Single Substrate Electromagnetic Actuator

A microvalve which utilizes a low temperature ( <300° C.) fabrication process on a single substrate. The valve uses buckling and an electromagnetic actuator to provide a relatively large closing force and lower power consumption. A buckling technique of the membrane is used to provide two stable positions for the membrane, and to reduce the power consumption and the overall size of the microvalve. The use of a permanent magnet is an alternative to the buckled membrane, or it can be used in combination with the buckled membrane, or two sets of micro-coils can be used in order to open and close the valve, providing the capability for the valve to operate under normally opened or normally closed conditions. Magnetic analysis using ANSYS 5.7 shows that the addition of Orthonol between the coils increases the electromagnetic force by more than 1.5 times. At a flow rate of 1 mL/m, the pressure drop is < 100 Pa. The maximum pressure tested was 57 kPa and the time to open or close the valve in air is under 100 ms. This results in an estimated power consumption of 0.1 mW.Georgia Tech Research Corp

MEMS-Based Terahertz Photoacoustic Chemical Sensing System

Advancements in microelectromechanical system (MEMS) technology over the last several decades has been a driving force behind miniaturizing and improving sensor designs. In this work, a specialized cantilever pressure sensor was designed, modeled, and fabricated to investigate the photoacoustic (PA) response of gases to terahertz (THz) radiation under low-vacuum conditions associated with high-resolution spectroscopy. Microfabricated cantilever devices made using silicon-on-insulator (SOI) wafers were tested in a custom-built test chamber in this first ever demonstration of a cantilever-based PA chemical sensor and spectroscopy system in the THz frequency regime. The THz radiation source was amplitude modulated to excite acoustic waves in the chamber, and PA molecular spectroscopy of a gas species was performed. An optical measurement technique was used to evaluate the PA effect on the cantilever sensor; a laser beam was reflected off the cantilever tip and through an iris to a photodiode. As the cantilever movement deflected the laser beam, the beam was clipped by an iris and generated the PA signal. Experimental data indicated a predominantly linear response in signal amplitude from the photodiode measurement technique, which directly correlated to measured cantilever deflections. Using the custom-designed PA chamber and MEMS cantilever sensor, excellent low-pressure PA spectral data of methyl cyanide (CH3CN) at 2 to 40 mTorr range has been obtained. At low chamber pressures, the sensitivity of our system was 1.97 × 10−5 cm−1 and had an excellent normalized noise equivalent absorption (NNEA) coefficient of 1.39 × 10−9 cm−1 W Hz-½ using a 0.5 s signal averaging time

Wireless Remote Weather Monitoring System Based on MEMS Technologies

This study proposes a wireless remote weather monitoring system based on Micro-Electro-Mechanical Systems (MEMS) and wireless sensor network (WSN) technologies comprising sensors for the measurement of temperature, humidity, pressure, wind speed and direction, integrated on a single chip. The sensing signals are transmitted between the Octopus II-A sensor nodes using WSN technology, following amplification and analog/digital conversion (ADC). Experimental results show that the resistance of the micro temperature sensor increases linearly with input temperature, with an average TCR (temperature coefficient of resistance) value of 8.2 × 10−4 (°C−1). The resistance of the pressure sensor also increases linearly with air pressure, with an average sensitivity value of 3.5 × 10−2 (Ω/kPa). The sensitivity to humidity increases with ambient temperature due to the effect of temperature on the dielectric constant, which was determined to be 16.9, 21.4, 27.0, and 38.2 (pF/%RH) at 27 °C, 30 °C, 40 °C, and 50 °C, respectively. The velocity of airflow is obtained by summing the variations in resistor response as airflow passed over the sensors providing sensitivity of 4.2 × 10−2, 9.2 × 10−2, 9.7 × 10−2 (Ω/ms−1) with power consumption by the heating resistor of 0.2, 0.3, and 0.5 W, respectively. The passage of air across the surface of the flow sensors prompts variations in temperature among each of the sensing resistors. Evaluating these variations in resistance caused by the temperature change enables the measurement of wind direction

A MEMS-Based Flow Rate and Flow Direction Sensing Platform with Integrated Temperature Compensation Scheme

This study develops a MEMS-based low-cost sensing platform for sensing gas flow rate and flow direction comprising four silicon nitride cantilever beams arranged in a cross-form configuration, a circular hot-wire flow meter suspended on a silicon nitride membrane, and an integrated resistive temperature detector (RTD). In the proposed device, the flow rate is inversely derived from the change in the resistance signal of the flow meter when exposed to the sensed air stream. To compensate for the effects of the ambient temperature on the accuracy of the flow rate measurements, the output signal from the flow meter is compensated using the resistance signal generated by the RTD. As air travels over the surface of the cross-form cantilever structure, the upstream cantilevers are deflected in the downward direction, while the downstream cantilevers are deflected in the upward direction. The deflection of the cantilever beams causes a corresponding change in the resistive signals of the piezoresistors patterned on their upper surfaces. The amount by which each beam deflects depends on both the flow rate and the orientation of the beam relative to the direction of the gas flow. Thus, following an appropriate compensation by the temperature-corrected flow rate, the gas flow direction can be determined through a suitable manipulation of the output signals of the four piezoresistors. The experimental results have confirmed that the resulting variation in the output signals of the integrated sensors can be used to determine not only the ambient temperature and the velocity of the air flow, but also its direction relative to the sensor with an accuracy of ± 7.5° error

Micromachined Artificial Haircell

A micromachined artificial sensor comprises a support coupled to and movable with respect to a substrate. A polymer, high-aspect ratio cilia-like structure is disposed on and extends out-of-plane from the support. A strain detector is disposed with respect to the support to detect movement of the support

DESIGN, MODELING AND CHARACTERIZATION OF A PIEZOELECTRIC ENERGY HARVESTING DEVICE

The mechanical vibratory energy has been extracted based on the car engine’s frequency and converted into an electrical energy by making use of a bimorph piezoelectric harvesting device; this process is called energy harvesting. The output of that energy used to power-up small electronics devices such as electronic transmitters and sensors which utilize low voltage and current (1-5 Volt / 10 - 20 mA). A cantilever of Lead-Zirconate-Titanate (PbZrO3TiO2) with dimensions of (40 × 10 × 0.5 mm) has been analyzed and it’s produced an output power in the range of (100μW - 0.4mW) at resonance frequency of (≤ 0.2 KHz) under peak acceleration of (≤ 10 m/s2). This cantilever’s targeted vibration is dynamic (damped) vibration; therefore it has been subjected into continuous vibratory force. The Static Vibration is run at the first stages to check the working force and stamina of the cantilever by applying a pulse of movement and observe the response of the transient wave of the cantilever. The project aims to design and model a bimorph piezoelectric (PZT) cantilever device uses the effects of piezoelectric property to extract the mechanical vibration that is generated based on the car engine compartment’s specifications and convert it to electrical energy. Successfully, a bimorph piezoelectric harvester cantilever was designed under the optimal conditions identified in this report to extract the car engine vibration produced by dynamic vibration shaker using the typical frequencies and acceleration of the car engine and produced output power nearly 0.39 mW when converts this extracted vibration to electrical energ

MEMS tunable infrared metamaterial and mechanical sensors

Sub-wavelength resonant structures open the path for fine controlling the near-field at the nanoscale dimension. They constitute into macroscopic “metamaterials” with macroscale properties such as transmission, reflection, and absorption being tailored to exhibit a particular electromagnetic response. The properties of the resonators are often fixed at the time of fabrication wherein the tunability is demanding to overcome fabrication tolerances and afford fast signal processing. Hybridizing dynamic components such as optically active medium into the device makes tunable devices. Microelectromechanical systems (MEMS) compatible integrated circuit fabrication process is a promising platform that can be merged with photonics or novel 2D materials. The prospect of enormous freedom in integrating nanophotonics, MEMS actuators and sensors, and microelectronics into a single platform has driven the rapid development of MEMS-based sensing devices. This thesis describes the design and development of four tunable plasmonic structures based on active media or MEMS, two graphene-based MEMS sensors and a novel tape-based cost-effective nanotransfer printing techniques. First of all, we present two tunable plasmonic devices with the use of two active medium, which are electrically controlled liquid crystals and temperature-responsive hydrogels, respectively. By incorporating a nematic liquid crystal layer into quasi-3D mushroom plasmonic nanostructures and thanks to the unique coupling between surface plasmon polariton and Rayleigh anomaly, we have achieved the electrical tuning of the properties of plasmonic crystal at a low operating electric field. We also present another tunable plasmonic device with the capability to sense environmental temperature variations. The device is bowtie nanoantenna arrays coated with a submicron-thick, thermos-responsive hydrogel. The favorable scaling of plasmonic dimers at the nanometer scale and ionic diffusion at the submicron scale is leveraged to achieve strong optical resonance and rapid hydrogel response, respectively. Secondly, we present two MEMS -based tunable near-to-mid infrared metamaterials on a silicon-on-insulator wafer via electrically and thermally actuating the freestanding nanocantilevers. The two devices are developed on the basis of the same fabrication process and are easy-to-implement. The electrostatically driven metamaterial affords ultrahigh mechanical modulation (several tens of MHz) of an optical signal while the thermo-mechanically tunable metamaterial provides up to 90% optical signal modulation at a wavelength of 3.6 õm. Next, we present MEMS graphene-based pressure and gas flow sensors realized by transferring a large area and few-layered graphene onto a suspended silicon nitride thin membrane perforated with micro-through-holes. Due to the increased strain in the through-holes, the pressure sensor exhibits a very high sensitivty outperformed than most existing MEMS-based pressure sensors using graphene, silicon, and carbon nanotubes. An air flow sensor is also demonstrated via patterning graphene sheets with flow-through microholes. The flow rate of the air is measured by converting the mechanically deflection of the membrane into the electrical readout due to the graphene piezeroresistors. Finally, we present a tape-based multifunctional nanotransfer printing process based on a simple stick-and-peel procedure. It affords fast production of large-area metallic and dielectric nanophotonic sensing devices and metamaterials using Scotch tape