Erez Benjamin

We report a resonant torque-sensing silicon-on-insulator device in which vibrating sensing elements also serve as elastic suspensions and force-amplifying structures. Three double-clamped beams, making an angle of 120 ∘ to each other, are attached to a suspended ring at one of their ends and, at the other end, are anchored to the substrate with an offset from the ring’s center of rotation. Static torque applied to the ring induces rotation of the ring and an axial stress in the beams, thereby altering the beams’ natural frequencies. The lumped model, which accounts for the flexibility of the ring, along with the nonlinear extensible elastica model and full-scale finite element model, were built to estimate the device sensitivity and its dependence on geometric and material parameters. The models show that the amplification of the axial stress and the device sensitivity depend non-monotonically on the anchoring points offset. Two different designs, distinguished by the anchoring offset, were studied experimentally. Frequency sensitivities of 5.4 kHz (nN ⋅ m) − 1 and 7.5 kHz (nN ⋅ m) − 1 were measured, which are in good agreement with the lumped model predictions. Moreover, single-input-single-output actuation and frequency sensing were demonstrated both in finite element simulation and in the experiment.

We report on a new design of an in-plane moving, simple, robust and manufacturable, rotational device with integrated electrostatic actuation. The architecture, based on three off-center anchored beams, enables tailoring of the device bistability, while the combination of high rotational compliance with high lateral stiffness allows to achieve large tilting angles without actuation-related instabilities. The devices were fabricated from silicon on insulator wafers and consistently with the finite elements model prediction, their bistable behaviour and rotation angles up to 11 $^{\circ }$ were demonstrated in the experiment.

We report on the fabrication and characterization of a generic, manufacturable, cantilever-type resonant sensing element, actuated by fringing electrostatic fields and fabricated from a silicon on insulator (SOI) wafer. The architecture of the electrode, designed to be thicker than the cantilever, was tailored to allow efficient electrostatic up-tuning of the beam's frequency and enhancement of the device frequency to voltage/displacement sensitivity in the initial “as fabricated” configuration. The device is not prone to undesired pull-in instability and can be operated at large deflections, which increases the dynamic range. The multilevel structure was fabricated using a two-stage critically timed deep reactive ion etching (DRIE). The device was operated statically and dynamically by a combination of dc and ac voltages, and an increase of the resonant frequency with the increasing voltage/deflection was registered. Consistently with the model predictions, the experimental results suggest that this type of sensing element can be promising for implementation in a large variety of resonant, inertial, force or pressure sensors.

Bistable microstructures demonstrate enhanced responsiveness to external stimuli in the vicinity of the critical configurations that separate stable and unstable states. This makes these devices attractive candidates for implementation in sensors. Here, after a short review of existing bistability-based sensing approaches, we explore the applicability of electrostatically and electro thermally actuated micro beams as flow sensors. Double clamped curved ≈ 1000 μ m long, ≈ 2.8μ m wide and ≈50 μ m thick beams, deep reactive ion etched (DRIE) from a silicon on insulator (SOI) wafer were subject to an air flow in the direction perpendicular to the beam. We show theoretically and experimentally that both the flow-induced cooling of the Joule's heated structure and the drag force reduce the critical snap-through (ST) voltages. The absolute and relative measured sensitivities of the ST voltage of ≈ 1.9 Vsm ^-1 and ≈ 2.6 % sm ^-1 , respectively, are consistent with the Reduced Order (RO) Galerkin model predictions.

We report on a design methodology, fabrication, and characterization of a bistable actuator operated by a parallel-plate electrostatic transducer. The operational principle of the device, which can serve as a bifurcation-based contact-free force/acceleration sensor, is based on a pull-in voltage monitoring. Bistability appears due to the interplay between the hardening nonlinearity of straightened curved beams used as the compliant suspensions and softening nonlinearity of the electrostatic force directed along the beams. Careful mapping of the parameters at the design stage resulted in reduced device sensitivity to fabrication tolerances and allowed to ensure bistability, necessary for the functionality of the sensor. The devices were fabricated from silicon on insulator substrates using deep reactive ion etching and bistability was demonstrated experimentally. Acceleration was emulated using electrostatic force and sensitivity of 0.173 V/g was registered in experiments. Good agreement between the experimental results and the model predictions was observed. [2018-0031]