Microelectromechanical systems (MEMS) have been developed into numerous physical sensors. While individual sensors have demonstrated the viability of the technology, many applications require arrays of many different sensors. Development of efficient methods to monitor resonant sensor arrays is proposed including the integration of the monitoring system with micromechanical sensor arrays.
Microsystems for monitoring temperature, pressure, acceleration, rotation, stress, chemicals, biological agents and other physical parameters have been developed. Often information for more than one parameter or single parameters at numerous locations is required. A method to probe numerous sensors simultaneously will be developed. The method is based on energy absorption of resonant sensing circuits. Energy absorption techniques are well known in spectroscopy but have not been applied to sensor arrays. Rather than look at the energy emission and absorption of atomic transitions in materials, energy absorption of sensing arrays will be investigated using similar techniques.
The sensor that will initially be integrated into the sensing system will be the flexural plate resonator. This sensor was chosen because it has been demonstrated for both chemical and biological agents, operates in liquid and vapor environments, has resonant frequencies in the megahertz range and can be easily microfabricated using standard techniques. The resonant sensor will be manufactured to have a resonant frequency that is within the electrical absorption frequencies of an inductor-capacitor circuit. Electrical energy will inductively couple into the electrical circuit and drive the sensor into resonance. The absorption of the electrical and mechanical energy will effectively change the impedance of the driving circuit, the maximum change being at the mechanical resonance of the sensor. The resonant frequency will vary with changes in the mass and stresses of the structure. This is made sensitive to different agents by coating the resonant surface with thin film sorption layers. Combining numerous sensors will create an absorption spectrum that can be used to monitor resonances by FM spectroscopy techniques. The system will sweep the frequency and lock to each resonance, record the value then continue the sweep to the next resonance, much like the scan button on car radios.
The intellectual merit of this research is the development of wireless sensor interrogation technology and the application of these technologies to interdisciplinary problems that require sensors. The goal of this research is to develop a wireless telemetry system for remotely interrogating arrays of resonant MEMS sensors based on the absorption of electrical energy through inductive coupling. These sensors and sensing system would have applications as chemical vapor and biochemical detectors, as well as strain, humidity, pressure and acceleration sensors.
The broader impact of this research is the continued integration of sensor technology with microelectromechanical systems and radio frequency identification. This work will lay the foundation to create a system that will passively monitor parameters, store the information through electrical or mechanical means and transmit the data when probed. This research will increase the investigators knowledge base and expertise in system performance assessment, and this research will also impact the education of both graduate and undergraduate students through the respective university curriculum and student research programs. The multi-disciplinary features of this research will require graduate students of mechanical, electrical and chemical engineering to interact to solve the stated problem.
