Microelectromechanical Sensors Research Articles

Noise of a JFET Charge Amplifier for Piezoelectric Sensors

A comprehensive noise model of a junction gate field-effect transistor (JFET) charge amplifier is presented for applications with piezoelectric sensors. Based on this previously reported amplifier structure, a noise equivalent circuit is derived and discussed. Universal noise gain expressions for each of the twelve considered noise sources are given. By means of an analytical description of the charge amplifier’s noise behavior, the design and optimization of such preamplifiers for various capacitive microelectromechanical sensor systems will be distinctly simplified. Calculations of the noise floor are compared with measurements with a cantilever-type magnetoelectric sensor and with the performance of a so far commonly utilized basic charge amplifier. With the JFET charge amplifier a noise reduction of approximately 22 dB is achieved in the vicinity of the utilized sensor’s resonance frequency of 7.45 kHz. The reported amplifier is the first which has no negative influence on the total noise level of a resonant magnetoelectric sensor system.

Non-contact rolling surface wave measurements on asphalt concrete

Rolling surface wave measurements on a single, thin asphalt concrete (AC) layer are presented to investigate their use in rapid nondestructive field tests. An array of 47 micro-electro-mechanical sensor (MEMS) microphones is mounted on a trailer together with an automated impact source. Multichannel recordings from single impacts are obtained at 80 equally spaced array positions as the trailer moves at a constant speed. The complete battery-powered data acquisition system enables large-scale testing of newly built pavements. Multiple sets of test results show good repeatability for the assessed shear wave velocity and demonstrate the strong temperature dependency of AC. The presented results indicate a possible application for quality assurance of AC using rolling surface wave measurements.

Thermoresistive Effect for Advanced Thermal Sensors: Fundamentals, Design Considerations, and Applications

Microelectromechanical systems sensors have been intensively developed utilizing various physical concepts, such as piezoresistive, piezoelectric, and thermoresistive effects. Among these sensing concepts, the thermoresistive effect is of interest for a wide range of thermal sensors and devices, thanks to its simplicity in implementation and high sensitivity. The effect of temperature on the electrical resistance of some metals and semiconductors has been thoroughly investigated, leading to the significant growth and successful demonstration of thermal-based sensors, such as temperature sensors, convective accelerometers and gyroscopes, and thermal flow sensors. In this paper, we review the fundamentals of the thermoresistive effect in metals and semiconductors. We also discuss the influence of design and fabrication parameters on the thermoresistive sensitivity. This paper includes several desirable features of thermoresistive sensors and recent developments in these sensors are summarized. This review provides insights into how it is affected by various parameters, and useful guidance for industrial designers in terms of high sensitivity and linearity and fast response. [2017-0022]

Fish-inspired self-powered microelectromechanical flow sensor with biomimetic hydrogel cupula

Flow sensors inspired from lateral line neuromasts of cavefish have been widely investigated over decades to develop artificial sensors. The design and function of these natural sensors have been mimicked using microelectromechanical systems (MEMS) based sensors. However, there is more to the overall function and performance of these natural sensors. Mimicking the morphology and material properties of specialized structures like a cupula would significantly help to improve the existing designs. Toward this goal, the paper reports development of a canal neuromast inspired piezoelectric sensor and investigates the role of a biomimetic cupula in influencing the performance of the sensor. The sensor was developed using microfabrication technology and tested for the detection of the steady-state and oscillatory flows. An artificial cupula was synthesized using a soft hydrogel material and characterized for morphology and mechanical properties. Results show that the artificial cupula had a porous structure and high mechanical strength similar to the biological canal neuromast. Experimental results show the ability of these sensors to measure the steady-state flows accurately, and for oscillatory flows, an increase in the sensor output was detected in the presence of the cupula structure. This is the first time a MEMS based piezoelectric sensor is demonstrated to detect steady-state flows using the principle of vortex-induced vibrations. The bioinspired sensor developed in this work would be investigated further to understand the role of the cupula structure in biological flow sensing mechanisms, thus contributing toward the design of highly sensitive and efficient sensors for various applications such as underwater robotics, microfluidics, and biomedical devices.

Which Method Detects Foot Strike in Rearfoot and Forefoot Runners Accurately when Using an Inertial Measurement Unit?

Accelerometers and gyroscopes are used to detect foot strike (FS), i.e., the moment when the foot first touches the ground. However, it is unclear whether different conditions (footwear hardness or foot strike pattern) influence the accuracy and precision of different FS detection methods when using such micro-electromechanical sensors (MEMS). This study compared the accuracy of four published MEMS-based FS detection methods with each other and the gold standard (force plate) to establish the most accurate method with regard to different foot strike patterns and footwear conditions. Twenty-three recreational runners (12 rearfoot and 11 forefoot strikers) ran on a 15-m indoor track at their individual running speed in three footwear conditions (low to high hardness). MEMS and a force plate were sampled at a rate of 3750 Hz. Individual accuracy and precision of FS detection methods were found which were dependent on running styles and footwear conditions. Most of the methods were characterized by a delay which generally increased from rearfoot to forefoot strike pattern and from high to low midsole hardness. It can be concluded that only one of the four methods can accurately determine FS in a variety of conditions.

Application of Surface Protective Coating to Enhance Environment-Withstanding Property of the MEMS 2D Wind Direction and Wind Speed Sensor.

In this study, a microelectromechanical system (MEMS) two-dimensional (2D) wind direction and wind speed sensor consisting of a square heating source and four thermopiles was manufactured using the heat detection method. The heating source and thermopiles of the manufactured sensor must be exposed to air to detect wind speed and wind direction. Therefore, there are concerns that the sensor could be contaminated by deposition or adhesion of dust, sandy dust, snow, rain, and so forth, in the air, and that the membrane may be damaged by physical shock. Hence, there was a need to protect the heating source, thermopiles, and the membrane from environmental and physical shock. The upper protective coating to protect both the heating source and thermopiles and the lower protective coating to protect the membrane were formed by using high-molecular substances such as SU-8, Teflon and polyimide (PI). The sensor characteristics with the applied protective coatings were evaluated.

Left Atrial Pressure Monitoring With an Implantable Wireless Pressure Sensor After Implantation of a Left Ventricular Assist Device.

After implantation of a continuous-flow left ventricular assist device (LVAD), left atrial pressure (LAP) monitoring allows for the precise management of intravascular volume, inotropic therapy, and pump speed. In this case series of 4 LVAD recipients, we report the first clinical use of this wireless pressure sensor for the long-term monitoring of LAP during LVAD support. A wireless microelectromechanical system pressure sensor (Titan, ISS Inc., Ypsilanti, MI) was placed in the left atrium in four patients at the time of LVAD implantation. Titan sensor LAP was measured in all four patients on the intensive care unit and in three patients at home. Ramped speed tests were performed using LAP and echocardiography in three patients. The left ventricular end-diastolic diameter (cm), flow (L/min), power consumption (W), and blood pressure (mm Hg) were measured at each step. Measurements were performed over 36, 84, 137, and 180 days, respectively. The three discharged patients had equipment at home and were able to perform daily recordings. There were significant correlations between sensor pressure and pump speed, LV and LA size and pulmonary capillary wedge pressure, respectively (r = 0.92–0.99, p < 0.05). There was no device failure, and there were no adverse consequences of its use.

Real-Time Electrical Bioimpedance Characterization of Neointimal Tissue for Stent Applications.

To follow up the restenosis in arteries stented during an angioplasty is an important current clinical problem. A new approach to monitor the growth of neointimal tissue inside the stent is proposed on the basis of electrical impedance spectroscopy (EIS) sensors and the oscillation-based test (OBT) circuit technique. A mathematical model was developed to analytically describe the histological composition of the neointima, employing its conductivity and permittivity data. The bioimpedance model was validated against a finite element analysis (FEA) using COMSOL Multiphysics software. A satisfactory correlation between the analytical model and FEA simulation was achieved in most cases, detecting some deviations introduced by the thin “double layer” that separates the neointima and the blood. It is hereby shown how to apply conformal transformations to obtain bioimpedance electrical models for stack-layered tissues over coplanar electrodes. Particularly, this can be applied to characterize the neointima in real-time. This technique is either suitable as a main mechanism for restenosis follow-up or it can be combined with proposed intelligent stents for blood pressure measurements to auto-calibrate the sensibility loss caused by the adherence of the tissue on the micro-electro-mechanical sensors (MEMSs).

Piezoresistive pressure sensor with high sensitivity for medical application using peninsula-island structure

A novel micro-electromechanical systems piezoresistive pressure sensor with a diagonally positioned peninsula-island structure has high sensitivity for ultralow- pressure measurement. The pressure sensor was designed with a working range of 0–500 Pa and had a high sensitivity of 0.06 mV·V–1·Pa–1. The trade-off between high sensitivity and linearity was alleviated. Moreover, the influence of the installation angle on the sensing chip output was analyzed, and an application experiment of the sensor was conducted using the built pipettor test platform. Findings indicated that the proposed pressure sensor had sufficient resolution ability and accuracy to detect the pressure variation in the pipettor chamber. Therefore, the proposed pressure sensor has strong potential for medical equipment application.

Investigation of the influence of double-sided diaphragm on performance of capacitance and sensitivity of touch mode capacitive pressure sensor: numerical modeling and simulation forecasting

Microelectromechanical system-based capacitive pressure sensors have seen significant advancements in modeling and design. This paper provides a complete analysis of a novel improvement to existing models of the touch mode capacitive pressure sensor. An in-depth, step-by-step derivation of the capacitance, capacitive sensitivity and mechanical sensitivity is examined for the double-sided touch mode capacitive pressure sensor. The results generated are modeled and examined using MATLAB. Comparisons with previous models clearly delineate the improved performance in terms of capacitance and sensitivity. The analysis conducted dovetail perfectly with the modeled results.

To design better hardware, think like a cyber-criminal [Resources_At Work

The future of cybersecurity is in the hands of hardware engineers, says Scott Borg, director of the U.S. Cyber Consequences Unit, a nonprofit think tank based in Vermont. He spoke in May at the MEMS & Sensors Technical Congress, held at Stanford University, in California, to an audience of 130 chief technical officers, engineering directors, and key researchers from microelectromechanical systems and sensors companies and labs. Borg warned that “the people in this room are now moving into the crosshairs of cyberhackers in a way that has never happened before.”

Algorithm for navigation of ground-based transport-technological facilities on the basis of integrated inertial-satellite navigation and odometer data

The dynamic development of navigation technologies has led to the emergence of practical applications for the solution of the problem of navigation of ground transport and technological facilities (GTTF). The most promising way of solving the navigation problem of GTTF is the creation of integrated inertial-satellite navigation systems. For a long period of time, the widespread use of navigation systems for transport applications was constrained by their high cost. The appearance of low-cost microelectromechanical (MEMS) inertial sensors on the market of navigation equipment provided the technological basis for the creation of small-scale inertial-satellite navigation systems. For transport applications, integrated inertial-satellite are integrated with additional information sensors, which include the odometer. Implementation of integrated systems is impeded by massively high level of intrinsic errors in MEMS sensors, as well as by the low accuracy of determining navigational parameters in the zone where the satellite signal of the satellite navigation systems is not stable. It is obvious that the development of methods for processing measurement information and the synthesis of specialized algorithms that ensure the accuracy of navigation systems GTTF is an urgent scientific task. In this paper, a schematic and technical solution for constructing an integrated inertial-satellite navigation systems with an integrated odometer sensor is presented and justified. A specialized navigation algorithm is developed that provides an integrated navigation solution for data coming from heterogeneous sources of measurements. A detailed functional diagram of the algorithm is given. A set of functional criteria for the quality and reliability of the navigation solution is defined. Correction algorithms for the main kinematic parameters of the trajectory motion of the GTTF - the true course angle, the location coordinates, the velocity vector components, are developed. The developed algorithm is invariant to the type of inertial sensors and in this sense is unified. Performance was confirmed by the results of full-scale tests of the navigation system of a forklift truck carrying out freight traffic on the territory of the seaport.

An Optical MEMS Accelerometer Based on a Two-Dimensional Photonic Crystal Add-Drop Filter

In this paper, a novel optical microelectromechanical systems accelerometer sensor is proposed by using a two-dimensional photonic crystal add-drop filter which is relied on a wavelength modulation approach. The proposed optical sensing system consists of a laser diode light source, tunable add-drop filter based on ring resonator principal, photo-detector, and integrated waveguides. Simulation results show that the functional characteristics of the proposed sensor are as follows: mechanical sensitivity of 1.6 nm/g, linear measurement range of $-$ 156 to 156 g, optical sensitivity of 0.0756 nm/g, and first resonance frequency of 12.9 kHz. These functional characteristics make it very interesting in a wide spectrum of applications, ranging from consumer electronics to automotive and inertial navigation.

Differential capacitive pressure sensor design based on standard CMOS

A microelectromechanical system capacitive pressure sensor with a differential configuration (patent pending), including a reference and sensitive capacitor, is presented. A single cavity includes both reference and sensitive electrodes. This implementation is achieved by a size reduction of the sensitive electrode. A reduction of the 40% on the sensible electrode area represents a decrease in the sensor sensitivity of only 12.5%, and allows the reference capacitor implementation in the area commonly used only for the sensitive capacitor. A tridimensional model of the sensor was simulated using a finite-element solver considering coupled mechanical and electrostatic models. The simulations show that this pressure sensor has a sensitivity of 4.2 fF/bar. The proposed pressure sensor designs use only materials available in complementary metal oxide silicon (CMOS) standard processes. A CMOS compatible post-process, based on the sacrificial material technique and its restrictions is presented.

INS/GNSS Integration for Aerobatic Flight Applications and Aircraft Motion Surveying.

This paper presents field tests of challenging flight applications obtained with a new family of lightweight low-power INS/GNSS (inertial navigation system/global satellite navigation system) solutions based on MEMS (micro-electro-mechanical- sensor) machined sensors, being used for UAV (unmanned aerial vehicle) navigation and control as well as for aircraft motion dynamics analysis and trajectory surveying. One key is a 42+ state extended Kalman-filter-based powerful data fusion, which also allows the estimation and correction of parameters that are typically affected by sensor aging, especially when applying MEMS-based inertial sensors, and which is not yet deeply considered in the literature. The paper presents the general system architecture, which allows iMAR Navigation the integration of all classes of inertial sensors and GNSS (global navigation satellite system) receivers from very-low-cost MEMS and high performance MEMS over FOG (fiber optical gyro) and RLG (ring laser gyro) up to HRG (hemispherical resonator gyro) technology, and presents detailed flight test results obtained under extreme flight conditions. As a real-world example, the aerobatic maneuvers of the World Champion 2016 (Red Bull Air Race) are presented. Short consideration is also given to surveying applications, where the ultimate performance of the same data fusion, but applied on gravimetric surveying, is discussed.

One-batch transfer process for the additive manufacturing of a cantilever with a weight

An improved transferring process that can be used to additively fabricate a cantilever with a weight is reported. By using a poly(dimethylsiloxane) template with a cavity relief structure for the weight formation, an increase in the number of process steps was not required. A capacitive acceleration sensor was successfully manufactured using the described process. Enhanced responsiveness of the sensor was clearly shown to result from the effect of the weight. The one-batch transfer process has the potential to significantly simplify the manufacturing process of highly responsive hollow structures and could be applied in the fabrication of various microelectromechanical system sensors.

A study on thermo-mechanical behavior of MCD through bulge test analysis

The Micro circular diaphragm (MCD) is the mechanical actuator part used in the micro electro-mechanical sensors (MEMS) that combine electrical and mechanical components. These actuators are working under harsh mechanical and thermal conditions, so it is very important to study the mechanical and thermal behaviors of these actuators, in order to do with its function successfully. The objective of this paper is to determine the thermo-mechanical behavior of MCD by developing the traditional bulge test technique to achieve the aims of this work. The specimen is first pre-stressed to ensure that is no initial deflection before applied the loads on diaphragm and then clamped between two plates, a differential pressure (P) and temperature (Tb) is leading to a deformation of the MCD. Analytical formulation of developed bulge test technique for MCD thermo-mechanical characterization was established with taking in-to account effect of the residual strength from pre-stressed loading. These makes the plane-strain bulge test ideal for studying the mechanical and thermal behavior of diaphragm in both the elastic and plastic regimes. The differential specimen thickness due to bulge effect to describe the mechanical behavior, and the temperature effect on the MCD material properties to study the thermal behavior under deformation were discussed. A finite element model (FEM) can be extended to apply for investigating the reliability of the proposed bulge test of MCD and compare between the FEM results and another one from analytical calculus. The results show that, the good convergence between the finite element model and analytical model.

Use of the Magnetic Field for Improving Gyroscopes' Biases Estimation.

An accurate orientation is crucial to a satisfactory position in pedestrian navigation. The orientation estimation, however, is greatly affected by errors like the biases of gyroscopes. In order to minimize the error in the orientation, the biases of gyroscopes must be estimated and subtracted. In the state of the art it has been proposed, but not proved, that the estimation of the biases can be accomplished using magnetic field measurements. The objective of this work is to evaluate the effectiveness of using magnetic field measurements to estimate the biases of medium-cost micro-electromechanical sensors (MEMS) gyroscopes. We carry out the evaluation with experiments that cover both, quasi-error-free turn rate and magnetic measurements and medium-cost MEMS turn rate and magnetic measurements. The impact of different homogeneous magnetic field distributions and magnetically perturbed environments is analyzed. Additionally, the effect of the successful biases subtraction on the orientation and the estimated trajectory is detailed. Our results show that the use of magnetic field measurements is beneficial to the correct biases estimation. Further, we show that different magnetic field distributions affect differently the biases estimation process. Moreover, the biases are likewise correctly estimated under perturbed magnetic fields. However, for indoor and urban scenarios the biases estimation process is very slow.

Cross-Linked Gold-Nanoparticle Membrane Resonators as Microelectromechanical Vapor Sensors.

We report a novel approach for the detection of volatile compounds employing electrostatically driven drumhead resonators as sensing elements. The resonators are based on freestanding membranes of alkanedithiol cross-linked gold nanoparticles (GNPs), which are able to sorb analytes from the gas phase. Under reduced pressure, the fundamental resonance frequency of a resonator is continuously monitored while the device is exposed to varying partial pressures of toluene, 4-methylpentan-2-one, 1-propanol, and water. The measurements reveal a strong, reversible frequency shift of up to ∼10 kHz, i.e., ∼5% of the fundamental resonance frequency, when exposing the sensor to toluene vapor with a partial pressure of ∼20 Pa. As this strong shift cannot be explained exclusively by the mass uptake in the membrane, our results suggest a significant impact of analyte sorption on the pre-stress of the freestanding GNP membrane. Thus, our findings point to the possibility of designing highly sensitive resonators, which utilize sorption induced changes in the membrane's pre-stress as primary transduction mechanism.

A Low-Cost Lane-Determination System Using GNSS/IMU Fusion and HMM-Based Multistage Map Matching

This paper presents a low-cost real-time lane-determination system that fuses micro-electromechanical systems inertial sensors (accelerometers and gyroscopes), global navigation satellite system (GNSS), and commercially available road network maps. The system can be used for intelligent transportation systems, telematics applications, and autonomous driving. The system does not depend on visual markings or highly precise GNSS technology, such as DGPS or RTK, and it does not need explicit lane-level resolution maps. High-resolution estimation of the vehicle’s position, velocity, and orientation is implemented by fusing inertial sensors with GNSS in a loosely coupled mode using extended Kalman filter. A curve-to-curve road-level map-matching is implemented using a hidden Markov model followed by a least-square regression step that estimates the vehicle’s lane. The system includes a lane-change detector based on inertial sensors and the filtered vehicle’s state. The system has been realized in real time and tested extensively on real-road data. Experiments showed robust map-matching in challenging road intersections and a 97.14% lane-determination success rate.