A novel method of temperature compensation for piezoresistive microcantilever-based sensors

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.

A Real-Time Thermal Self-Elimination Method for Static Mode Operated Freestanding Piezoresistive Microcantilever-Based Biosensors

Here, we provide a method and apparatus for real-time compensation of the thermal effect of single free-standing piezoresistive microcantilever-based biosensors. The sensor chip contained an on-chip fixed piezoresistor that served as a temperature sensor, and a multilayer microcantilever with an embedded piezoresistor served as a biomolecular sensor. This method employed the calibrated relationship between the resistance and the temperature of piezoresistors to eliminate the thermal effect on the sensor, including the temperature coefficient of resistance (TCR) and bimorph effect. From experimental results, the method was verified to reduce the signal of thermal effect from 25.6 μV/°C to 0.3 μV/°C, which was approximately two orders of magnitude less than that before the processing of the thermal elimination method. Furthermore, the proposed approach and system successfully demonstrated its effective real-time thermal self-elimination on biomolecular detection without any thermostat device to control the environmental temperature. This method realizes the miniaturization of an overall measurement system of the sensor, which can be used to develop portable medical devices and microarray analysis platforms.

Annularly grooved membrane combined with rood beam piezoresistive pressure sensor for low pressure applications

A novel structural piezoresistive pressure sensor with annularly grooved membrane combined with rood beam has been proposed for low pressure measurements based on silicon substrate. In this study, a design method, including the model design, dimensions optimization, and performance prediction of the novel structure sensor, is presented. The finite element method has been used to analyze the stress distribution of sensitive elements and the deflection of membrane. On the basis of simulation results, the relationships between structural dimension variables and mechanical performance are deduced, which make the fabrication processes more efficient. According to statistics theory, the coefficient of determination R² and residual sum of squares are introduced to indicate whether the fitting equations and curves match well with the simulation results. After that, a series of the optimal membrane dimensions are determined. Compared with other structural sensors, the optimized sensor achieves the best overall properties as it mitigates the contradiction between sensitivity and linearity. The reasons why the proposed sensor can maximize sensitivity and minimize nonlinearity are also discussed. By localizing more strain energy in the high concentrated stress profile and creating partially stiffened membrane, the proposed sensor has achieved a high sensitivity of 34.5 (mV/V)/psi and a low nonlinearity of 0.25% FSS. Thus, the proposed structure sensor will be a proper choice for low pressure applications less than 1 psi.

Thermal-Performance Instability in Piezoresistive Sensors: Inducement and Improvement

The field of piezoresistive sensors has been undergoing a significant revolution in terms of design methodology, material technology and micromachining process. However, the temperature dependence of sensor characteristics remains a hurdle to cross. This review focuses on the issues in thermal-performance instability of piezoresistive sensors. Based on the operation fundamental, inducements to the instability are investigated in detail and correspondingly available ameliorative methods are presented. Pros and cons of each improvement approach are also summarized. Though several schemes have been proposed and put into reality with favorable achievements, the schemes featuring simple implementation and excellent compatibility with existing techniques are still emergently demanded to construct a piezoresistive sensor with excellent comprehensive performance.

An improved algorithm of temperature compensation for a near infrared multiple-acquisition system based on two-dimensional regression analysis

The near infrared (NIR) spectroscopy analytical technique is one of the most advanced and promising tools in many domains. NIR acquisition is easily influenced by temperature, thereby affecting qualitative and quantitative analyses. In this paper, a temperature compensation model was established between NIR signals and output voltage values based on two-dimensional regression analysis. The effectiveness of the proposed compensation scheme was experimentally demonstrated by the measurement of six super luminescent diode sources at 293-313 K. The coefficient of variation was decreased 2-fold with this compensation algorithm. The results indicated that it was suitable for various NIR spectral acquisition systems with lower complexity and a higher signal-noise-ratio after being applied to an acousto-optic-tunable-filter system.

Polypyrrole/silver coaxial nanowire aero-sponges for temperature-independent stress sensing and stress-triggered Joule heating

To obtain ideal sensing materials with nearly zero temperature coefficient resistance (TCR) for self-temperature-compensated pressure sensors, we proposed an Incipient Network Conformal Growth (INCG) technology to prepare hybrid and elastic porous materials: the nanoparticles (NPs) are first dispersed in solvent to form an incipient network, another component is then introduced to coat the incipient network conformally via wet chemical route. The conformal coatings not only endow NPs with high stability but also offer them additional structural elasticity, meeting requirements for future generations of portable, compressive and flexible devices. The resultant polypyrrole/silver coaxial nanowire hybrid aero-sponges prepared via INCG technology have been processed into a piezoresistive sensor with highly sensing stability (low TCR 0.86 × 10(-3)/°C), sensitivity (0.33 kPa(-1)), short response time (1 ms), minimum detectable pressure (4.93 Pa) after suffering repeated stimuli, temperature change and electric heating. Moreover, a stress-triggered Joule heater can be also fabricated mainly by the PPy-Ag NW hybrid aero-sponges with nearly zero temperature coefficient.

A novel optimal sensitivity design scheme for yarn tension sensor using surface acoustic wave device

In this paper, we propose a novel optimal sensitivity design scheme for the yarn tension sensor using surface acoustic wave (SAW) device. In order to obtain the best sensitivity, the regression model between the size of the SAW yarn tension sensor substrate and the sensitivity of the SAW yarn tension sensor was established using the least square method. The model was validated too. Through analyzing the correspondence between the regression function monotonicity and its partial derivative sign, the effect of the SAW yarn tension sensor substrate size on the sensitivity of the SAW yarn tension sensor was investigated. Based on the regression model, a linear programming model was established to gain the optimal sensitivity of the SAW yarn tension sensor. The linear programming result shows that the maximum sensitivity will be achieved when the SAW yarn tension sensor substrate length is equal to 15 mm and its width is equal to 3mm within a fixed interval of the substrate size. An experiment of SAW yarn tension sensor about 15 mm long and 3mm wide was presented. Experimental results show that the maximum sensitivity 1982.39 Hz/g was accomplished, which confirms that the optimal sensitivity design scheme is useful and effective.

A Passive Radio-Frequency Identification (RFID) Gas Sensor With Self-Correction Against Fluctuations of Ambient Temperature

Uncontrolled fluctuations of ambient temperature in the field typically greatly reduce accuracy of gas sensors. In this study, we developed an approach for the self-correction against fluctuations of ambient temperature of individual gas and vapor sensors. The main innovation of our work is in the temperature correction which is accomplished without the need for a separate uncoated reference sensor or a separate temperature sensor. Our sensors are resonant inductor-capacitor-resistor (LCR) transducers coated with sensing materials and operated as multivariable passive (battery-free) radio-frequency identification (RFID) sensors. Using our developed approach, we performed quantitation of an exemplary vapor over the temperature range from 25 to 40 °C. This technical solution will be attractive in numerous applications where temperature stabilization of a gas sensor or addition of auxiliary temperature or uncoated reference sensors is prohibitive.