סמינר מחלקה של יואב קסלר - "מד זרימה תרמו-מכאני זעיר"
School of Mechanical Engineering Seminar
Monday, February 28, 2022 at 14.00
Wolfson Building of Mechanical Engineering, Room 206
Active MEMS Flow Sensor
Ph.D. student of Prof. Slava Krylov and Alex Liberzon
In this work, we suggest a new flow sensing paradigm, which exploits the intrinsic coupling
between the flow and between the electrothermal and mechanical nonlinear behavior of bistable beams. In addition to the theoretically infinite sensitivity, sensors reported in this work allow measuring two components of the flow in a single location, or the velocity at two close locations in the flow filed, resulting in a velocity gradient measurement, using a single sensing element. The ability to measure multiple points in the flow field using a single element introduces new and alluring abilities in fluid flow measurements. The suggested approach could help to replace the intricate fabrication and assembly process of the state-of-the-art sensor arrays for gradient flow measurements, with a straightforward fabrication and integration. The proposed sensing method allows versatile modes of operation, measuring a single point or multiple points in the flow, and control over the inherent trade off between enhanced sensitive and power consumption or the range of measured velocities.
We explore the opportunity to utilize the hysteresis nature of the bistable mechanism for flow velocity measurement at two different closely located points using a single sensing element. An electrostatically actuated initially curved bistable microbeam heated by an electric current and convectively cooled by airflow is switched between two stable locations through the snap-through (ST) and snap-back (SB) buckling mechanisms. The velocities of an air flow at these positions are obtained by measuring the critical ST and SB values of the actuation voltage. In the experiments, our 500 m long, 2 m wide single-crystal Si beam with 2.5m nominal initial elevation demonstrated sensitivity of SST 0.25 V/(m/s) and SSB 0.84 V/(m/s) at the ST and SB points, respectively. In the present device, the distance between the two measurement points is 10 m. Our experimental results indicate that the suggested approach can be used for the velocity gradient measurements. The sensing principle relying on a single bistable sensing element opens new opportunities for measurement of gas flow velocity and velocity gradients at scales significantly smaller than the state-of-the-art multi hot-wire sensors.