Applied Physics Letters · 2002 · 296 citations · 16 references
EngineeringMaterials EngineeringMaterials ScienceBiosensorsMicroelectromechanical SystemsSensorsHydrogelsMems SensorsMicroelectromechanical SensorsMicroscale BiosensorsSensor MaterialsSoft SensorsCrosslinked HydrogelsCrosslinked PolymersMechanical AmplificationMicrocantilever SensorsMicrofabricated SensorsPolymer SwellingPolymer Swelling BehaviorSilicon-on-insulator Technology
We report on a pH sensor with ultrahigh sensitivity based on a microcantilever structure with a lithographically-defined crosslinked copolymeric hydrogel. Silicon-on-insulator wafers were used to fabricate cantilevers on which a polymer consisting of poly(methacrylic acid) (PMAA) with poly(ethylene glycol) dimethacrylate was patterned using free-radical UV polymerization. As the pH around the cantilever was increased above the pKa of PMAA, the polymer network expanded and resulted in a reversible change in surface stress causing the microcantilever to bend. Excellent mechanical amplification of polymer swelling as a function of pH change within the dynamic range was obtained, with a maximum deflection sensitivity of 1 nm/5×10−5 ΔpH.
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Smart single-chip gas sensor microsystem
Christoph Hagleitner, Andreas Hierlemann, D. Lange et al. · Nature · 2001 · 614 citations
Engineering, Chemical Engineering, Electrical Engineering +12