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In this paper, a sensor using a complementary split ring resonator (CSRR) is proposed for non-destructive testing of blood glucose. By depicting the complementary split ring structure on the ground, the electromagnetic field strength between the split rings can be enhanced effectively. The structure size of the sensor by CSRR is determined by simulation, so that the insertion loss curve of the device has a resonance point at the frequency of 3.419 GHz. With a special holder created by three-dimensional (3D) printing technology, the test platform was established when the concentration of the solution varied from 0 mg/mL to 20 mg/mL. The experimental results indicate that there is an obvious linear relationship between the insertion loss S21 and the glucose concentration at the resonant frequency. Similarly, the measured real part and imaginary part of the S21 both vary with glucose concentration linearly. Based on the above experimental results, the feasibility of the sensor using a CSRR proposed in this paper for non-destructive detection of blood glucose is preliminarily verified. [ABSTRACT FROM AUTHOR]

This communication investigated the dust effect on microelectromechanical system (MEMS) thermal wind sensors, with an aim to evaluate performance in practical applications. An equivalent circuit was established to analyze the temperature gradient influenced by dust accumulation on the sensor's surface. The finite element method (FEM) simulation was carried out to verify the proposed model using COMSOL Multiphysics software. In experiments, dust was accumulated on the sensor's surface by two different methods. The measured results indicated that the output voltage for the sensor with dust on its surface was a little smaller than that of the sensor without dust at the same wind speed, which can degrade the measurement sensitivity and accuracy. Compared to the sensor without dust, the average voltage was reduced by about 1.91% and 3.75% when the dustiness was 0.04 g/mL and 0.12 g/mL, respectively. The results can provide a reference for the actual application of thermal wind sensors in harsh environments. [ABSTRACT FROM AUTHOR]

An analytic model of dual-layer-structure (DLS) microelectromechanical system (MEMS) thermal wind sensor was proposed in this article. Heat conduction and heat convective theory were applied to obtain the temperature difference between upstream and downstream under different wind speeds and directions. Simulation by finite element method (FEM) was performed to verify the proposed model. The DLS MEMS wind sensor was fabricated by commercial foundry with two polysilicon layers and one metal layer. After being packaged, the wind sensor was tested based on front surface sensing mode in the wind tunnel up to 33 m/s. The results demonstrated that the wind speed measurement agrees with the proposed model well and the average error of output voltage was no more than 8 mV. Moreover, the measured wind direction increased with the actual value marked on the base from 0° to 360°, which was consistent with the established model. Moreover, the average error was close to 3.7° and the maximum value was no more than 6.38°, which may be caused by asymmetry in scribing and packaging. [ABSTRACT FROM AUTHOR]

In this article, the benchmark drift of micromachined thermal wind sensor due to the packaging asymmetry has been analyzed and compensated. For the ideal wind sensors with symmetric packaging, the benchmark does not vary with speed and direction. However, for the real sensors, especially for handmade ones, packaging asymmetry problems are usually inevitable. Consequently, benchmark drifts with wind because of different thermal distribution in each direction, which was verified by the proposed lumped parameters model. The real sensors were tested in a wind tunnel and results showed the benchmark drift as well. The contribution of this work lies in the establishment of the equation of benchmark dependent on wind speed, which can predict benchmark value under different wind speeds by calibration at zero wind speed. This compensation method is extremely simple and convenient for industrial production. After compensation, the relative wind speed errors are reduced from 46 to 8% up to 30 m/s, and the wind direction errors are reduced from 30° to 7° over the full range of 360°. [ABSTRACT FROM AUTHOR]

A novel flexible LC-type wind speed sensor, as well as its readout circuit, is proposed in this paper. Two inductors are designed on both surface of the flexible substrate, connecting by a parallel plate capacitor. Hence, substrate bending induced by wind can change the total inductance, then shifting the resonant frequency of this LC-type speed sensor. The readout circuit is designed and realized on the PCB board. The LC-type sensor is tested in the wind tunnel and the readout circuit outputs the frequency spectrum. The experiments demonstrate that the resonant frequency increases with the wind speed up to 25m/s. The measured sensitivity is close to 39.8kHz/(m/s), 50.8kHz/(m/s) and 57.7kHz/(m/s) for the sensor with windward height of 30mm, 40mm and 50mm, respectively. Although large windward height can improve the sensitivity, it’s easy to saturate and the maximum detectable speed is reduced. [ABSTRACT FROM AUTHOR]

In this article, a novel micro-electromechanical systems (MEMS) thermal wind sensor using the plastic injection packaging method was proposed. Compared with previous devices suffering from packaging asymmetry, the presented design can relieve the drift phenomenon and improve the accuracy of wind detection. Lumped parameter model and finite-element method (FEM) simulation were developed, and the sensor’s improvement was validated. By means of plastic injection molding process, the MEMS sensor chip based on ceramic substrate was encapsulated in a plastic carrier with low thermal conductivity of 0.96 W/($\text{m} \!\cdot \!\text{K}$). In addition, individual packaging was implemented by laser cutting, which ensures that the geometric center of the chip is almost coincident with that of packaging. The sensor, operated in the constant temperature difference (CTD) mode, was tested in the wind tunnel. The experimental results show that wind speed is measured up to 30 m/s with an accuracy of ±7%, while the direction is characterized over the full range of 360° with errors less than ±5°. Compared with the device in our previous work, the measurement accuracy of the proposed prototype sensor was improved by more than two times because of effective benchmark drift suppression. [ABSTRACT FROM AUTHOR]

In this paper, the design, fabrication, and characterization of a robust MEMS thermal wind sensor utilizing ceramic film packaging are proposed. The ceramic film is fabricated by means of low temperature co-fired ceramic (LTCC) technology, achieving the excellent adhesion between silicon substrate and ceramic film without any thermal adhesive. The most important is that the adverse effects of the packaging on the performance of the thermal wind sensor can be minimized by adjusting the thickness and thermal conductivity of the ceramic film during the preparation of the ceramic slurry. The influences of thickness and thermal conductivity of ceramic film on the performance of sensor have been simulated by finite element method, and the results are in reasonable agreement with theoretical analysis. The proposed sensors were tested and calibrated in a wind tunnel. Experiments results demonstrate that the sensitivity of the proposed sensor is decreased only 4.7%, compared with the sensor without ceramic film. The maximum measurement error of the proposed sensor in wind speed and direction is 0.66 m/s and 5°, respectively. Compared with the sensor packaged with $250\mu \text{m}$ ceramic carrier, the heating power of the proposed sensor is reduced by nearly 50% and the sensitivity is increased by an order of magnitude at the same time. [ABSTRACT FROM AUTHOR]

A thermal wind sensor utilizes the fact that airflow over a heated plate will cool it asymmetrically, with the upstream part of the plate being cooled more than the downstream part. In the temperature-balanced (TB) mode, the heating power may be distributed spatially in the sensor such that any flow-induced temperature gradient is cancelled. Information about the airflow can be extracted in the distribution of heating power in the sensor. Ideally, the influence of changes in the ambient temperature on the sensor’s output can be eliminated if in the whole measurement range the temperature sensor sensitivities are equal. However, because of the temperature dependency of the material properties of the airflow and the sensor, it may have a temperature drift. This paper, for the first time, investigates temperature effects of the ceramic microelectromechanical system (MEMS) thermal wind sensor based on the TB mode. The sensor consists of four outlying heaters and four inlying thermistors in two orthogonal directions on a ceramic substrate. When working in the TB mode, it could measure wind speed and wind direction by applying a power difference on the upstream and downstream heaters, so that the flow-induced temperature gradient is eliminated. Theoretical analysis has been developed which takes the variations of thermophysical properties in the sensor and the control circuits into account. Experiments for testing wind speed and direction have been performed in a wind tunnel with an adjustable ambient temperature. It shows that the wind speed is linearly influenced by the ambient temperature while the wind direction is inherently unaffected by ambient temperature variations. After compensation, the sensor shows a credible performance with an error of less than ±1m/s in wind speed and ±2° in wind direction in a temperature range from 0 °C to 30 °C. [ABSTRACT FROM AUTHOR]

This paper presents a semi-empirical model for the temperature effect of a micromachined 2-D anemometer. The anemometer consists of a self-heated double Wheatstone bridge. Eight thermistors are symmetrically arranged in two orthogonal directions, and four of them in each direction make up a Wheatstone bridge. The eight thermistors simultaneously act as both heating and sensing elements. The terminal voltage across the bridge and the bridge output voltage, under the constant current supply, are utilized to measure the wind speed and direction, respectively. The semi-empirical model has taken the thermal physical properties of the air, sensor substrate, and thermistors into account. It shows that the measurement of wind direction has a weak temperature dependence due to the symmetric config uration of the self-heated double Wheatstone bridge, which suppresses the temperature drift. The temperature compensation has been performed by means of the semi-empirical model. The experimental measurements demonstrate that, when the air temperature changes from 270 to 310 K, the wind speed varies from 0 to 30 m/s with an error less than ±1.5 m/s while the wind direction spans from 0° to 360° with the weak temperature dependence. [ABSTRACT FROM AUTHOR]

A 2-D anemometer sensor on a ceramic substrate is proposed, modeled, simulated, and fabricated. The sensor consists of four outlying heaters and four inlying thermistors arranged in two orthogonal directions on a ceramic substrate. The heaters are driven by power feedback control circuits, while the thermistors measure the temperature distribution on the surface of the sensor. By applying a power difference on the upstream and downstream heaters, the flow-induced temperature gradient is canceled via the temperature-balanced mode, and both wind speed and direction can be extracted by the applied power difference. An analytical model of the 2-D anemometer sensor is developed for the applied power difference as a function of wind speed and direction. The finite-element method simulations have been utilized to demonstrate the analytical model. The sensor was fabricated directly on the ceramic substrate by using a typical lift-off technology. The sensor output was measured and compared with the theoretical model. A high measurement accuracy has been achieved from 0 to 40 m/s with a speed error less than ±0.5m/s and a direction error of less than ±2°. [ABSTRACT FROM AUTHOR]

Modeling of the packaged wind sensor operating on constant power (CP) mode is proposed in this paper. The proposed model is based on the theory of heat conduction and forced convection. The presented model indicates that the total output dc voltage is proportional to the square root of the wind speed, and ${V}_{x}$ , as well as ${V}_{y}$ , varies with the wind direction based on cosine function. The wind sensor is fabricated by microelectromechanical systems (MEMS) technology and packaged with the glue. The test is performed in the wind tunnel and the measured results indicate an agreement with the presented model. The relative error of voltage for the wind speed is less than 14% up to 30 m/s, while that for the wind direction is no more than 10.7% from 0° to 360°. [ABSTRACT FROM AUTHOR]

A self-heated double Wheatstone bridge configuration for a 2-D wind sensor is presented. Without a central heating element, eight thermistors are symmetrically arranged in two orthogonal directions, and four of them in each direction make up a Wheatstone bridge. The eight thermistors simultaneously act as the heating sources and temperature sensing elements. By applying the constant current supply to the bridge, the terminal voltage across the bridge and the bridge output voltage are utilized to measure the wind speed and direction, respectively. The 2-D wind sensor has been simulated numerically and fabricated directly on the ceramic substrate. Experiments demonstrate that the measured speed varies from 0 to 40 m/s with an error less than ±2 m/s while the measured direction spans from 0° to 360° with an error less than ±3° after calibration. The double bridge configuration greatly simplifies the measurement and control circuits for the 2-D wind sensor. [2018-0171] [ABSTRACT FROM AUTHOR]

In this Letter, a differential piezoresitive wind speed sensor on a flexible substrate is proposed. Two piezoresistors with the same size are fabricated on the front surface and back surface of the substrate, respectively. When the wind blows towards the device, the flexible substrate is bent, increasing the resistance on the front surface and reducing that on the back surface. The proposed sensor is fabricated on a polyethylene terephthalate substrate. Wind speed experiments are performed in the wind tunnel and the results demonstrate that the sensor can measure the wind speed up to about 20 m/s. [ABSTRACT FROM AUTHOR]

This paper introduces a novel sensing element scheme to improve the accuracy of 2-D micromachined thermal wind sensor. The sensing element consists of eight heaters and eight thermistors placed on ceramic substrate. The octagon-arranged sixteen resistors are divided into two wind sensing groups, cross-type group and saltire-type group. These two groups monitor wind independently, and the final measured wind speed and direction are extracted from the measurement results of the two groups. Based on this octagon-sensing design, the sensor achieves higher accuracy for wind measurement, which is verified by the experiment. The results show that for the wind speed up to 33 m/s, the sensor has a measurement error less than ±1%, and the airflow direction over the full range of 360° is determined with a maximum error of ±1.5°. [2018-0045] [ABSTRACT FROM AUTHOR]

In this paper, the effect of insulation trenches on micromachined silicon thermal wind sensors is explored. The sensor is composed of a central heater and four thermistors. It measures wind speed and direction through detecting the airflow-induced temperature difference on the chip surface. Three different forms of insulation trenches are designed and fabricated to explore their effects on the performance of wind sensors. The experimental results show that when the sensors work in constant voltage mode, the center and arch trenches enhance the performance, while the arch trenches have the most significant effect on the sensitivity improvement. Moreover, all the three kinds of insulation trenches reduce the power consumption for the sensors operated in constant temperature difference mode. The insulation trench design in this paper can provide a valuable reference for the design and fabrication of micromachined silicon thermal wind sensors. [ABSTRACT FROM PUBLISHER]

This paper presents the design, fabrication, and performance of a micromachined silicon thermal wind sensor with improved sensitivity. Deep reactive ion etching (DRIE) trenches are fabricated between the heater and the thermistors to suppress the lateral heat conduction in the chip. In addition, eight thermistors symmetrically arranged in four directions around the heater form two Wheatstone full-bridges, resulting in about 50% increase of the sensitivity with respect to four thermistors. Based on these two methods, the sensitivity of the micromachined silicon thermal wind sensor is improved remarkably, which is verified by the experiment. The results show that the measurement wind speed range is up to 33 m/s in constant voltage (CV) mode with the initial heating power of 256 mW. The sensitivity is measured to be 29.37 mV/ms−1 at the wind speed 3.3 m/s, achieving improvement of about 226%, compared with that of the traditional wind sensor. Wind direction measurement results show that airflow direction over the full range of 360° is determined with an accuracy of ±5°. [2017-0052] [ABSTRACT FROM AUTHOR]

This paper builds a complete analytical model for self-assembling microwave power sensor with thermopile and curled cantilever beam. The power sensor consists of a thermoelectric power sensor for low power detection from 0.1 mW to 100 mW and a capacitive power sensor for high power detection from 100 mW to 800 mW. The curled cantilever beam is designed to improve the dynamic range and microwave performance of the power sensor. The analytical model includes an electromagnetic model, a static mechanical model, and a stationary heat transfer model. The electromagnetic model takes the S-parameter of indirect-heating thermoelectric power sensor into consideration. The static mechanical model considers the fringing fields between the curled cantilever beam and the measuring electrode as well as the initial curling induced by the stress gradient. The experimental results show a good agreement with the theory and validate the effectiveness of the presented models. Furthermore, good performance of the power sensor has found. The measured return loss is lower than −25.5 dB at 8–12 GHz and the output of the power sensor has good linearity with the incident radio frequency power up to 600 mW. [ABSTRACT FROM AUTHOR]

The cascaded power sensor, including terminating-type one and capacitive-type one is modeled in this paper. The electric-heat-electric conversion model in the terminating-type power sensor is based on Fourier conduction equation, and the electric-force-electric conversion model in the capacitive-type power sensor is based on strain equation. Experiments are performed to verify the model. For the incident power from 1 to 100 mW, the measured sensitivity of the terminating-type is 0.124 mV/mW and the sensitivity of the model is 0.135 mV/mW. For the incident power from 100 to 150 mW, the sensitivity of the capacitive-type sensor is about 0.156 fF/mW, while the calculated sensitivity of the model is 0.165 fF/mW. The comparison demonstrates that the related error of the voltage is less than 9% and the related error of the capacitance change is less than 6%. [ABSTRACT FROM PUBLISHER]

In this paper, we report a novel and low-cost method to improve the sensitivity of a low-power 2D microelectromechanical systems thermal wind sensor by using HF wet etching. After wet etching, the thickness of the glass substrate decreases, so that the sensor’s thermal vias become more exposed to the wind. As a result, the conductive heat transfer is weakened and the convective heat transfer is enhanced in sensor operation. Finite-element method simulations verify this analysis. Moreover, the sensor chips with different lengths of silicon vias above the substrate are successfully fabricated and tested. Measurement results show that the wet etching has no influence on the metal film sensing and heating elements of the sensor. Besides, before and after wet etching for 7 and 14 min, at the wind speed of 5 m/s, the measured sensitivities of the sensor with a total power consumption of 24.5 mW are 77.2, 98.6, and 164.1 mK/(m/s). Measurement results also show that the improved sensitivity of the sensor chip can provide a more accurate measurement in wind speed but has little effect on the wind direction measurement. Instead, the accuracy of wind direction measurement is mainly related to the structural and thermal symmetries of the wind sensor. After compensation, the proposed thermal wind sensor can detect the wind direction in a full range of 360° with an mean error of 2.3° and a maximum error of 6°. [ABSTRACT FROM PUBLISHER]

In this paper, an integrated sensor for microwave power and frequency measurement is proposed for 1–10 GHz application. The novelty is that this device cannot only measure microwave power but also can realize microwave frequency measurement at the same time. The incident power is dissipated and converted heat by two loaded resistors, and then detected indirectly by output voltage based on Seebeck effect. A microelectromechanical system (MEMS) coupler is designed over the coplanar waveguide transmission line and the coupled power varies with the frequency of the signal. Therefore, by measuring the coupled power, the frequency of the signal can be deduced. This integrated power and frequency sensor is fabricated by GaAs monolithic microwave integrated circuit process and MEMS technology. The measured return loss is about −26 dB at 1 GHz and −22 dB at 10 GHz. The power measurement indicates that the sensitivity is close to 0.116 mV/mW at 1 GHz and 0.110 mV/mW at 10 GHz. The frequency measurement is performed and the sensitivity is close to 0.035 mV/GHz under the incident power of 60 mW. [ABSTRACT FROM PUBLISHER]

A 2-D MEMS wind sensor based on $\Delta \text{P}$ (power difference) thermal feedback control is presented. The sensor consists of four outlying heaters and four inlying thermistors in two orthogonal directions on ceramic substrate. A $\Delta \text{P}$ thermal feedback control system is applied to eliminate the flow-induced temperature difference between upstream and downstream so as to achieve a temperature-balanced mode. This applied power difference among the four heaters is a measure for the wind speed and direction. Experimental results demonstrate that the measured speed varies from 0 to 40 m/s with an error less than ±0.5 m/s while the measured direction spans from 0° to 360° with an error less than ±2°. [2017-0286] [ABSTRACT FROM AUTHOR]

A reliability-enhanced power sensor is proposed based on a metal–insulator–metal (MIM) capacitor. The coupled power by the MIM capacitor is a small part and the transmitted power is most of the incident power. Hence, the transmitted power is for low power measurement while the coupled power is used as high power detection. The proposed power sensor is fabricated by a GaAs monolithic microwave integrated circuit process. The measured return loss is greater than 21 dB over the frequency band of 8–12 GHz. When the incident power increases from 1 to 100 mW, the output voltage increases linearly and the sensitivity is measured to be about 0.125 mV/mW at 8 GHz, 0.114 mV/mW at 10 GHz, and 0.109 mV/mW at 12 GHz, respectively. For the incident power from 100 to 200 mW, a part of the incident power is coupled by the MIM capacitor and the measured sensitivity is about 15.8 \mu \textV /mW at 8 GHz, 15.4~\mu \textV /mW at 10 GHz, and 15.8 \mu \textV /mW at 12 GHz, respectively. [ABSTRACT FROM PUBLISHER]

In this paper, a novel in-line type frequency detector is proposed based on a MEMS membrane for X-band applications. In this design, the MEMS membrane stands above the signal line of the CPW transmission line and acts as a coupling capacitance. A certain percentage of the incident power, as a function of the frequency, is coupled to the microwave power sensors. Finally, the frequency of the incident RF signal is able to be deduced by measuring the output thermovoltage of the microwave power sensor based on the Seebeck effect. The design, lumped equivalent circuit model and simulation are presented. The in-line type power sensor is fabricated by the GaAs MMIC process based on MEMS technology. The measured return loss is less than −13 dB and the insertion loss is better than 1.3 dB over the frequency band of 8–12 GHz. The RF frequency measurement demonstrates that the output thermovoltage increases from 0.22 to 0.35 mV when the frequency varies from 8 to 12 GHz under the input power of 10 dBm. [ABSTRACT FROM AUTHOR]

ABSTRACT This article presents an X-band Wilkinson power divider which is completely compatible with GaAs monolithic microwave integrated circuit (MMIC). The novelty is that, GaAs is chosen for the realization for substrate because of its excellent microwave performance, and Au is used to fabricate transmission lines and air bridges due to its good electric properties. The measured return loss of port 1 is about −32 dB at the center frequency of 9 GHz and less than −16 dB over X-band. The insertion loss of port 2 and 3 is close to 3.3 dB at 8-12 GHz. The measured bandwidth for which the input return loss is less than −20 dB is about 3.2 GHz. For the miniaturized power divider, the measured return loss of port 1 is about −23 dB at the center frequency of 11 GHz and less than −13 dB over the band of 8-12 GHz. The measured insertion loss of port 2 and 3 is close to 3.5 dB over the X-band. The measured bandwidth of the miniaturized divider is less than 1.6 GHz. Comparison between the Wilkinson power divider and the miniaturized one shows that the shorter the quarter-wave transmission line is, the larger the impedance is. Meanwhile, the chip area reduction also leads to narrowed bandwidth of the power divider. The experiments demonstrate that the MMIC chip area of the power divider has been reduced by nearly 50% by capacitive loading, whereas the bandwidth is also narrowed by 50%. Therefore, the Wilkinson power divider applies to the situation if wide bandwidth is needed, while the miniaturized one is a better solution for small chip area. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:700-705, 2014 [ABSTRACT FROM AUTHOR]

An 8-12 GHz microwave frequency detector is presented, which is based on MEMS power sensors, by sensing the phase delay of two separated signals in two different tracks. The phase delay, proportional to frequency of the input microwave signal, leads to variation of the output power. Two different kinds of MEMS power sensors, a thermoelectric microwave power sensor and a MEMS capacitive power sensor, are adopted to measure the variation. The former is used for measuring the lower power while the latter for the higher one. The presented detector has been designed, optimized and fabricated successfully using the GaAs MMIC process. For the microwave signals of 10, 15 and 20 dBm, the measured result shows that the output thermovoltage decreases with the frequency based on the thermoelectric microwave power sensor and sensitivities of the detector better than 0.033, 0.110 and 0.343 µVMHz-1 are measured, respectively. Furthermore, the sensitivity of detector is directly proportional to the power of the input microwave signal. For the microwave signals of 24 dBm, the measured result shows that the capacitance decreases with the frequency based on the MEMS capacitive power sensor and the sensitivity of 0.013 fF MHz-1 is measured. The frequency measurement demonstrates the validity of the presented design. [ABSTRACT FROM AUTHOR]

In this letter, a differential capacitive power sensor is proposed based on the seesaw-type microelectromechanical systems (MEMS) membrane. When the microwave power is applied, the center part of the membrane is pulled down toward to the substrate. Meanwhile, the end parts are turned away from the substrate, because two anchors act like pivots. Hence, the capacitance between the center part and the electrodes increases, while the capacitance induced by the end parts decreases. This device is based on the MEMS technology and fabricated by GaAs monolithic microwave integrated circuit (MMIC) process. The tested return loss is about −29 dB at 1 GHz, −18 dB at 5 GHz, and −13 dB at 10 GHz. The insertion loss is better than 1.5 dB over 1–10 GHz. For the incident power from 1 to 100 mW, the measured capacitance change magnitude \Delta C\mathrm {in} increases from 0.1 to 7fF, while the capacitance change \Delta C\mathrm {out} magnitude varies from 0.1 to about 3 fF. Therefore, the sensitivity of the proposed power sensor is improved and on the order of 0.1 fF/mW. [2016-0014] [ABSTRACT FROM PUBLISHER]

In this letter, a new cascaded terminating-type and capacitive-type power sensor is proposed for −10- to 22-dBm application. The terminating-type power sensor is designed for the low-power detection, while the capacitive-type power sensor is for high-power detection. This device is based on microelectromechanical systems (MEMS) technology and fabricated by GaAs monolithic microwave integrated circuit process. The tested return loss is about −23 dB at 8 GHz, −21.5 dB at 10 GHz, and −20 dB at 12 GHz. For the incident power from 1 to 100 mW, the terminating-type sensor operates, and the measured sensitivity is close to 0.132 mV/mW at 8 GHz, 0.124 mV/mW at 10 GHz, and 0.125 mV/mW at 12 GHz, respectively. For the incident power from 100 to 150 mW, the capacitive-type sensor works, and the measured sensitivity is about 0.160 fF/mW at 8 GHz, 0.156 fF/mW at 10 GHz, and 0.145 fF/mW at 12 GHz, respectively. [ABSTRACT FROM AUTHOR]

A high dynamic range microwave power sensor compatible with the gallium arsenide monolithic microwave integrated circuit process is presented. The power sensor consists of a thermoelectric power sensor and a capacitive power sensor for low and high power detection, respectively. To improve the dynamic range and optimise the impedance matching characteristic, the curled cantilever beam is utilised and the slot width of the coplanar waveguide transmission line is modified. The measured return loss is lower than –25.5 dB at 8–12 GHz. The output of the power sensor shows good linearity with the incident radio frequency power. For the incident power from 0.1 to 100 mW, the obtained sensitivities by a thermoelectric power sensor are about 0.0842, 0.0752 and 0.0701 mV/mW at 8, 10 and 12 GHz, respectively. For the incident power from 100 to 400 mW, the measured sensitivities by the capacitive power senor are about 0.0400, 0.0301 and 0.199 fF/mW at 8, 10 and 12 GHz, respectively. [ABSTRACT FROM AUTHOR]

In this paper, a novel 2.5-dimensional (2.5D) flexible wind sensor is proposed based on four differential plate capacitors. This design consists of a windward pillar, two electrode layers, and a support layer, which are all made of polydimethylsiloxane (PDMS) with different Young's moduli. A 2 mm × 2 mm copper electrode array is located on each electrode layer, forming four parallel plate capacitors as the sensitive elements. The wind in the xy-plane tilts the windward pillar, decreasing two capacitances on the windward side and increasing two capacitances on the leeward side. The wind in the z-axis depresses the windward pillar, resulting in an increase of all four capacitances. Experiments demonstrate that this sensor can measure the wind speed up to 23.9 m/s and the wind direction over the full 360° range of the xy-plane. The sensitivities of wind speed are close to 4 fF·m−1·s and 3 fF·m−1·s in the xy-plane and z-axis, respectively. [ABSTRACT FROM AUTHOR]

In this paper, the wind sensor operating on temperature-balanced mode is investigated. The temperature of four modules is kept as a constant higher than that in the center of the chip. Hence, the wind speed and direction can be characterized by the heating power of the modules. The wind sensor is fabricated on the ceramic substrate, and Ti/Pt is used as heating and sensing resistors. The experiment demonstrates that the power of four modules increases with the wind speed according the King’s law. The total power consumption is about 250 mW@20m/s and 320 mW@40m/s The calibrated results show that the speed varies from 0.2 m/s to 40 m/s with the error of 1 m/s and the direction spans from 0° to 360° with the error of 5°. [ABSTRACT FROM PUBLISHER]

Microfluidic devices in combination with fluorescent microscopy offer high-resolution and high-content platforms to study single-cell morphology, behavior and dynamic process in replicative aging of budding yeast, Saccharomyces cerevisiae . However, a huge mass of recorded images makes the data processing labor-intensive and time-consuming to determine yeast replicative lifespan (RLS), a primary criterion in yeast aging. To address this limitation and pursue label-free RLS assays, electrical impedance spectroscopy (EIS) that can be easily functionalized through microelectrodes in microfluidic devices, was introduced to monitor cell growth and division of budding yeast. Herein, a microfluidic device integrated with EIS biosensor was proposed to perform in-situ impedance measurement of yeast proliferation in single-cell resolution so as to identify the momentary events of daughter dissection from its mother. Single yeast cells were reliably immobilized at the bottleneck-like traps for continuous culturing, during which daughter cells were effectively detached from their mother cells by hydraulic shear forces. Time-lapse impedance measurement was performed every 2 min to monitor the cellular process including budding, division and dissection. By using the K-means clustering algorithm to analyze a self-defined parameter " Dissection Indicator ," to our knowledge for the first time, the momentary event of a daughter removing from its mother cell was accurately extracted from EIS signals. Thus, the identification of daughter dissection events based on impedance sensing technology has been validated. With further development, this microfluidic device integrated with electrical impedance biosensor holds promising applications in high-throughput, real-time and label-free analysis of budding yeast aging and RLS., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Zhu, Geng, Wang, Liu, Yi, Zhao, Ouyang, Zheng, Fan and Wang.)

In this paper, a novel 3D model is proposed to describe the temperature distribution of the thermoelectric microwave power sensor. In this 3D model, the heat flux density decreases from the upper surface to the lower surface of the GaAs substrate while it was supposed to be a constant in the 2D model. The power sensor is fabricated by a GaAs monolithic microwave integrated circuit (MMIC) process and micro-electro-mechanical system (MEMS) technology. The microwave performance experiment shows that the S11 is less than -26 dB over the frequency band of 1-10 GHz. The power response experiment demonstrates that the output voltage increases from 0 mV to 27 mV, while the incident power varies from 1 mW to 100 mW. The measured sensitivity is about 0.27 mV/mW, and the calculated result from the 3D model is 0.28 mV/mW. The relative error has been reduced from 7.5% of the 2D model to 3.7% of the 3D model.

For a two-dimensional solid silicon thermal wind sensor with symmetrical structure, the wind speed and direction information can be derived from the output voltages in two orthogonal directions, i.e., the north-south and east-west. However, the output voltages in these two directions will vary linearly with the ambient temperature. Therefore, in this paper, a temperature model to study the temperature effect on the wind direction measurement has been developed. A theoretical analysis has been presented first, and then Finite Element Method (FEM) simulations have been performed. It is found that due to symmetrical structure of the thermal wind sensor, the temperature effects on the output signals in the north-south and east-west directions are highly similar. As a result, the wind direction measurement of the thermal wind sensor is approximately independent of the ambient temperature. The experimental results fit the theoretical analysis and simulation results very well.