H. Schlicke, S.C. Bittinger, H. Hartmann, T. Vossmeyer
Fraunhofer Center for Applied Nanotechnology,
Germany
Keywords: gas sensors, MEMS, NEMS, gold nanoparticles, membranes, thin films, multivariate sensing, chemiresistors
Summary:
In this contribution we present a novel transduction method, employing the microelectromechanical response of nanocomposite membranes, consisting of organically cross-linked gold nanoparticles, as chemical sensing signal. GNP membranes were transferred onto suitable microstructures equipped with electrodes. By application of AC or DC voltages between the membranes and counter electrodes quasi-static deflections or resonant oscillations were induced, respectively. We observed a significant impact of analyte sorption on these microelectromechanical responses, i.e., changes of the deflection amplitudes and resonance frequencies, presumably due to sorption-induced variations of the membranes’ pre-stress. Employing frequency shifts of GNP membrane based resonators exposed to e.g. toluene vapor as sensing signal, even concentrations in the low ppm range could easily be detected. We further present our current research targeting the formation of multivariate sensing platforms based on freestanding GNP membranes, employing both, chemiresistive as well as microelectromechanical transduction. Due to the different transduction mechanisms, both approaches show different selectivities. Additionally, we observed that the response kinetics of GNP membrane based microelectromechanical chemical sensors strongly depend on the size/structure of the analyte molecule. By combining the different transduction mechanisms with interpretations of the response kinetics, we demonstrate successful discrimination between analytes.