Optimization and Capacitive Interface Design for a Resonant MEMS Embedded Chemical Sensing System
Author(s)
Guo, Hongyu
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Abstract
There is a clear need in multiple industries for a cost-effective and portable sensor that is both selective and sensitive. The primary objective of this thesis is to optimize the design of a battery-powered embedded system that utilizes a MEMS-based (microelectromechanical systems) resonant sensor to detect volatile organic compounds (VOCs), enabling real-time data collection and processing in the field while being small enough to be wearable. This new, portable, system is compared to the benchtop closed loop system previously used in the iSenSys lab, and its advantages are discussed.
Extensive testing and characterization were first conducted on a previously designed portable automatic gain control (AGC) system in the lab. After this characterization was complete, a new iteration of the system with additional software and features was designed and tested with multiple VOCs. The data collected from these tests are compared to the benchtop closed loop system to confirm that the new design operates as expected while remaining portable. All of the features were verified and added to a new version of the board.
The iSenSys MEMS sensor also has electrodes on its surface to perform capacitance sensing, but no portable interface for this yet exists. Measuring capacitance would provide a dataset independent of frequency to help identify analytes, improving the selectivity of the device. Part of this project aims to accomplish this by developing an effective and portable interface using a commercial capacitance to digital converter. A prototype was constructed using an Arduino to test the viability of this interface and the performance and sensitivity of capacitance sensing on an embedded system is quantified and analyzed.
Moving forward, a new board that combines the closed loop frequency sensing with the new features and capacitive sensing interface was designed, fabricated, and assembled. This system includes multiplexors, allowing it to collect data from four devices on each sensor die instead of only being connected to one device like the previous boards. Preliminary testing for basic operation has been completed on this board, but further testing with multiple gases is still in progress.
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Date
2025-08-18
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Thesis (Masters Degree)