUARNIERI AND STEPHANUS BÜTTGENBACH

Journal of Physics: Conference Series

Año: 2007 vol. 90 p. 1 - 11

In this work we report on a novel miniaturized pH-sensitive hydrogel-valve forimplementation in a microfluidic system. The control of fluid movement represents a criticalparameter in the design of these systems. To date, actuation methods for the delivery of samplefluids, such as electromagnetic, piezoelectric or thermopneumatic, require high powerconsumption. Using a microfluidic valve based on a stimuli-responsive material no externalpower source is necessary. For this reason smart materials like hydrogels that respond toexternal stimuli such as the pH-value are qualified. The presented valve was produced usingsoft-lithographic methods and consists of biocompatible materials. The actuator was fabricatedin-situ and the activation of the valve was produced by use of different pH-values. The firstinvestigations were made using a pH 1- and a pH 13-solution successively in order to test theactuator principle. Different times of exposure were used to polymerize the hydrogel and as aresult it was discovered that 16 minutes was the most adequate. These tests demonstrated theoperation of the hydrogel-valve and its applicability in a microfluidic device.Keywords—Hydrogels, biocompatibility, in-situ fabrication, soft-lithography, micro-valve,polydimethylsiloxane (PDMS)