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
A Combined MEMS Threshold Pressure Sensor and Switch
In this study, a combined threshold pressure sensor
and switch is introduced. The sensor detects when the pressure
drops below a threshold value and automatically triggers a
switch without the need for any computational overhead to
read the pressure or trigger the switch. This system exploits
the significant fluid interaction of a MEMS beam undergoing a
large oscillation from electrostatic levitation to detect changes
in ambient pressure. The levitation electrode configuration is
combined with a parallel-plate system by adding an extra voltage
to an electrode that is traditionally grounded, giving the system
the ability to simultaneously act as a switch by toggling to and
from the pulled-in position. It is experimentally demonstrated
that the pressure sensing/switching mechanism is feasible and
the threshold pressure to trigger the switch can be controlled by
adjusting the voltage applied to the switch electrode.
more »
« less
- Award ID(s):
- 1608692
- PAR ID:
- 10169557
- Date Published:
- Journal Name:
- 2019 IEEE SENSORS
- Page Range / eLocation ID:
- 1 to 4
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
We demonstrate a tunable air pressure switch. The switch detects when the ambient pressure drops below a threshold value and automatically triggers without the need for any computational overhead to read the pressure or trigger the switch. The switch exploits the significant fluid interaction of a MEMS beam undergoing a large oscillation from electrostatic levitation to detect changes in ambient pressure. If the oscillation amplitude near the resonant frequency is above a threshold level, dynamic pull-in is triggered and the switch is closed. The pressure at which the switch closes can be tuned by adjusting the voltage applied to the switch. The use of electrostatic levitation allows the device to be released from their pulled-in position and reused many times without mechanical failure. A theoretical model is derived and validated with experimental data. It is experimentally demonstrated that the pressure switching mechanism is feasible.more » « less
-
This study illustrates the concept of threshold pressure sensing using the parametric resonance of an electrostatic levitation mechanism. The electrostatic levitation allows the oscillations in the opposite direction of the substrate, thereby not limited to small gaps. The pressure sensor detects the pressure drop below a threshold value by triggering the parametric resonance with significant peak to peak dynamic amplitude changes (~ 25 đđ). This detection relies on the fact that the instability region expands when the pressure drop forces the amplitude jump up to the higher oscillation branch. This significant change in the resonator amplitude can be related to a large capacitance variation indicating the threshold pressure. A mathematical model of the resonator is presented to show the working principle of the sensor through frequency response. Our experimental results show that the threshold pressure the sensor detects, can be adjusted by the AC voltage it receives.more » « less
-
We introduce a capacitive MEMS filter that uses electrostatic levitation for actuation and sensing. The advantage of this electrode configuration is that it does not suffer from the pull-in instability and therefore tremendously high voltages can be applied to this system. A large sensing voltage will produce a large output signal, which boosts the signal to noise ratio. The filter outputs about a 110mV peak-to-peak signal when operated at 175V, and can be boosted to 175mV by increasing the voltage to 250V. Because pull-in is eliminated, voltages much higher than 250V can be applied. An outline of the filter design and operating principle is discussed. A model of the filter is derived and analyzed to show the mechanical response and approximate peak-to-peak signal output. This study shows the feasibility of a capacitive sensor that is based on electrostatic levitation, and outlines the advantages it has over traditional parallel-plate electrode configurations. This design is promising for signal signal processing applications where large strokes are important.more » « less
-
more » « less
Abstract Single nanoparticle analysis can reveal how particleâtoâparticle heterogeneity affects ensemble properties derived from traditional bulk measurements. Highâbandwidth, low noise electrochemical measurements are needed to examine the fast heterogeneous electronâtransfer behavior of single nanoparticles with sufficient fidelity to resolve the behavior of individual nanoparticles. Herein, nanopore electrode arrays (NEAs) are fabricated in which each pore supports two vertically spaced, individually addressable electrodes. The top ring electrode serves as a particle gate to control the transport of silver nanoparticles (AgNPs) within individual attoliter volume NEAs nanopores, as shown by redox collisions of AgNPs collisions at the bottom disk electrode. The AgNPânanoporeis system has wideâranging technological applications as well as fundamental interest, since the transport of AgNPs within the NEA mimics the transport of ions through cell membranes via voltageâgated ion channels. A voltage threshold is observed above which AgNPs are able to access the bottom electrode of the NEAs, i.e., a minimum potential at the gate electrode is required to switch between few and many observed collision events on the collector electrode. It is further shown that this threshold voltage is strongly dependent on the applied voltage at both electrodes as well as the size of AgNPs, as shown both experimentally and through finiteâelement modeling. Overall, this study provides a precise method of monitoring nanoparticle transport and in situ redox reactions within nanoconfined spaces at the single particle level.
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1109/SENSORS43011.2019.8956554
