In-situ determination of spin polarization in a single-beam fiber-coupled spin-exchange-relaxation-free atomic magnetometer with differential detection.

The electronic spin polarization of alkali-metal-vapor atoms is a pivotal parameter for atomic magnetometers. Herein, a novel method is presented for determining the spin polarization with a miniaturized single-beam spin-exchange-relaxation-free (SERF) magnetometer on the basis of zero-field cross-over resonance. Two separate laser beams are utilized to heat the cell and interrogate the vapor atoms, respectively. Spin polarization can be extracted by measuring the resonance response signal of the magnetometer to the transverse magnetic field under different irradiances. Results of these experiments are consistent well with the theoretical predictions with the maximum deviation less than 4%. The proposed method has the integrated advantages of possessing a simple configuration and in-situ measurement. Furthermore, combined with a homemade optical differential detection system with a factor of approximately three of the power noise suppression, the developed single-beam SERF atomic magnetometer with a measuring sensitivity of 32 fT/Hz1/2 has been achieved. This demonstrated approach can help guide the development of chip-scale atomic magnetometers for bio-magnetic field imaging applications.

All electrospun fabrics based piezoelectric tactile sensor.

Tactile sensors have been widely used in the areas of health monitoring and intelligent human-machine interface. Flexible tactile sensors based on nanofiber mats made by electrospinning can meet the requirements of comfortability and breathability for wearing the body very well. Here, we developed a flexible and self-powered tactile sensor that was sandwich assembled by electrospun organic electrodes and a piezoelectric layer. The metal-free organic electrodes of thermal plastic polyurethane (PU) nanofibers decorated with multi-walled carbon nanotubes were fabricated by electrospinning followed by ultrasonication treatment. The electrospun polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) mat was utilized as the piezoelectric layer, and it was found that the piezoelectric performance of PVDF-TrFE nanofiber mat added with barium titanate (BaTiO3) nanoparticles was enhanced about 187% than that of the pure PVDF-TrFE nanofiber mat. For practical application, the as-prepared piezoelectric tactile sensor exhibited an approximative linear relationship between the external force and the electrical output. Then the array of fabricated sensors was attached to the fingertips of a glove to grab a cup of water for tactile sensing, and the mass of water can be directly estimated according to the outputs of the sensor array. Attributed to the integrated merits of good flexibility, enhanced piezoelectric performance, light weight, and efficient gas permeability, the developed tactile sensor could be widely used as wearable devices for robot execution end or prosthesis for tactile feedback.

Application and Optimization of Stiffness Abruption Structures for Pressure Sensors with High Sensitivity and Anti-Overload Ability.

The influence of diaphragm bending stiffness distribution on the stress concentration characteristics of a pressure sensing chip had been analyzed and discussed systematically. According to the analysis, a novel peninsula-island-based diaphragm structure was presented and applied to two differenet diaphragm shapes as sensing chips for pressure sensors. By well-designed bending stiffness distribution of the diaphragm, the elastic potential energy induced by diaphragm deformation was concentrated above the gap position, which remarkably increased the sensitivity of the sensing chip. An optimization method and the distribution pattern of the peninsula-island based diaphragm structure were also discussed. Two kinds of sensing chips combined with the peninsula-island structures distributing along the side edge and diagonal directions of rectangular diaphragm were fabricated and analyzed. By bonding the sensing chips with anti-overload glass bases, these two sensing chips were demonstrated by testing to achieve not only high sensitivity, but also good anti-overload ability. The experimental results showed that the proposed structures had the potential to measure ultra-low absolute pressures with high sensitivity and good anti-overload ability in an atmospheric environment.

[The prediction of high-sensitivity C reactive protein for peripheral arterial sclerosis in middle-aged population].

OBJECTIVE: To explore the predictive value of high-sensitivity C reactive protein (hsCRP) in middle-aged population during the peripheral arteriosclerosis. METHODS: Random sampling method was used in the study. In 2006-2007 Kailuan Group health examination of 101,510 employees, using stratified random sampling method to select 5,852 as observational cohort included, in the final with a standard queue 5,440 in December 2009. This study selected to participate in the 2012-2013 health examination cohort as the research object, in accordance with the inclusion criteria ultimately selected survey 3,978, select the epidemiological investigation, physical examination, laboratory testing data analysis. Of the 3 978 subjects, 2,282 were male and 1,696 were female, and the baseline age was (53.80±11.14) years. According to the baseline hsCRP quartile level was divided into four groups for comparison of baseline data, using multiple linear regression analysis between hsCRP and brachial-ankle pulse wave velocity (baPWV). Area under the receiver operating characteristic (ROC) curve (AUC) was used to evaluate the prediction of hsCRP levels in peripheral arteriosclerosis. RESULTS: With increase of hsCRP levels, the survey of baseline levels of baPWV showed increasing trend, (1,445.49±300.55), (1,494.46±307.94), (1,547.67±320.34), (1,621.32±342.53) cm/s, respectively. Multiple linear regression results showed that age, by logarithmic transformation of hsCRP (lghsCRP) level, systolic blood pressure and fasting blood glucose for each additional unit, baPWV levels were increased 266.47, 58.00, 5.02, 39.79 cm/s (P<0.001), and BMI for each additional unit, baPWV level decreased 9.52 cm/s (P=0.030). The prediction of hsCRP in peripheral artery showed that lghsCRP level of AUC to 0.59 (95% CI: 0.57-0.61), lower than the age and systolic blood pressure predicted value AUC (95% CI) of 0.69 (0.67-0.71), 0.75 (0.73-0.77), respectively. CONCLUSION: The hsCRP level could not predict the peripheral arteriosclerosis alone, and the combined age and systolic blood pressure level could have better predictive value.

Monolithically integrated triaxial high-performance micro accelerometers with position-independent pure axial stressed piezoresistive beams.

With the increasing demand for multidirectional vibration measurements, traditional triaxial accelerometers cannot achieve vibration measurements with high sensitivity, high natural frequency, and low cross-sensitivity simultaneously. Moreover, for piezoresistive accelerometers, achieving pure axial deformation of the piezoresistive beam can greatly improve performance, but it requires the piezoresistive beam to be located in a specific position, which inevitably makes the design more complex and limits the performance improvement. Here, a monolithically integrated triaxial high-performance accelerometer with pure axial stress piezoresistive beams was designed, fabricated, and tested. By controlling synchronous displacements at both piezoresistive beam ends, the pure axial stress states of the piezoresistive beams could be easily achieved with position independence without tedious calculations. The measurement unit for the z-axis acceleration was innovatively designed as an interlocking proof mass structure to ensure a full Wheatstone bridge for sensitivity improvement. The pure axial stress state of the piezoresistive beams and low cross-sensitivity of all three units were verified by the finite element method (FEM). The triaxial accelerometer was fabricated and tested. Results showing extremely high sensitivities (x axis: 2.43 mV/g/5 V; y axis: 2.44 mv/g/5 V; z axis: 2.41 mV/g/5 V (without amplification by signal conditioning circuit)) and high natural frequencies (x/y axes: 11.4 kHz; z-axis: 13.2 kHz) were obtained. The approach of this paper makes it simple to design and obtain high-performance piezoresistive accelerometers.

Investigation on the Effect of Annealing Temperature on the Side Ohmic Contact Characteristics for Double Channel GaN/AlGaN Epitaxial Layer.

A side ohmic contact mode for the double channel GaN/AlGaN epitaxial layer is proposed in this paper. Rectangle transmission line model (TLM) electrodes are prepared, and the specific contact resistance is tested at the annealing temperatures from 700 °C to 850 °C. The results show that the minimum specific contact resistance is 2.58 × 10-7 Ω·cm2 at the annealing temperature of 750 °C, which is three to four times lower than the surface contact mode. Scanning electron microscope (SEM), energy dispersive spectrometer (EDS), and atomic force microscope (AFM) were carried out for the analysis of the morphology, element composition, and the height fluctuation at the contact edge. With the increase in the annealing temperature, the specific contact resistance decreases due to the alloying of electrodes and the raised number of N vacancies. However, when the annealing temperature exceeds 800 °C, the state of the stress in the electrode films transforms from compressive stress to tensile stress. Besides, the volume expansion of metal electrode film and the increase in the roughness at the contact edge leads to the degradation of the side ohmic contact characteristics.

A Flexible and Wearable Nylon Fiber Sensor Modified by Reduced Graphene Oxide and ZnO Quantum Dots for Wide-Range NO2 Gas Detection at Room Temperature.

Reduced graphene oxide (rGO) fiber as a carbon-based fiber sensor has aroused widespread interest in the field of gas sensing. However, the low response value and poor flexibility of the rGO fiber sensor severely limit its application in the field of flexible wearable electronics. In this paper, a flexible and wearable nylon fiber sensor modified by rGO and ZnO quantum dots (QDs) is proposed for wide-range NO2 gas detection at room temperature. The response value of the nylon fiber sensor to 100 ppm NO2 gas is as high as 0.4958, and the response time and recovery time are 216.2 s and 667.9 s, respectively. The relationship between the sensor's response value and the NO2 concentration value is linear in the range of 20-100 ppm, and the fitting coefficient is 0.998. In addition, the test results show that the sensor also has good repeatability, flexibility, and selectivity. Moreover, an early warning module was also designed and is proposed in this paper to realize the over-limit monitoring of NO2 gas, and the flexible sensor was embedded in a mask, demonstrating its great application potential and value in the field of wearable electronics.

Piezoelectric-AlN resonators at two-dimensional flexural modes for the density and viscosity decoupled determination of liquids.

A micromachined resonator immersed in liquid provides valuable resonance parameters for determining the fluidic parameters. However, the liquid operating environment poses a challenge to maintaining a fine sensing performance, particularly through electrical characterization. This paper presents a piezoelectric micromachined cantilever with a stepped shape for liquid monitoring purposes. Multiple modes of the proposed cantilever are available with full electrical characterization for realizing self-actuated and self-sensing capabilities. The focus is on higher flexural resonances, which nonconventionally feature two-dimensional vibration modes. Modal analyses are conducted for the developed cantilever under flexural vibrations at different orders. Modeling explains not only the basic length-dominant mode but also higher modes that simultaneously depend on the length and width of the cantilever. This study determines that the analytical predictions for resonant frequency in liquid media exhibit good agreement with the experimental results. Furthermore, the experiments on cantilever resonators are performed in various test liquids, demonstrating that higher-order flexural modes allow for the decoupled measurements of density and viscosity. The measurement differences achieve 0.39% in density and 3.50% in viscosity, and the frequency instability is below 0.05‰. On the basis of these results, design guidelines for piezoelectric higher-mode resonators are proposed for liquid sensing.

Novel high-performance piezoresistive shock accelerometer for ultra-high-g measurement utilizing self-support sensing beams.

This study describes the design and implementation of a novel high-performance piezoresistive accelerometer for the measurement of shock acceleration of up to 100 000 g. The structure of the accelerometer sensing chip was implemented with piezoresistive self-support beams. The piezoresistors were made in piezoresistive sensing micro-beams, which were independent of support beams, to weaken the correlation between measuring sensitivity and resonant frequency. In this way, the measuring sensitivity of the proposed novel piezoresistive accelerometer could be increased without sacrificing resonant frequency. The optimization of structural dimensions of the sensing chip was conducted through finite element method simulations. The sensing chip was fabricated employing bulk-micromachining technology with a silicon-on-insulator wafer. The fabricated accelerometer was encapsulated in stainless shell and evaluated using the Hopkinson bar system. Results demonstrated the proposed accelerometer with the measuring sensitivity of 0.54 µV/g/V and the resonant frequency of 445 kHz.

WRe26-In2O3 probe-type thin film thermocouples applied to high temperature measurement.

A novel probe-type thin film thermocouple has been fabricated successfully for high temperature measurement applications. WRe26 (tungsten-26% rhenium)-In2O3 thermoelectric materials were used in the thermocouples to achieve high thermoelectric output and high temperature resistance. The films were deposited on a cylindrical substrate by magnetron sputtering technology. The annealing process of the thermocouples was studied to achieve optimal performance. The calibration results showed the thermoelectric output of WRe26-In2O3 thin film thermocouples reached 93.7 mv at 700 °C, and its sensitivity was 165.5 µV/°C under the temperature of the cold junction, which was 133.8 °C. The thermocouples developed in this work have great potential for practical applications.

Effect of Annealing on the Thermoelectricity Properties of the WRe26-In2O3 Thin Film Thermocouples.

WRe26-In2O3 (WRe26 (tungsten-26% rhenium) and In2O3 thermoelectric materials) thin film thermocouples (TFTCs) have been fabricated based on magnetron sputtering technology, which can be used in temperature measurement. Many annealing processes were studied to promote the sensitivity of WRe26-In2O3 TFTCs. The optimal annealing process of the thermocouple under this kind of RF magnetron sputtering method was proposed after analyzing the properties of In2O3 films and the thermoelectric voltage of TFTCs at different annealing processes. The calibration results showed that the WRe26-In2O3 TFTCs achieved a thermoelectric voltage of 123.6 mV at a temperature difference of 612.9 K, with a sensitivity of up to 201.6 µV/K. Also, TFTC kept a stable thermoelectric voltage output at 973 K for 20 min and at 773 K for two hours. In general, the WRe26-In2O3 TFTCs developed in this work have great potential for practical applications. In future work, we will focus on the thermoelectric stability of TFTCs at higher temperatures.

Novel resonant pressure sensor based on piezoresistive detection and symmetrical in-plane mode vibration.

In this paper, a novel resonant pressure sensor is developed based on electrostatic excitation and piezoresistive detection. The measured pressure applied to the diaphragm will cause the resonant frequency shift of the resonator. The working mode stress-frequency theory of a double-ended tuning fork with an enhanced coupling beam is proposed, which is compatible with the simulation and experiment. A unique piezoresistive detection method based on small axially deformed beams with a resonant status is proposed, and other adjacent mode outputs are easily shielded. According to the structure design, high-vacuum wafer-level packaging with different doping in the anodic bonding interface is fabricated to ensure the high quality of the resonator. The pressure sensor chip is fabricated by dry/wet etching, high-temperature silicon bonding, ion implantation, and wafer-level anodic bonding. The results show that the fabricated sensor has a measuring sensitivity of ~19 Hz/kPa and a nonlinearity of 0.02% full scale in the pressure range of 0-200 kPa at a full temperature range of -40 to 80 °C. The sensor also shows a good quality factor >25,000, which demonstrates the good vacuum performance. Thus, the feasibility of the design is a commendable solution for high-accuracy pressure measurements.

Temperature compensation in fluid density measurement using micro-electromechanical resonant sensor.

In order to improve the measuring accuracy of micro-electromechanical system (MEMS) resonant sensor with micro-cantilever structure to measure fluid density, a temperature compensation method is presented. The elastic modulus of the micro-cantilever is calculated considering its temperature coefficient so that the working equation to measure fluid density is obtained with decreasing temperature disturbance on the measuring accuracy. The simulations and experimental measurements of several fluids with different densities were carried out by the MEMS micro-cantilever resonant sensor under different temperatures. The simulation analyses showed that the fluid densities measured by using the proposed resonant density sensor with temperature compensation were more fitted with the reference density values than those without temperature compensation. The experimental results showed that both the measuring accuracy and stability of the MEMS micro-cantilever resonant sensor in fluid density measurement were increased more than twice based on the temperature compensation method. Therefore, the proposed temperature compensation method is important to improve the measuring precision and stability of the MEMS micro-cantilever resonant sensor in fluid density detection fields.