Research Highlights: Bifurcation-Based & Resonant MEMS Flow Sensors

Overview

Our laboratory specializes in developing novel Micro-Electro-Mechanical Systems (MEMS) for airflow sensing. Unlike conventional sensors that rely on linear deflection, our research exploits nonlinear structural dynamics - specifically, bistability, snap-through buckling, and parametric resonance - to achieve high sensitivity, broad tunability, and robust detection limits.

By combining electro-thermal actuation with complex fluid-structure interactions, we are defining the next generation of flow sensors.

Key Research Areas

1. Bistable "Snap-Through" Sensors

We utilize the phenomenon of bistability—where a curved micro-beam snaps between two stable positions—as a sensing mechanism. This "digital" response offers distinct advantages in detecting flow thresholds.

• Piezoresistive Detection: Moving away from bulky optical setups, we have successfully integrated piezoresistive layers on bistable beams. This allows for fully on-chip electrical detection of the snap-through event induced by airflow.

• Sampling Rate Limits: We have rigorously analyzed the theoretical and practical limits on the cycle rate of these bistable sensors, establishing guidelines for their use in high-frequency turbulent-flow measurements.

• Mechanism: The sensors use curved microbeams that buckle under flow pressure or thermal loads, producing a sharp, clear signal when a specified velocity threshold is exceeded.

2. Resonant & Tunable Sensing

Our most recent work focuses on frequency modulation rather than static displacement.

• High Tunability: By monitoring the resonant frequency of electro-thermally heated beams, we have developed sensors that can be "tuned" to different sensitivity ranges. This enables a single sensor to operate effectively across a wide range of airflow velocities.

• Parametric Excitation: We utilize Joule heating not only for static actuation but also to parametrically excite the microbeams, creating a highly sensitive resonant system that interacts dynamically with the surrounding fluid.

3. Thermo-Fluid-Structure Interaction

A core component of our modeling involves the complex coupling between heat, structure, and fluid flow.

• Overheat & Direct Flow: We investigate how Joule heating (overheat) interacts with direct flow loading. Understanding this relationship is crucial for preventing sensor burnout and ensuring accurate readings when the sensor is used as a hybrid hot-wire/hot-film anemometer.

• Actuation Physics: Our research details how electro-thermal actuation alters the buckling response in parallel and transverse flows, providing the fundamental physics required to design robust sensors.

Selected Publications

• Highly tunable airflow velocity MEMS sensor based on resonant frequency monitoring Litvinov, I., Drizovsky, M., Milo, G. S., Liberzon, A., & Krylov, S.Measurement (2025).

• Piezoresistive snap-through detection for bifurcation-based MEMS sensors Litvinov, I., Spaer Milo, G., Liberzon, A., & Krylov, S. Applied Physics Letters (2024).

• Effect of overheat and direct flow loading on the MEMS bistable flow sensor Litvinov, I., Refaeli, D., Liberzon, A., & Krylov, S.Sensors and Actuators A: Physical (2024).

• Bistable microbeam-based air flow sensor with piezoresistive snap-through detection Litvinov, I., Spaer Milo, G., Liberzon, A., & Krylov, S.arXiv e-prints (2023).

• On Sampling Rate Limits in Bistable Microbeam Sensors Kessler, Y., Liberzon, A., & Krylov, S.Journal of Microelectromechanical Systems (2021).

• Micro-beam resonator parametrically excited by electro-thermal Joule’s heating and its use as a flow sensor Torteman, B., Kessler, Y., Liberzon, A., et al. Nonlinear Dynamics (2019).

• Buckling response of electrothermally actuated micro-beams to parallel and transverse flow Kessler, Y., Liberzon, A., & Krylov, S. IEEE SENSORS (2016).

Figure from our recent work by Litvinov et al. 2025 [link]