Advanced hydrogel-based chemical microsensors

The fascinating material class of stimuli-sensitive polymer hydrogels shows a distinct volume phase transition due to small changes in environmental parameters (chemical, physical, biological) of aqueous solutions. Thus, these hydrogels are ideal candidates for smart sensing layers and can be combined with arbitrary (micromachined) transducers to build chemical microsensors. This kind of sensors is highly advantageous due to low costs, the potential for miniaturization and mass production, their versatility with respect to the target analyte and their in-line capability. The implementation of these sensors in real-world applications requires long-term stable devices with a fast sensor response, which cannot be sufficiently fulfilled for most existing hydrogel-based sensors. Volume 50 of the book series Dresdner Beiträge zur Sensorik especially considers piezoresistive hydrogel-based sensors. Here, two approaches, to overcome the limitations of current sensors, are proposed. A material –based approach aims at the modification of the hydrogel material properties, i. e. the fabrication and integration of macroporous and clay-nanocomposite hydrogels. In a system-based approach, the force compensation method is applied where the responsive hydrogel structure is operated in a controlled feedback system. The theory, technology and implementation of both approaches are studied, such that they can be well adapted to hydrogel sensors using other transducer types.