Chemical detectionNew technology will allow miniaturization of chemical sensors
A new measuring technology – based on measuring near-resonant nonlinear behaviors rather than measuring chemomechanically induced shifts in linear natural frequency – will allow a dramatic miniaturization of sensors; the miniaturization will make these sensors more suitable for first response, law enforcement, and military missions
Over the past two decades, the potential to detect very small amounts of added mass has driven research in chemical and biological sensors based on resonant micro- and nanoelectromechanical systems.
Traditional resonant mass sensors utilize chemomechanically induced shifts in linear natural frequency for mass detection, but alternative sensing approaches, those which exploit near-resonant nonlinear behaviors, have been the focus of interest of the research community because of their potential to yield improved sensor metrics and to simplify final device implementations.
A just-published paper examines the development of an amplitude-based mass sensing approach which uses the dynamic transitions that occur near a cyclic-fold/saddle-node bifurcation in the nonlinear frequency response of a piezoelectrically actuated microcantilever. In less technical terms, the sensors’ microcantilevers — slivers of silicon shaped like small diving boards — vibrate at their natural, or “resonant,” frequency. By analyzing the frequency change when a particle lands on the microcantilever, scientists can reveal the particle’s presence and potentially its mass and composition.
A Purdue University release notes that measuring amplitude is far easier than measuring frequency because the amplitude changes dramatically when a particle lands on the microcantilever, whereas the change in frequency is minute.
Jeffrey Rhoads, an assistant professor of mechanical engineering at Purdue, notes that the main advantage of the new measuring technology is that it will allow a dramatic miniaturization of sensors. The miniaturization will make these sensors more suitable for first response, law enforcement, and military missions.
“When you try to shrink [sensors], the old way of measuring does not work as well,” Rhoads said. “We’ve made the signal processing part easier, enabling small-scale, lower-power sensors, which are more reliable and have the potential for higher sensitivities.”
The paper details the modeling, analysis, and experimental validation of this mass sensing technique.
The experimental results presented in the paper not only prove the feasibility of the proposed sensing approach, but also allow for the direct evaluation of pertinent sensor metrics.
— Read more in V. Kumar et al., “Modeling, Analysis, and Experimental Validation of a Bifurcation-Based Microsensor,” Microelectromechanical Systems (3 February 2012) (DOI: 10.1109/JMEMS.2011.2182502)
