- Award ID(s):
- 1608692
- PAR ID:
- 10061886
- Date Published:
- Journal Name:
- ASME International Design Engineering Technical Conferences
- Page Range / eLocation ID:
- V004T09A005 (7 pages)
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
We present a MEMS microphone that converts the mechanical motion of a diaphragm, generated by acoustic waves, to an electrical output voltage by capacitive fingers. The sensitivity of a microphone is one of the most important properties of its design. The sensitivity is proportional to the applied bias voltage. However, it is limited by the pull-in voltage, which causes the parallel plates to collapse and prevents the device from functioning properly. The presented MEMS microphone is biased by repulsive force instead of attractive force to avoid pull-in instability. A unit module of the repulsive force sensor consists of a grounded moving finger directly above a grounded fixed finger placed between two horizontally seperated voltage fixed fingers. The moving finger experiences an asymmetric electrostatic field that generates repulsive force that pushes it away from the substrate. Because of the repulsive nature of the force, the applied voltage can be increased for better sensitivity without the risk of pull-in failure. To date, the repulsive force has been used to engage a MEMS actuator such as a micro-mirror, but we now apply it for a capacitive sensor. Using the repulsive force can revolutionize capacitive sensors in many applications because they will achieve better sensitivity. Our simulations show that the repulsive force allows us to improve the sensitivity by increasing the bias voltage. The applied voltage and the back volume of a standard microphone have stiffening effects that significantly reduce its sensitivity. We find that proper design of the back volume and capacitive fingers yield promising results without pull-in instability.more » « less
-
In this paper a novel electrostatic MEMS combined shock sensor and normally-closed switch is presented. The switch uses combined attractive and repulsive forcing to toggle a cantilever beam to and from the pulled-in position. The attractive force is generated through a parallel plate electrode configuration and induces pull-in. The repulsive force is generated through electrostatic levitation from a third electrode and serves to pull the beam out of its pulled-in position. A triboelectric transducer converts impact energy to electrical energy to provide voltage for the third electrode, which temporarily opens the switch if enough impact energy is supplied. Triboelectricity addresses the high voltage requirement for electrostatic levitation. The multi-electrode sensor also addresses the low current output from the generator because it acts as an open circuit between the parallel plate and levitation electrodes. A theoretical model of the switch is derived to analyze stability and the dynamic response of the cantilever. Threshold voltages to pull-in and release the beam through repulsive forcing is calculated. Output voltage plots from a prototype generator under a single impact are applied to the sensor-switch model to demonstrate the working principle of the sensor-switch is feasible.more » « less
-
MEMS electrostatic actuators are used in optical applications because of their small size and quick response. However, nonlinearities of electrostatic force, long settling-time and small range of motion significantly hampers their performance. Adding electrostatic levitation to MEMS parallel-plate mechanism, we achieved a wide linear operation region away from the center electrode. Because of linearity, command-shaping becomes an easy and effective method to decrease the settling-time and overshoot. Compared to the conventional parallel-plate electrodes, we have shown a considerable increase in the travel range of levitating electrodes using double-step command signals.more » « less
-
Quantum and thermal fluctuations are fundamental to a plethora of phenomena within quantum optics, including the Casimir effect that acts between closely separated surfaces typically found in microelectromechanical systems (MEMS) and nanoelectromechanical systems (NEMS) devices. Particularly promising for engineering and harnessing these forces are systems out of thermal equilibrium. Recently, semiconductors with external bias have been proposed to study the nonequilibrium Casimir force. Here, we explore systems involving moderately biased semiconductors that exhibit strong repulsive Casimir forces, and we determine the effects of bias voltage, semiconductor bandgap energy, and separation for experimentally accessible configurations. Modes emitted from the semiconductors exert a repulsive force on a near surface that overcomes the attractive equilibrium Casimir force contribution at submicron distances. For the geometry of two parallel planes, those modes undergo Fabry–Pérot interference resulting in an oscillatory force behavior as a function of separation. Utilizing the proximity-force approximation, we predict that the repulsive force exerted on a gold sphere is well within the accuracy of typical Casimir force experiments. Our work opens up new possibilities for controlling forces at the nanometer and micrometer scale with applications in sensing and actuation in nanotechnology.
-
The use of parametric oscillator start-up principles applied to a MEMS-based super-regenerative receiver front-end obviates the need for a positive feedback sustaining amplifier and permits OOK input detection with sensitivity better than −67 dBm using only 15 µW of pump power, which is 33 times smaller than the previous published mark of 490 μW using MEMS [1]. Here, removal of the sustaining amplifier (and its 489 μW) and instigation of oscillator start-up via parametric means permit use of a much lower power oscillator, e.g., a ring oscillator, to pump the RF front-end detecting resonator at double its resonance frequency while retaining acceptable receiver sensitivity. The substantial reduction in power consumption afforded by this method is compelling for IoT applications, where power is paramount, especially for wireless communications.more » « less