School of Mechanical Engineering Naftaly Krakover

24 בדצמבר 2018, 14:00 - 15:00 
בניין וולפסון חדר 206 
0
School of Mechanical Engineering Naftaly Krakover

 

 

School of Mechanical Engineering Seminar
Monday, December 24, 2018 at 14.00
Wolfson Building of Mechanical Engineering, Room 206

 

Frequency Based Micro Sensors

Naftaly Krakover

 Ph.D. student of Prof. Slava Krylov

Micro- and nanoelectromechanical systems (MEMS/NEMS)-based sensors are indispensable components in a large variety of products as diverse as consumer electronics, industrial, automotive and defense systems. Simplicity, manufacturability and integrability all contribute to an increasingly widespread use of these small-size low-cost devices. In the realm of high-end sensors, one of the promising and intensively researched approaches for performance improvement is based on the monitoring of the spectral characteristics of the devices. Resonant frequencies of the vibrating structure are extremely sensitive to the external stimuli such as acceleration or pressure and can be measured with high accuracy.

In this work, two different frequency-based sensing approaches ae introduced and their feasibility is demonstrated theoretically and experimentally. The first is a resonant displacement/acceleration sensor, which exploits electrostatic frequency tuning. The device incorporates a vibrating beam located in a close proximity to a quasi-statically deflecting body and interacting with it through the electrostatic field.  Perturbations of the field induced by the body’s deflection affect the effective stiffness of the beam and its natural frequency.  Sensitivity is enhanced by tailoring the nonlinear coupling force using fringing electrostatic fields. The feasibility of the suggested sensing scenario was demonstrated using the deflection measurement of a single crystal silicon micro scale pressurized membrane. The sensitivity of ≈ 30 Hz/kPa, which is equivalent to the displacement sensitivity of ≈ 4 Hz/nm, was registered in the experiments.

The second approach is related to the vibration-based structural health monitoring, especially in the low frequency range. One of the main challenges encountered by the MEMS vibration sensors developers is a large mismatch between typical frequencies of macro and micro scale structures.  Our approach is based on a purely mechanical realization of the superheterodyne principle, which allows conversion of low frequency input signals into high frequency response. The device benefits from the inertial coupling between the translational and tilting vibrational modes of a proof mass attached to an oscillating substrate. The translational vibration creates a time-harmonic offset between the mass and the tilting axis. The frequency mixing moment emerges as a product between the inertial force and the translational displacement. The structure is distinguished by its ability to combine both sensing and signal processing functions by the same device. Our model and experimental results collectively support the feasibility of the suggested concept. Extremely low power consumption of the device makes it especially suitable for autonomous distributed sensors networks valuable for future Internet of Things (IoT) applications.

אוניברסיטת תל אביב עושה כל מאמץ לכבד זכויות יוצרים. אם בבעלותך זכויות יוצרים בתכנים שנמצאים פה ו/או השימוש
שנעשה בתכנים אלה לדעתך מפר זכויות, נא לפנות בהקדם לכתובת שכאן >>