Power MEMS Research Articles

A Novel Real-Time Self-Monitoring RF MEMS Power Sensor for 0.1–30 GHz Applications

A Novel Real-Time Self-Monitoring RF MEMS Power Sensor for 0.1–30 GHz Applications

Design and Simulation of an Ultra-Low-Power Hydrogen Sulfide Gas Sensor with a Cantilever Structure.

Metal oxide gas sensors usually require a few tens of milliwatts of power consumption to operate at high temperature, which limits their application in mobile and portable devices. Here, we proposed a cantilever structure to build an ultra-low power gas sensor for hydrogen sulfide gas detection. By employing a nano-film size effect to reduce the thermal conductivity of the material, and self-heated corrugation configuration, the power consumption of the gas sensor is significantly reduced. Through numerical analysis and finite element simulation, two different gas sensors were designed and the power consumption and stress distribution were analyzed and optimized. Under the operating temperature of 200 °C, only 0.27 mW power is consumed, the stress value is less than 250 MPa and the displacement is a few hundred of nanometers. The results serve as a guide and reference for ultra-low power MEMS device designs.

A High-Performance RF MEMS Power Sensor for Near-Zero Detection Applications

A High-Performance RF MEMS Power Sensor for Near-Zero Detection Applications

Modeling on RF Circuit and Thermal Conduction of a MEMS Amplitude Demodulator

An amplitude demodulator, using an on-line MEMS power sensor is studied in this paper. The model of the equivalent circuit of on-line structure is solved, and the heat transfer model related to the thermopile is proposed and also simulated to verify the feasibility of AM demodulation. Experiments are also performed to verify the proposed models. The microwave performance shows that the device has a return loss that is better than 20 dB, and an insertion loss of less than 0.5 dB up to 10 GHz. Both the model and the experimental results show that the MEMS device can perform demodulation of an AM signal with carrier frequency of 0.01–10 GHz and signal frequency of under 1kHz. [2021-0261]

Macrostructure and macrosegregation behavior of bloom products under various flow control modes of the casting process

Owing to the large cross-section and wide solidification-temperature zone, bloom castings of medium- and high-carbon steels are prone to severe central shrinkage and macrosegregation defects. Flow control technologies such as nozzle injection mode and electromagnetic stirring, together with the casting speed, play a key role in the as-cast macrostructure and macrosegregation distribution in bloom castings achieving soundness and compositional homogeneity of the final as-rolled products. Based on the production process of a medium-carbon-steel bloom casting and its heavy section bars, various flow control modes have been adopted in the casting production to study their effects on the semiproduct solidification structure and the carbon distribution across the bloom section and the following rolled bars. The conventional nozzle with a single straight port shows that the equiaxed crystal ratio in the casting process can only increase from 6.06% to 11.71% with the M-EMS intensity changes from 0 to 800 A, in which a shrinkage cavity and macrosegregation exist along the centerline on the strand casting. While the novel five-port nozzle has been adopted, the equiaxed crystal ratio can reach 23.1% even with the M-EMS power off, and the center cavity index drops down to grade 1.0 or below, meeting the requirement of microvoid flaw detection for the bar products. Additionally, the carbon segregation across the bloom cross-section is observed to resemble an M-shaped curve with a maximum carbon segregation index in the columnar to equiaxed transition zone instead of the popular center region. For the heavy section bars rolled from bloom casting, a similar carbon distribution pattern as the cast is observed after hot working but with an even higher centerline segregation index. Therefore, considering the special quality requirements for the subsequent hot processing, the macrostructure and pattern and intensity of macro-segregation should be regulated from the beginning of casting with a reasonable flow control mode as mentioned in the study.

A New RF MEMS Power Sensor Based on Double-Deck Thermocouples With High Sensitivity and Large Dynamic Range

This letter reports a new RF MEMS power sensor based on double-deck thermocouples with high sensitivity and a large dynamic range. In order to improve RF sensing capability and sensitivity, the double-deck thermocouples and a MEMS substrate membrane are carefully designed. The proposed RF MEMS power sensor is fabricated by GaAs monolithic microwave integrated circuit (MMIC) process coupled with MEMS technology. Experimental result shows that the output thermovoltage of the device has inherent RF-dc linearity with the power from 1 to 500 mW. And the measured return loss is less than -28.6 dB at 1-20 GHz, which exhibits excellent matching characteristics. Moreover, at 8, 10, and 12 GHz, the measured sensitivities are 133.2, 124.3, and 116.8 μV/mW, respectively. Compared with a traditional thermoelectric power sensor, the sensitivity and the dynamic range of the proposed RF MEMS power sensor are increased by approximately 61% and 2.5 times, respectively. The research work can be considered as an incremental improvement of the state of the art (higher power sensing capability and sensitivity) as RF power sensing using double-deck thermocouples.

Energy Scavenging From Low Frequency Vibrations Through a Multi-Pole Thin Magnet and a High-Aspect-Ratio Array Coil

The challenges of developing a micro electromagnetic power generator are to increase the flux density from the thin permanent magnet and reduce the resistance of the micro high-winding-density coil. To overcome these challenges, we propose a novel MEMS power generator for low-frequency-vibration energy harvesting employing a 16-poles thin magnet plate and a high-aspect-ratio spiral micro array coil. Transient magnetic analysis has proved that the multi-pole magnet thin plate (8.9 × 8.9 × t0.5 mm) magnetized by laser assisted heating helps increase the output power from the generator compared with the unidirectional one. The high-aspect-ratio spiral micro array coil (width: 80 µm, thickness: 160 µm, total turns: 144) fabricated by the combination of multilayer SU-8 micro moldings, copper plating, and silver paste screen printing is beneficial for increasing coil density and reducing resistance, thus improving output power. The vibration experiment showed that in terms of no consideration of spring and guideway structure, when the magnet is directly vibrated by an actuator, the induced voltage, generated power, and power density were 1.63 mV, 0.12 µW and 1.03 µW/cm3, respectively at an excitation frequency of 10 Hz with an amplitude of 2 mm. When a 3D-printed cantilever beam was adopted as the spring and guideway structure for the resonant prototype, the counterparts were 8.48 mV, 3.34 µW and 5.22 µW/cm3, respectively at 38 Hz and 2 mm excitation (corresponding to a vibration acceleration peak of 11.6 g).

Crystal Growth of Epitaxial 3C-SiC Thin Film on Si Substrate by Chemical Vapor Deposition using Single Precursor of Vinylsilane

Cubic silicon carbide (3C-SiC) has attracted much attention since it has a wide bandgap, high dielectric breakdown strength, and high thermal stability. 3C-SiC promises various electronic applications such as power devices and MEMS. Also, 3C-SiC has an advantage for a lower cost among many SiC polytypes, as it can grow epitaxially on Si substrate. Generally, two types of precursor source materials, including Si and C, are necessary to grow 3C-SiC thin films for chemical vapor deposition (CVD) method. In addition, complex processes including carbonization with a temperature as high as about 1200 °C are required for conventional epitaxial growth of 3C-SiC [1]. We focus on vinylsilane as a single precursor material for SiC growth. The Si-C bond in vinylsilane is relatively stable due to the relationship of intramolecular bond energy, that is appreciable for SiC growth. The growth of SiC crystals using vinylsilane can be achieved at a low temperature of 1000 ºC or less and the deposition process will be simplified. Recently, we have achieved the formation of polycrystalline SiC thin films on metal substrate using CVD method only with vinylsilane [2]. In this study, we examine the epitaxial growth of 3C-SiC and also report phosphorous (P) doping for SiC thin films grown on Si substrate.SiC thin films were deposited on Si(001) and Si(111) substrates using CVD method with a vinylsilane precursor (manufactured by Japan Advanced Chemicals Co., Ltd.). The substrate temperature of the growth was ranging from 900 to 1000 °C, the growth pressure was 17 kPa, and the growth time was 60 min.The surface morphology of deposited film was observed using scanning electron microscopy (SEM). We can confirm that the uniform morphology of SiC film was formed on the Si substrate for a sample prepared with Si(111) substrate at 1000 ºC and also that there are no voids or defects at the interface.We also examined X-ray diffraction measurements to characterize the crystalline structure. Out-of-plane XRD measurement (2θ/ω method) shows a sufficiently large diffraction peak related to 3C-SiC(111) for the Si(111) sample prepared at 1000 ºC, which means the growth of a well (111)-oriented 3C-SiC thin film on Si(111) substrate. On the other hand, in the case of the grazing angle XRD measurement (2θ method) for the SiC/Si(001) samples prepared at both 900 and 1000 ºC, we observed many diffraction peaks meaning the formation of polycrystalline 3C-SiC. The analysis of peak intensity and full width at half maximum value (FWHM) revealed that the crystallinity of SiC film improved with increasing the growth temperature. Raman scattering spectroscopy measurement also revealed that the dominant bonding structure in the film is Si-C and not C-Hn or C-C for samples prepared at higher than 900 ºC, that means the formation of a high crystalline quality SiC thin film.In our presentation, we will discuss pros and cons of epitaxial growth of SiC films on Si(111) substrates and also reports P-doping into the SiC films will be discussed.

Ultra-low power MEMS micro-heater device

In this paper, we propose a simple design for the heating device with ultra-low power consumption. The device is composed of a micro heater made of Nichrome (20/80) alloy, designed in simple meander shape covering the total surface of S = (1.25 × 104) × (102) µm2. Deposited in thin films with a thickness of 1 µm on square silicon membrane of 14 × 102 µm side and 10 µm of thickness. We used the COMSOL Multiphysics 4.3 a tool for simulation. We achieved a maximum temperature of 900 K by applying 1.5 V of voltage. For gas sensing, the temperature of 707 K is generated at 1.25 V of voltage while the power consumption is 1.25 µW. The maximum relative stress is 3.5 109 N/m2 at 1.5 V. However, at 1.25 V we have less stress of 109 N/m2 and 9.107 × 10− 3 N/m2 for the interface thermo-mechanical strain resulting in good reliability for the device. Finally, the total displacement for the membrane is 50 µm as a maximum when 1.5 V is applied and 35 µm at 1.25 V. this device is perfectly adapted for mobile application as gas sensing and IoT systems.

Electromagnetic-Thermal-Electric Analysis of Indirectly-Heated RF MEMS Power Sensors With Different Terminal Resistor Dimensions

In this article, the design, fabrication and measurements are presented for an indirectly-heated RF MEMS thermoelectric power sensor with different terminal resistor dimensions. In this design, thermal isolation is achieved through a 20μm-thick MEMS substrate membrane using back etching technology. In order to maintain the stability of impedance matching, two low temperature coefficient of resistance (TCR) tantalum nitride (TaN ) resistors of 50 Ω are adopted to serve as heating sources. Considering the effect of the terminal resistor dimension on RF power sensing performance, six configuration sensors have been explored experimentally. Experimental results show that the output response of these devices has excellent RF-DC linearity with the power from 1 mW to 200 mW. And as the dimension of the terminal resistor gradually increases, their sensitivities are 77.3 μV/mW, 63.4 μV/mW, 56.3 μV/mW, 54.4 μV/mW, 49.5 μV/mW and 47.9 μV/mW at 10GHz, respectively. Meanwhile, the measured response time is 3.2 ms, 2.9 ms, 2.7 ms, 2.5 ms, 2.2 ms and 2.0 ms, respectively. This indicates that as the size of the terminal resistor increases, the corresponding sensitivity and response time are decreasing. Therefore, there is a trade-off consideration between high sensitivity and fast response time. Further, an electromagnetic-thermal-electric model of the indirectly-heated RF MEMS power sensor is proposed based on the Seebeck effect and heat transfer theory. Experiments and finite element method (FEM) simulation are performed to verify the validity of the proposed model. The results would be useful to improve future sensor designs and specific applications.

Structural Optimization of Capacitive MEMS Microwave Power Sensor

In this work, a pivoted mechanical model of capacitive MEMS microwave power sensor is established to optimize the relative position of the measuring electrode. The pivoted model is divided into four sections in order to more accurately study the vibration of the cantilever beam. The model of the sensitivity and the overload power are obtained. According to the established model, the structure of the sensor is analyzed and optimized, the relationship of the sensitivity and the overload power with the relative position of the measuring electrode is obtained. ${x}_{3}/{l}=0.9$ is the optimal solution for the overload power, ${x}_{3}/{l}=0.8$ is the optimal solution for the sensitivity, and ${x}_{3}/{l}=0.5$ is taken as the trade-off value to verify the accuracy of the model. Finally, the measured results show that this work has certain reference value and guiding significance for capacitive MEMS power sensors.

A Novel Thermistor-Based RF Power Sensor With Wheatstone Bridge Fabricating on MEMS Membrane

A novel thermistor-based RF power sensor with Wheatstone full-bridge structure is proposed using MEMS technology combined with monolithic microwave integrated circuit (MMIC) process in this paper. A MEMS substrate membrane is carefully designed beneath the hot area by back etching technology. Such a design can effectively suppress the longitudinal heat loss, which facilitates the improvement of sensitivity. In addition, in this design, low TCR (temperature coefficient of resistance) TaN (tantalum nitride) resistors are adopted to achieve the stability of impedance matching. Measurement results show that the output response of this device has excellent linearity with the power from 1 to 200mV. Considering the effect of the distance between the hot and cold areas, three sensor configurations with different arrangements of thermistors were investigated experimentally. And their corresponding sensitivities are 0.16 mV/mW, 0.19 mV/mW and 0.22 mV/mW at 10GHz, respectively. Meanwhile, the measured response times of these three configuration sensors are 20.7 ms, 22.3 ms and 27.2 ms, respectively. Therefore, there is a trade-off consideration between high sensitivity and fast response time. Moreover, the measured return losses are less than −20 dB in the frequency range from 10 MHz to 20GHz. This indicates that these devices have good matching characteristics. The proposed thermistor-based RF MEMS power sensor demonstrates a good performance, especially high sensitivity and stable impedance match, providing great application potential. [2020-0260]

Welcome

Greetings, and welcome to Daytona Beach, FL and PowerMEMS 2018 – the 18th International Conference on Micro and Nanotechnology for Power Generation and Energy Conversion Applications!The objective of PowerMEMS 2018 is to catalyze innovation in micro- and nano-scale technologies for the energy domain. The scope of the meeting ranges from basic principles, to materials and fabrication, to devices, systems and applications. The topics span the lifecycle of energy from power generation or harvesting to storage, conversion and conditioning, and integrated systems that manage these processes. The applications include micro power generation for wireless sensors and portable devices, as well as microsystems for actuation, pumping and propulsion.Our Conference aims to stimulate the exchange of insights and information, as well as the development of new ideas, in the power MEMS field. Our goal is to allow the attendees to interact and network within our multidisciplinary community that includes professionals from many branches of science and engineering, as well as energy and entrepreneurial specialists interested in the commercialization of power MEMS technologies.Since the first PowerMEMS in Sendai, Japan in 2000, the Conference has grown in size, reputation, impact, and technical breadth. This year’s technical program is highlighted by three plenary talks from prominent experts on wearable energy harvesting systems, magneto-electric generators, and near-zero-power microsystems. Each plenary talk anchors a “Focus Session” in each of these themes. The contributed program received 162 abstract and late news submissions. After careful review by the 35-member Technical Program Committee, a total of 135 papers were selected for presentation, 51 for oral, and 84 posters. There oral presentations are divided into 16 sessions, and the posters divided into two afternoon poster sessions. Nine PowerMEMS-in-Action live demos will be featured during the poster sessions, showcasing mature technologies and novel approaches hands-on. The conference proceedings are made available to attendees via direct download. All authors have the option to “elevate” their conference paper into a fully peer-reviewed journal article in either J. Micromechanics and Microengineering or Smart Materials and Structures. All non-elevated conference papers will be archived online around May 2019 under IoP’s J. of Physics: Conference Series.We hope to maximize interaction among participants and stimulate lively discussion through technical and social events. The PowerMEMS School provides opportunity to learn from leading experts in topics ranging from fundamentals of energy harvesting technologies to applications of PowerMEMS in selected domains. The PowerMEMS-in-Action live demos stimulates researchers to push their power MEMS technologies out of the laboratory and get feedback. Our tabletop exhibitors will help catalyze conversations between our industrial partners and the research community. On Thursday, the conference banquet will be held at the Kennedy Space Center, with dinner served directly below the retired Space Shuttle Atlantis orbiter. This will be a once-in-a-lifetime experience!This meeting is made possible by many generous contributions of time, effort, and financial support. Thanks are due to our co-organizers Florian Herrault (TPC Chair), Shad Roundy (Sponsorship and industry Chair), and Alexandra Garraud (School Chair), Peter Woias (PMiA Chair), to the Technical Program Committee for their intensive efforts in reviewing abstract submissions, and to the International Steering Committee for their advice and support. We are grateful to Preferred Meeting Management Inc. for their many contributions to the management and organization of our Conference. Finally, we gratefully acknowledge the organizational and financial support provided for this meeting by the Transducers Research Foundation, Université de Sherbrooke, University of Florida, University of Utah, HRL Laboratories, and our exhibitors, publication partners, and other supporters.We hope that you find PowerMEMS 2018 enjoyable and fruitful, while enjoying the beautiful scenery and unique attractions of Daytona Beach!Sincerely,

3D MEMS In-Chip Solenoid Inductor With High Inductance Density for Power MEMS Device

In this letter, we report the design and measurement of a 3D solenoid inductor that is embedded in a Si substrate and can integrate an iron core. Various inductor designs were fabricated with good structural integrity and repeatability via a CMOS-compatible MEMS fabrication process. The average inductance and quality factor peak-to-peak variation of the inductors was below 10%, which indicates that the fabrication process is repeatable. Among the inductors without iron cores, the highest quality factor (37.6 at 21 MHz) was found in a 5-turn inductor, and the highest inductance and inductance density (respectively, 86.6 nH and 21.7 nH/mm2) were found in a 20-turn inductor. Among the iron-core inductors, the 15-turn inductor had an inductance of 1063 nH and an inductance density of 354.3 nH/mm2, nearly 18 times higher than the same design without an iron core, which is the highest inductance density for a MEMS microinductor to the best of our knowledge. This type of inductor is an important component in RF MEMS and electromagnetic power MEMS devices and can improve their performance and efficiency.

MEMS power generator operated by fluorocarbon gas

This paper proposed a MEMS air turbine generator. The conventional miniature power sources like a battery required a replacement. Therefore, it is limitation for an IoT (Internet of Things) device, and it is required to develop a miniature generator. The proposed generator shows a millimetre scale structure that combined the different technology. The MEMS process is used for the miniature air turbine structure. To achieve the high output power, the electromagnetic induction type is employed. The miniature magnetic circuit is fabricated by the multilayer ceramic technology. Fluorocarbon gas is used as a working fluid to generate the rotational motion of the rotor. By this reason, the miniature power generation system will be realized in the future. Dimensions of the fabricated MEMS power generator were 5.62 mm, 6.17 mm, and 7.12 mm, respectively. The rotational motion was demonstrated using R245fa of fluorocarbon gas. The maximum rotational speed was 154,620rpm when the outside temperature was 46.3 Celsius degree. The output voltage was 10 mV at the load resistance of 1 kΩ. The calculated output power was 0.6 mVA at when the load resistance was 2 Ω.

The Designed MEMS Methane Sensor Based on Pulse Power Supply

As the power too high, the traditional catalytic methane sensor has high wiring cost and quantitative restriction in single circuit. In this paper, a new intelligent methane sensor aimed at low power consumption is designed by using low power MEMS catalytic methane cell, pulse supply mechanism and low power waste circuit. It is observed from the test that the new sensor has low power consumption and well performance.

Silicon Carbide Converters and MEMS Devices for High-temperature Power Electronics: A Critical Review.

The significant advance of power electronics in today’s market is calling for high-performance power conversion systems and MEMS devices that can operate reliably in harsh environments, such as high working temperature. Silicon-carbide (SiC) power electronic devices are featured by the high junction temperature, low power losses, and excellent thermal stability, and thus are attractive to converters and MEMS devices applied in a high-temperature environment. This paper conducts an overview of high-temperature power electronics, with a focus on high-temperature converters and MEMS devices. The critical components, namely SiC power devices and modules, gate drives, and passive components, are introduced and comparatively analyzed regarding composition material, physical structure, and packaging technology. Then, the research and development directions of SiC-based high-temperature converters in the fields of motor drives, rectifier units, DC–DC converters are discussed, as well as MEMS devices. Finally, the existing technical challenges facing high-temperature power electronics are identified, including gate drives, current measurement, parameters matching between each component, and packaging technology.

An MRI Compatible RF MEMs Controlled Wireless Power Transfer System.

In magnetic resonance imaging (MRI), wearable wireless receive coil arrays are a key technology goal. An MRI compatible wireless power transfer (WPT) system will be needed to realize this technology. An MRI WPT system must withstand the extreme electromagnetic environment of the scanner and cannot degrade MRI image quality. Here, a WPT system is developed for operation in MRI scanners using new microelectromechanical RF switch (RF MEMs) technology. The WPT system includes a class-E power amplifier, RF MEMs automated impedance matching, a primary coil array employing RF MEMs power steering, and a flexible secondary coil with class E rectification. To adapt WPT technology to MRI, techniques are developed for operation at high magnetic field, and to mitigate the RF interactions between the scanner and WPT system. A major challenge was the identification and suppression of noise and harmonic interference, by gating, filtering, and rectifier topologies. The system can achieve 63% efficiency while exceeding 13 W delivery over a coil distance of 3.5 cm. For continuous WPT beyond 5W, added filters and full-wave class E rectification lowers harmonic generation at some cost to efficiency, while image SNR reaches about 32% of the ideal. RF-gated WPT, which interrupts power transfer in the MRI signal acquisition interval, achieves SNR performance to within 1 dB of the ideal. With further refinement, the inclusion of WPT technology in MRI scanners appears completely feasible.

A Cross-level Verification Methodology for Digital IPs Augmented with Embedded Timing Monitors

Smart systems are characterized by the integration in a single device of multi-domain subsystems of different technological domains, namely, analog, digital, discrete and power devices, MEMS, and power sources. Such challenges, emerging from the heterogeneous nature of the whole system, combined with the traditional challenges of digital design, directly impact on performance and on propagation delay of digital components. This article proposes a design approach to enhance the RTL model of a given digital component for the integration in smart systems with the automatic insertion of delay sensors, which can detect and correct timing failures. The article then proposes a methodology to verify such added features at system level. The augmented model is abstracted to SystemC TLM, which is automatically injected with mutants (i.e., code mutations) to emulate delays and timing failures. The resulting TLM model is finally simulated to identify timing failures and to verify the correctness of the inserted delay monitors. Experimental results demonstrate the applicability of the proposed design and verification methodology, thanks to an efficient sensor-aware abstraction methodology, by applying the flow to three complex case studies.

Novel Materials and Processes to Develop Viable Thermoelectrics

Thermoelectric power generation which represents the direct solid-state conversion of waste heat to electricity is a promising field challenging to reach wide-scale application. There are intrinsic paradoxes in the requirements of physical properties leading to high thermoelectric performance. Namely, high electrical conductivity but low thermal conductivity κ, and large Seebeck coefficient but high electrical conductivity are required. These have made straightforward enhancement of the thermoelectric performance difficult. I will review several novel materials and processes we are developing to overcome the traditional limitations, and which were presented at this Power MEMS 2017 conference.