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3 pages, 143 KiB

Open AccessEditorial

Editorial for the Special Issue on MEMS/NEMS Sensors: Fabrication and Application

by Goutam Koley

Micromachines 2019, 10(9), 554; https://doi.org/10.3390/mi10090554 - 22 Aug 2019

Cited by 2 | Viewed by 2186

Abstract

MEMS sensors are currently undergoing a phase of exciting technological development, not only enabling advancements in traditional applications such as accelerometers and gyroscopes, but also in emerging applications such as microfluidics, thermoelectromechanical, and harsh environment sensors [...] Full article

(This article belongs to the Special Issue MEMS/NEMS Sensors: Fabrication and Application)

Research

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15 pages, 4490 KiB

Open AccessArticle

Design of a Micromachined Z-axis Tunneling Magnetoresistive Accelerometer with Electrostatic Force Feedback

by Bo Yang, Binlong Wang, Hongyu Yan and Xiaoyong Gao

Micromachines 2019, 10(2), 158; https://doi.org/10.3390/mi10020158 - 25 Feb 2019

Cited by 13 | Viewed by 4143

Abstract

This paper presents the design, simulation, fabrication and experiments of a micromachined z-axis tunneling magnetoresistive accelerometer with electrostatic force feedback. The tunneling magnetoresistive accelerometer consists of two upper differential tunneling magnetoresistive sensors, a middle plane main structure with permanent magnetic films and lower [...] Read more.

This paper presents the design, simulation, fabrication and experiments of a micromachined z-axis tunneling magnetoresistive accelerometer with electrostatic force feedback. The tunneling magnetoresistive accelerometer consists of two upper differential tunneling magnetoresistive sensors, a middle plane main structure with permanent magnetic films and lower electrostatic feedback electrodes. A pair of lever-driven differential proof masses in the middle plane main structure is used for sensitiveness to acceleration and closed-loop feedback control. The tunneling magnetoresistive effect with high sensitivity is adopted to measure magnetic field variation caused by input acceleration. The structural mode and mass ratio between inner and outer proof masses are optimized by the Ansys simulation. Simultaneously, the magnetic field characteristic simulation is implemented to analyze the effect of the location of tunneling magnetoresistive sensors, magnetic field intensity, and the dimension of permanent magnetic film on magnetic field sensitivity, which is beneficial for the achievement of maximum sensitivity. The micromachined z-axis tunneling magnetoresistive accelerometer fabricated by the standard deep dry silicon on glass (DDSOG) process has a device dimension of 6400 μm (length) × 6400 μm (width) × 120 μm (height). The experimental results demonstrate the prototype has a maximal sensitivity of 8.85 mV/g along the z-axis sensitive direction under the gap of 1 mm. Simultaneously, Allan variance analysis illustrate that a noise floor of 86.2 μg/Hz^0.5 is implemented in the z-axis tunneling magnetoresistive accelerometer. Full article

(This article belongs to the Special Issue MEMS/NEMS Sensors: Fabrication and Application)

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13 pages, 2699 KiB

Open AccessArticle

The Effect of the Anisotropy of Single Crystal Silicon on the Frequency Split of Vibrating Ring Gyroscopes

by Zhengcheng Qin, Yang Gao, Jia Jia, Xukai Ding, Libin Huang and Hongsheng Li

Micromachines 2019, 10(2), 126; https://doi.org/10.3390/mi10020126 - 14 Feb 2019

Cited by 21 | Viewed by 4579

Abstract

This paper analyzes the effect of the anisotropy of single crystal silicon on the frequency split of the vibrating ring gyroscope, operated in the

n = 2

wineglass mode. Firstly, the elastic properties including elastic matrices and orthotropic elasticity values of (100) and [...] Read more.

This paper analyzes the effect of the anisotropy of single crystal silicon on the frequency split of the vibrating ring gyroscope, operated in the

n = 2

wineglass mode. Firstly, the elastic properties including elastic matrices and orthotropic elasticity values of (100) and (111) silicon wafers were calculated using the direction cosines of transformed coordinate systems. The (111) wafer was found to be in-plane isotropic. Then, the frequency splits of the

n = 2

mode ring gyroscopes of two wafers were simulated using the calculated elastic properties. The simulation results show that the frequency split of the (100) ring gyroscope is far larger than that of the (111) ring gyroscope. Finally, experimental verifications were carried out on the micro-gyroscopes fabricated using deep dry silicon on glass technology. The experimental results are sufficiently in agreement with those of the simulation. Although the single crystal silicon is anisotropic, all the results show that compared with the (100) ring gyroscope, the frequency split of the ring gyroscope fabricated using the (111) wafer is less affected by the crystal direction, which demonstrates that the (111) wafer is more suitable for use in silicon ring gyroscopes as it is possible to get a lower frequency split. Full article

(This article belongs to the Special Issue MEMS/NEMS Sensors: Fabrication and Application)

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14 pages, 2606 KiB

Open AccessArticle

Evolution of Si Crystallographic Planes-Etching of Square and Circle Patterns in 25 wt % TMAH

by Milče M. Smiljanić, Žarko Lazić, Branislav Radjenović, Marija Radmilović-Radjenović and Vesna Jović

Micromachines 2019, 10(2), 102; https://doi.org/10.3390/mi10020102 - 31 Jan 2019

Cited by 12 | Viewed by 5639

Abstract

Squares and circles are basic patterns for most mask designs of silicon microdevices. Evolution of etched Si crystallographic planes defined by square and circle patterns in the masking layer is presented and analyzed in this paper. The sides of square patterns in the [...] Read more.

Squares and circles are basic patterns for most mask designs of silicon microdevices. Evolution of etched Si crystallographic planes defined by square and circle patterns in the masking layer is presented and analyzed in this paper. The sides of square patterns in the masking layer are designed along predetermined <n10> crystallographic directions. Etching of a (100) silicon substrate is performed in 25 wt % tetramethylammonium hydroxide (TMAH) water solution at the temperature of 80 °C. Additionally, this paper presents three-dimensional (3D) simulations of the profile evolution during silicon etching of designed patterns based on the level-set method. We analyzed etching of designed patterns in the shape of square and circle islands. The crystallographic planes that appear during etching of 3D structures in the experiment and simulated etching profiles are determined. A good agreement between dominant crystallographic planes through experiments and simulations is obtained. The etch rates of dominant exposed crystallographic planes are also analytically calculated. Full article

(This article belongs to the Special Issue MEMS/NEMS Sensors: Fabrication and Application)

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11 pages, 6833 KiB

Open AccessArticle

A Novel Fabricating Process of Catalytic Gas Sensor Based on Droplet Generating Technology

by Liqun Wu, Ting Zhang, Hongcheng Wang, Chengxin Tang and Linan Zhang

Micromachines 2019, 10(1), 71; https://doi.org/10.3390/mi10010071 - 20 Jan 2019

Cited by 11 | Viewed by 4150

Abstract

Catalytic gas sensors are widely used for measuring concentrations of combustible gases to prevent explosive accidents in industrial and domestic environments. The typical structure of the sensitive element of the sensor consists of carrier and catalyst materials, which are in and around a [...] Read more.

Catalytic gas sensors are widely used for measuring concentrations of combustible gases to prevent explosive accidents in industrial and domestic environments. The typical structure of the sensitive element of the sensor consists of carrier and catalyst materials, which are in and around a platinum coil. However, the size of the platinum coil is micron-grade and typically has a cylindrical shape. It is extremely difficult to control the amount of carrier and catalyst materials and to fulfill the inner cavity of the coil, which adds to the irreproducibility and uncertainty of the sensor performance. To solve this problem, this paper presents a new method which uses a drop-on-demand droplet generator to add the carrier and catalytic materials into the platinum coil and fabricate the micropellistor. The materials in this article include finely dispersed Al₂O₃ suspension and platinum palladium (Pd-Pt) catalyst. The size of the micropellistor with carrier material can be controlled by the number of the suspension droplets, while the amount of Pd-Pt catalyst can be controlled by the number of catalyst droplets. A bridge circuit is used to obtain the output signal of the gas sensors. The original signals of the micropellistor at 140 mV and 80 mV remain after aging treatment. The sensitivity and power consumption of the pellistor are 32 mV/% CH₄ and 120 mW, respectively. Full article

(This article belongs to the Special Issue MEMS/NEMS Sensors: Fabrication and Application)

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15 pages, 11715 KiB

Open AccessArticle

Implementation of a CMOS/MEMS Accelerometer with ASIC Processes

by Yu-Sian Liu and Kuei-Ann Wen

Micromachines 2019, 10(1), 50; https://doi.org/10.3390/mi10010050 - 12 Jan 2019

Cited by 22 | Viewed by 5757

Abstract

This paper presents the design, simulation and mechanical characterization of a newly proposed complementary metal-oxide semiconductor (CMOS)/micro-electromechanical system (MEMS) accelerometer. The monolithic CMOS/MEMS accelerometer was fabricated using the 0.18 μm application-specific integrated circuit (ASIC)-compatible CMOS/MEMS process. An approximate analytical model for the spring [...] Read more.

This paper presents the design, simulation and mechanical characterization of a newly proposed complementary metal-oxide semiconductor (CMOS)/micro-electromechanical system (MEMS) accelerometer. The monolithic CMOS/MEMS accelerometer was fabricated using the 0.18 μm application-specific integrated circuit (ASIC)-compatible CMOS/MEMS process. An approximate analytical model for the spring design is presented. The experiments showed that the resonant frequency of the proposed tri-axis accelerometer was around 5.35 kHz for out-plane vibration. The tri-axis accelerometer had an area of 1096 μm × 1256 μm. Full article

(This article belongs to the Special Issue MEMS/NEMS Sensors: Fabrication and Application)

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11 pages, 3374 KiB

Open AccessArticle

Bonding Strength of a Glass Microfluidic Device Fabricated by Femtosecond Laser Micromachining and Direct Welding

by Sungil Kim, Jeongtae Kim, Yeun-Ho Joung, Jiyeon Choi and Chiwan Koo

Micromachines 2018, 9(12), 639; https://doi.org/10.3390/mi9120639 - 3 Dec 2018

Cited by 41 | Viewed by 9313

Abstract

We present a rapid and highly reliable glass (fused silica) microfluidic device fabrication process using various laser processes, including maskless microchannel formation and packaging. Femtosecond laser assisted selective etching was adopted to pattern microfluidic channels on a glass substrate and direct welding was [...] Read more.

We present a rapid and highly reliable glass (fused silica) microfluidic device fabrication process using various laser processes, including maskless microchannel formation and packaging. Femtosecond laser assisted selective etching was adopted to pattern microfluidic channels on a glass substrate and direct welding was applied for local melting of the glass interface in the vicinity of the microchannels. To pattern channels, a pulse energy of 10 μJ was used with a scanning speed of 100 mm/s at a pulse repetition rate of 500 kHz. After 20–30 min of etching in hydrofluoric acid (HF), the glass was welded with a pulse energy of 2.7 μJ and a speed of 20 mm/s. The developed process was as simple as drawing, but powerful enough to reduce the entire production time to an hour. To investigate the welding strength of the fabricated glass device, we increased the hydraulic pressure inside the microchannel of the glass device integrated into a custom-built pressure measurement system and monitored the internal pressure. The glass device showed extremely reliable bonding by enduring internal pressure up to at least 1.4 MPa without any leakage or breakage. The measured pressure is 3.5-fold higher than the maximum internal pressure of the conventional polydimethylsiloxane (PDMS)–glass or PDMS–PDMS bonding. The demonstrated laser process can be applied to produce a new class of glass devices with reliability in a high pressure environment, which cannot be achieved by PDMS devices or ultraviolet (UV) glued glass devices. Full article

(This article belongs to the Special Issue MEMS/NEMS Sensors: Fabrication and Application)

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14 pages, 6364 KiB

Open AccessArticle

Monolithic Low Noise and Low Zero-g Offset CMOS/MEMS Accelerometer Readout Scheme

by Yu-Sian Liu and Kuei-Ann Wen

Micromachines 2018, 9(12), 637; https://doi.org/10.3390/mi9120637 - 30 Nov 2018

Cited by 6 | Viewed by 4163

Abstract

A monolithic low noise and low zero-g offset CMOS/MEMS accelerometer and readout scheme in standard 0.18 μm CMOS mixed signal UMC process is presented. The low noise chopper architecture and telescopic topology is developed to achieve low noise. The experiments show noise floor [...] Read more.

A monolithic low noise and low zero-g offset CMOS/MEMS accelerometer and readout scheme in standard 0.18 μm CMOS mixed signal UMC process is presented. The low noise chopper architecture and telescopic topology is developed to achieve low noise. The experiments show noise floor is 421.70 μg/√Hz. The whole system has 470 mV/g sensitivity. The power consumption is about 1.67 mW. The zero-g trimming circuit reduces the offset from 1242.63 mg to 2.30 mg. Full article

(This article belongs to the Special Issue MEMS/NEMS Sensors: Fabrication and Application)

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12 pages, 2308 KiB

Open AccessArticle

A 5 g Inertial Micro-Switch with Enhanced Threshold Accuracy Using Squeeze-Film Damping

by Yingchun Peng, Guoguo Wu, Chunpeng Pan, Cheng Lv and Tianhong Luo

Micromachines 2018, 9(11), 539; https://doi.org/10.3390/mi9110539 - 23 Oct 2018

Cited by 3 | Viewed by 2750

Abstract

Our previous report based on a 10 g (gravity) silicon-based inertial micro-switch showed that the contact effect between the two electrodes can be improved by squeeze-film damping. As an extended study toward its potential applications, the switch with a large proof mass suspended [...] Read more.

Our previous report based on a 10 g (gravity) silicon-based inertial micro-switch showed that the contact effect between the two electrodes can be improved by squeeze-film damping. As an extended study toward its potential applications, the switch with a large proof mass suspended by four flexible serpentine springs was redesigned to achieve 5 g threshold value and enhanced threshold accuracy. The impact of the squeeze-film damping on the threshold value was theoretically studied. The theoretical results show that the threshold variation from the designed value due to fabrication errors can be reduced by optimizing the device thickness (the thickness of the proof mass and springs) and then establishing a tradeoff between the damping and elastic forces, thus improving the threshold accuracy. The design strategy was verified by FEM (finite-element-method) simulation and an experimental test. The simulation results show that the maximum threshold deviation was only 0.15 g, when the device thickness variation range was 16–24 μm, which is an adequately wide latitude for the current bulk silicon micromachining technology. The measured threshold values were 4.9–5.8 g and the device thicknesses were 18.2–22.5 μm, agreeing well with the simulation results. The measured contact time was 50 μs which is also in good agreement with our previous work. Full article

(This article belongs to the Special Issue MEMS/NEMS Sensors: Fabrication and Application)

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12 pages, 5115 KiB

Open AccessFeature PaperArticle

Thermal Performance of Micro Hotplates with Novel Shapes Based on Single-Layer SiO₂ Suspended Film

by Qi Liu, Guifu Ding, Yipin Wang and Jinyuan Yao

Micromachines 2018, 9(10), 514; https://doi.org/10.3390/mi9100514 - 11 Oct 2018

Cited by 16 | Viewed by 4342

Abstract

In this paper, two kinds of suspended micro hotplate with novel shapes of multibeam structure and reticular structure are designed. These designs have a reliable mechanical strength, so they can be designed and fabricated on single-layer SiO₂ suspended film through a simplified [...] Read more.

In this paper, two kinds of suspended micro hotplate with novel shapes of multibeam structure and reticular structure are designed. These designs have a reliable mechanical strength, so they can be designed and fabricated on single-layer SiO₂ suspended film through a simplified process. Single-layer suspended film helps to reduce power consumption. Based on the new film shapes, different resistance heaters with various widths and thicknesses are designed. Then, the temperature uniformity and power consumption of different micro hotplates are compared to study the effect of these variables and obtain the one with the optimal thermal performance. We report the simulations of temperature uniformity and give the corresponding infrared images in measurement. The experimental temperature differences are larger than those of the simulation. Experimental results show that the lowest power consumption and the minimum temperature difference are 43 mW and 50 °C, respectively, when the highest temperature on the suspended platform (240 × 240 μm²) is 450 °C. Compared to the traditional four-beam micro hotplate, temperature non-uniformity is reduced by about 30–50%. Full article

(This article belongs to the Special Issue MEMS/NEMS Sensors: Fabrication and Application)

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18 pages, 11851 KiB

Open AccessArticle

Automatic Frequency Tuning Technology for Dual-Mass MEMS Gyroscope Based on a Quadrature Modulation Signal

by Jia Jia, Xukai Ding, Yang Gao and Hongsheng Li

Micromachines 2018, 9(10), 511; https://doi.org/10.3390/mi9100511 - 10 Oct 2018

Cited by 17 | Viewed by 4139

Abstract

In order to eliminate the frequency mismatch of MEMS (Microelectromechanical Systems) gyroscopes, this paper proposes a frequency tuning technology based on a quadrature modulation signal. A sinusoidal signal having a frequency greater the gyroscope operating bandwidth is applied to the quadrature stiffness correction [...] Read more.

In order to eliminate the frequency mismatch of MEMS (Microelectromechanical Systems) gyroscopes, this paper proposes a frequency tuning technology based on a quadrature modulation signal. A sinusoidal signal having a frequency greater the gyroscope operating bandwidth is applied to the quadrature stiffness correction combs, and the modulation signal containing the frequency split information is then excited at the gyroscope output. The effects of quadrature correction combs and frequency tuning combs on the resonant frequency of gyroscope are analyzed. The tuning principle based on low frequency input excitation is analyzed, and the tuning system adopting this principle is designed and simulated. The experiments are arranged to verify the theoretical analysis. The wide temperature range test (-20

^{\circ} C

–60

^{\circ} C

) demonstrates the reliability of the tuning system with a maximum mismatch frequency of less than 0.3 Hz. The scale factor test and static test were carried out at three temperature conditions (−20

^{\circ}

C, room temperature, 60

^{\circ}

C), and the scale factor, zero-bias instability, and angle random walk are improved. Moreover, the closed-loop detection method is adopted, which improves the scale factor nonlinearity and bandwidth under the premise of maintaining the same static performances compared with the open-loop detection by tuning. Full article

(This article belongs to the Special Issue MEMS/NEMS Sensors: Fabrication and Application)

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9 pages, 6613 KiB

Open AccessArticle

Miniaturized NIR Spectrometer Based on Novel MOEMS Scanning Tilted Grating

by Jian Huang, Quan Wen, Qiuyu Nie, Fei Chang, Ying Zhou and Zhiyu Wen

Micromachines 2018, 9(10), 478; https://doi.org/10.3390/mi9100478 - 20 Sep 2018

Cited by 31 | Viewed by 4265

Abstract

This paper presents a dispersive near-infrared spectrometer with features of miniaturization, portability and low cost. The application of a resonantly-driven scanning grating mirror (SGM) as a dispersive element in a crossed Czerny–Turner configuration enables the design of a miniaturized spectrometer that can detect [...] Read more.

This paper presents a dispersive near-infrared spectrometer with features of miniaturization, portability and low cost. The application of a resonantly-driven scanning grating mirror (SGM) as a dispersive element in a crossed Czerny–Turner configuration enables the design of a miniaturized spectrometer that can detect the full spectra using only one single InGaAs diode. In addition, a high accuracy recalculation is realized, which can convert time-dependent measurements to spectrum information by utilizing the deflection position detector integrated on SGM and its associated closed-loop control circuit. Finally, the spectrometer prototype is subjected to a series of tests to characterize the instrument’s performance fully. The results of the experiment show that the spectrometer works in a spectral range of 800 nm–1800 nm with a resolution of less than 10 nm, a size of 9 × 7 × 7 cm³, a wavelength stability better than ±1 nm and a measuring time of less than 1 ms. Furthermore, the power consumption of the instrument is 3 W at 5 V DC, and the signal-to-noise ratio is 3267 at full scale. Therefore, this spectrometer could be a potential alternative to classical spectrometers in process control applications or could be used as a portable or airborne spectroscopic sensor. Full article

(This article belongs to the Special Issue MEMS/NEMS Sensors: Fabrication and Application)

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10 pages, 3367 KiB

Open AccessArticle

Design, Simulation and Experimental Study of the Linear Magnetic Microactuator

by Hanlin Feng, Xiaodan Miao and Zhuoqing Yang

Micromachines 2018, 9(9), 454; https://doi.org/10.3390/mi9090454 - 11 Sep 2018

Cited by 9 | Viewed by 4284

Abstract

This paper reports the design, simulation and experimental study of a linear magnetic microactuator for portable electronic equipment and microsatellite high resolution remote sensing technology. The linear magnetic microactuator consists of a planar microcoil, a supporter and a microspring. Its bistable mechanism can [...] Read more.

This paper reports the design, simulation and experimental study of a linear magnetic microactuator for portable electronic equipment and microsatellite high resolution remote sensing technology. The linear magnetic microactuator consists of a planar microcoil, a supporter and a microspring. Its bistable mechanism can be kept without current by external permanent magnetic force, and can be switched by the bidirectional electromagnetic force. The linearization and threshold of the bistable mechanism was optimized by topology structure design of the microspring. The linear microactuator was then fabricated based on non-silicon technology and the prototype was tested. The testing results indicated that the bistable mechanism was realized with a fast response of 0.96 ms, which verified the simulation and analysis. Full article

(This article belongs to the Special Issue MEMS/NEMS Sensors: Fabrication and Application)

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11 pages, 4365 KiB

Open AccessArticle

Frequency Characteristic of Resonant Micro Fluidic Chip for Oil Detection Based on Resistance Parameter

by Zilei Yu, Lin Zeng, Hongpeng Zhang, Guogang Yang, Wenqi Wang and Wanheng Zhang

Micromachines 2018, 9(7), 344; https://doi.org/10.3390/mi9070344 - 9 Jul 2018

Cited by 17 | Viewed by 3467

Abstract

Monitoring the working condition of hydraulic equipment is significance in industrial fields. The abnormal wear of the hydraulic system can be revealed by detecting the variety and size of micro metal debris in the hydraulic oil. We thus present the design and implementation [...] Read more.

Monitoring the working condition of hydraulic equipment is significance in industrial fields. The abnormal wear of the hydraulic system can be revealed by detecting the variety and size of micro metal debris in the hydraulic oil. We thus present the design and implementation of a micro detection system of hydraulic oil metal debris based on inductor capacitor (LC) resonant circuit in this paper. By changing the resonant frequency of the micro fluidic chip, we can detect the metal debris of hydraulic oil and analyze the sensitivity of the micro fluidic chip at different resonant frequencies. We then obtained the most suitable resonant frequency. The chip would generate a positive resistance pulse when the iron particles pass through the detection area and the sensitivity of the chip decreased with resonant frequency. The chip would generate a negative resistance pulse when the copper particles pass through the detection area and the sensitivity of the chip increased with resonant frequency. The experimental results show that the change of resonant frequency has a great effect on the copper particles and little on the iron particles. Thus, a relatively big resonant frequency can be selected for chip designing and testing. In practice, we can choose a relatively big resonant frequency in this micro fluidic chip designing. The resonant micro fluidic chip is capable of detecting 20–30 μm iron particles and 70–80 μm copper particles at 0.9 MHz resonant frequency. Full article

(This article belongs to the Special Issue MEMS/NEMS Sensors: Fabrication and Application)

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13 pages, 3863 KiB

Open AccessArticle

Adaptive Backstepping Design of a Microgyroscope

by Yunmei Fang, Juntao Fei and Yuzheng Yang

Micromachines 2018, 9(7), 338; https://doi.org/10.3390/mi9070338 - 3 Jul 2018

Cited by 60 | Viewed by 4179

Abstract

This paper presents a novel algorithm for the design and analysis of an adaptive backstepping controller (ABC) for a microgyroscope. Firstly, Lagrange–Maxwell electromechanical equations are established to derive the dynamic model of a z-axis microgyroscope. Secondly, a nonlinear controller as a backstepping [...] Read more.

This paper presents a novel algorithm for the design and analysis of an adaptive backstepping controller (ABC) for a microgyroscope. Firstly, Lagrange–Maxwell electromechanical equations are established to derive the dynamic model of a z-axis microgyroscope. Secondly, a nonlinear controller as a backstepping design approach is introduced and deployed in order to drive the trajectory tracking errors to converge to zero with asymptotic stability. Meanwhile, an adaptive estimator is developed and implemented with the backstepping controller to update the value of the parameter estimates in the Lyapunov framework in real-time. In addition, the unknown system parameters including the angular velocity may be estimated online if the persistent excitation (PE) requirement is met. A robust compensator is incorporated in the adaptive backstepping algorithm to suppress the parameter variations and external disturbances. Finally, simulation studies are conducted to prove the validity of the proposed ABC scheme with guaranteed asymptotic stability and excellent tracking performance, as well as consistent parameter estimates in the presence of model uncertainties and disturbances. Full article

(This article belongs to the Special Issue MEMS/NEMS Sensors: Fabrication and Application)

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9 pages, 3175 KiB

Open AccessFeature PaperArticle

High Temperature AlGaN/GaN Membrane Based Pressure Sensors

by Durga Gajula, Ifat Jahangir and Goutam Koley

Micromachines 2018, 9(5), 207; https://doi.org/10.3390/mi9050207 - 28 Apr 2018

Cited by 22 | Viewed by 5235

Abstract

A highly sensitive Gallium Nitride (GaN) diaphragm based micro-scale pressure sensor with an AlGaN/GaN heterostructure field effect transistor (HFET) deflection transducer has been designed and fabricated for high temperature applications. The performance of the pressure sensor was studied over a pressure range of [...] Read more.

A highly sensitive Gallium Nitride (GaN) diaphragm based micro-scale pressure sensor with an AlGaN/GaN heterostructure field effect transistor (HFET) deflection transducer has been designed and fabricated for high temperature applications. The performance of the pressure sensor was studied over a pressure range of 20 kPa, which resulted in an ultra-high sensitivity of ~0.76%/kPa, with a signal-to-noise ratio as high as 16 dB, when biased optimally in the subthreshold region. A high gauge factor of 260 was determined from strain distribution in the sensor membrane obtained from finite element simulations. A repeatable sensor performance was observed over multiple pressure cycles up to a temperature of 200 °C. Full article

(This article belongs to the Special Issue MEMS/NEMS Sensors: Fabrication and Application)

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11 pages, 38993 KiB

Open AccessArticle

DC-25 GHz and Low-Loss MEMS Thermoelectric Power Sensors with Floating Thermal Slug and Reliable Back Cavity Based on GaAs MMIC Technology

by Zhiqiang Zhang and Yao Ma

Micromachines 2018, 9(4), 154; https://doi.org/10.3390/mi9040154 - 29 Mar 2018

Cited by 8 | Viewed by 4467

Abstract

Wideband and low-loss microwave power measurements are becoming increasingly important for microwave communication and radar systems. To achieve such a power measurement, this paper presents the design and measurement of wideband DC-25 GHz and low-loss MEMS thermoelectric power sensors with a floating thermal [...] Read more.

Wideband and low-loss microwave power measurements are becoming increasingly important for microwave communication and radar systems. To achieve such a power measurement, this paper presents the design and measurement of wideband DC-25 GHz and low-loss MEMS thermoelectric power sensors with a floating thermal slug and a reliable back cavity. In the sensors, the microwave power is converted to thermovoltages via heat. The collaborative design of the thermal slug and the back cavity, i.e., two thermal flow paths, is utilized to improve the efficiency of heat transfer and to ensure reliable applications. These sensors are required to operate up to 25 GHz. In order to achieve low microwave losses at the bandwidth, the floating thermal slug is designed instead of the grounded one. The effects of the floating slug on the reflection losses are analyzed by the simulation. The fabrication of these sensors is completed by GaAs monolithic microwave integrated circuits (MMIC) and micro-electro-mechanical systems (MEMS) technology. Measured reflection losses are less than −25.6 dB up to 12 GHz and −18.6 dB up to 25 GHz. The design of the floating thermal slug reduces the losses, which is equivalent to improving the sensitivity. At 10 and 25 GHz, experiments exhibit that the sensors result in sensitivities of about 51.13 and 35.28 μV/mW for the floating slug and 81.68 and 55.20 μV/mW for the floating slug and the cavity. Full article

(This article belongs to the Special Issue MEMS/NEMS Sensors: Fabrication and Application)

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31 pages, 6690 KiB

Open AccessReview

Applications of Photonic Crystal Nanobeam Cavities for Sensing

by Qifeng Qiao, Ji Xia, Chengkuo Lee and Guangya Zhou

Micromachines 2018, 9(11), 541; https://doi.org/10.3390/mi9110541 - 23 Oct 2018

Cited by 61 | Viewed by 8143

Abstract

In recent years, there has been growing interest in optical sensors based on microcavities due to their advantages of size reduction and enhanced sensing capability. In this paper, we aim to give a comprehensive review of the field of photonic crystal nanobeam cavity-based [...] Read more.

In recent years, there has been growing interest in optical sensors based on microcavities due to their advantages of size reduction and enhanced sensing capability. In this paper, we aim to give a comprehensive review of the field of photonic crystal nanobeam cavity-based sensors. The sensing principles and development of applications, such as refractive index sensing, nanoparticle sensing, optomechanical sensing, and temperature sensing, are summarized and highlighted. From the studies reported, it is demonstrated that photonic crystal nanobeam cavities, which provide excellent light confinement capability, ultra-small size, flexible on-chip design, and easy integration, offer promising platforms for a range of sensing applications. Full article

(This article belongs to the Special Issue MEMS/NEMS Sensors: Fabrication and Application)

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