Mass Sensor Research Articles

A High Frequency Dual Inverted Mesa QCM Sensor Array with Concentric Electrodes

Quartz Crystal Microbalance (QCM) is a candidate technology for high sensitivity application. This mass sensor's property depends on the piezoelectric property of the AT-cut quartz crystal. QCM has been widely employed for gas detection due to its comparative advantages including high mass sensitivity, potential for array configuration, low cost, ease of fabrication as well as wide range of available sensitive material compatibility. However, its application has been limited due to two main disadvantages of the non-uniform mass sensitivity across the electrodes and lower frequency of operation. In this work, in order to overcome these disadvantages, a novel concentric electrode structure combined with the dual inverted mesa structure has been proposed and implemented. It is demonstrated that the developed and optimized concentric electrode has provided a uniform displacement across the QCM's sensing electrode. In addition, the dual inverted mesa design has been implemented in the QCM array in which a high fundamental resonant frequency of 33 MHz has been achieved without interference between the adjacent channels in the sensor array. The interference between the adjacent high frequency QCM channels has been eliminated and therefore, each QCM can function as an individual gas sensor when coated with the designed sensing layers. For 33 MHz, the interference has been eliminated at the optimal center to center between electrode distance (c2c). In the case of 10 MHz array, c2c value of 6 mm is achieved which is lower than the value of c2c achieved on a traditionally un-etched QCM array which was found equal to 6.5 mm. Therefore, the proposed QCM array design is shown to reduce the overall size while enhancing the device sensitivity, uniformity and performance.

Nanoelectromechanical Sensors Based on Suspended 2D Materials.

The unique properties and atomic thickness of two-dimensional (2D) materials enable smaller and better nanoelectromechanical sensors with novel functionalities. During the last decade, many studies have successfully shown the feasibility of using suspended membranes of 2D materials in pressure sensors, microphones, accelerometers, and mass and gas sensors. In this review, we explain the different sensing concepts and give an overview of the relevant material properties, fabrication routes, and device operation principles. Finally, we discuss sensor readout and integration methods and provide comparisons against the state of the art to show both the challenges and promises of 2D material-based nanoelectromechanical sensing.

Anti-Symmetric Mode Vibration of Electrostatically Actuated Clamped-Clamped Microbeams for Mass Sensing.

This paper details study of the anti-symmetric response to the symmetrical electrostatic excitation of a Micro-electro-mechanical-systems (MEMS) resonant mass sensor. Under higher order mode excitation, two nonlinear coupled flexural modes to describe MEMS mass sensors are obtained by using Hamilton’s principle and Galerkin method. Static analysis is introduced to investigate the effect of added mass on the natural frequency of the resonant sensor. Then, the perturbation method is applied to determine the response and stability of the system for small amplitude vibration. Through bifurcation analysis, the physical conditions of the anti-symmetric mode vibration are obtained. The corresponding stability analysis is carried out. Results show that the added mass can change the bifurcation behaviors of the anti-symmetric mode and affect the voltage and frequency of the bifurcation jump point. Typically, we propose a mass parameter identification method based on the dynamic jump motion of the anti-symmetric mode. Numerical studies are introduced to verify the validity of mass detection method. Finally, the influence of physical parameters on the sensitivity of mass sensor is analyzed. It is found that the DC voltage and mass adsorption position are critical to the sensitivity of the sensor. The results of this paper can be potentially useful in nonlinear mass sensors.

An 860 MHz Wireless Surface Acoustic Wave Sensor With a Metal-Organic Framework Sensing Layer for CO2 and CH4

Wireless and passive surface acoustic wave (SAW) devices with nanoporous metal-organic framework (MOF) sensing layers are attractive gas sensors for applications in many fields such as energy industries and air pollution control. Here, we report on enhancing the sensitivity and detection limit of zeolitic imidazolate framework-8 (ZIF-8) MOF-coated SAW reflective delay line mass sensors by increasing the operating frequency for sensitive detection of carbon dioxide (CO2) and methane (CH4) at ambient conditions. In particular, we show at least four times higher sensitivity of an 860 MHz (4-{\mu}m periodicity) SAW reflective delay line coated with a 240 nm thick ZIF-8 compared to the sensitivity of a 430 MHz (8-{\mu}m periodicity) otherwise identical sensor device to the targeted gases. The detection limits of the higher frequency wireless devices for CO2 and CH4 were estimated to be 0.91 vol-% and 7.01 vol-%, respectively. The enhanced sensitivity for higher frequency devices is explained in terms of the frequency dependent acoustic wave energy confinement.

A Design Deviation Decreasing Methodology: Verified With a Piezoelectric Current Sensor

CAD and CAE approach have accelerated sensor design and optimization. But physical sensors tend to be accompanied with multi-physics interaction, making it hard to perform accurate 3D simulation of the sensors. Compared to 3D, 2D simulation’s computing expenses have decreased by 85%, while bringing about a maximum deviation up to 92%. In this paper, a methodology to decrease the deviation while simplifying 3D simulations of cantilever-based sensors into 2D ones are proposed and verified with a piezoelectric current sensor. To make up for the deviation, firstly, comprehensive 2D and 3D simulations are performed within a broad design space. Then, the deviation between 2D and 3D simulation under different design parameters are calculated. Finally, the design parameters and the deviation are used to train a neural network. After training, when new design parameters are input into the network, the corresponding deviation can quickly be predicted and used to revise 2D coarse simulation result. As a result, the deviation between 2D and 3D simulation is below 0.34%, which is a two order of magnitude decreasing compared to the result before being revised. This methodology can not only be used for the design and optimization of piezoelectric current sensor’s, but also can be potentially useful for other cantilever-based sensors, like piezoelectric mass and force sensor.

Fabrication, electrical characterization and sub-ng mass resolution of sub-μm air-gap bulk mode MEMS mass sensors for the detection of airborne particles

In this study, we propose to realize high-performance inertial Micro-Electro-Mechanical Systems (MEMS) mass sensors by the thick oxide as a mask layer fabrication technique. This method enables to reduce the air-gap to sub-μm in capacitively transduced MEMS with optical lithography and has been used to fabricate high aspect ratio sub-μm air-gap bulk mode MEMS mass sensors. MEMS devices have been designed and fabricated with the gap size as small as ~400 nm for ~38 μm thick SOI-based resonators (~95:1). Due to the conical characteristic of the gap, the mean air-gap has also been estimated as ~868 nm with 46 μm depth, which results in ~ 53:1 aspect ratio for the silicon test wafers that have been treated under the same conditions with the SOI-based devices. COMSOL simulation results and fabricated MEMS resonators coherently show that MEMS devices exhibit Lamé mode at 4.099 MHz resonance frequency with the estimated quality factor around 20,000, and extensional mode at 4.467 MHz with the estimated quality factors around 18,000 in the air. The motional resistance has been estimated as small as 27.28 Ω for the Lamé mode operating at 40 V. In this study, two different bulk modes have been considered as sensitive and uniform mass sensors for the detection of airborne particles. Then, minimum mass measurement capability of both modes has been experimentally estimated as 0.51 ng and 0.47 ng for Lamé and extensional modes, respectively. The latter, a proof-of-concept mass measurement has been conducted to deduce the resonance frequency shifts of both modes upon an added mass. This work demonstrates optimization of the thick oxide mask layer fabrication technique and realization of high aspect ratio bulk-mode MEMS mass sensors.

A Microfluidic MEMS-Microbalance Platform With Minimized Acoustic Radiation in Liquid.

In this article, the microfluidic channels that deliver liquid to a microscale thin-film piezoelectric-on-silicon (TPoS) gravimetric resonant sensor are incorporated into the backside of the silicon-on-insulator (SOI) wafer on which the resonator is fabricated. Specifically, a microwell is embedded at the bottom of the disk -shaped TPoS resonator, while a very thin layer of parylene covering the backside of the resonator and the microwell forms an isolation layer between the liquid and the top device-layer features. In this way, the liquid is in contact with the backside of the resonator, while the device-defining trenches and the electrical connections to the resonator stay clear, thus mitigating the acoustic energy loss and undesirable feedthroughs. The impact of the parylene layer thickness on a few symmetric ( S ) and antisymmetric ( A ) Lamb wave modes of the resonator is experimentally studied, and the performance of such modes in the liquid is characterized by filling the microwells through a PDMS-based microfluidic channel. The parylene layer, while marginally affecting the resonator in the air, is found to substantially enhance its performance in the liquid media. Strong resonance peaks with high quality factors ( Q ) are observed for the S modes, among which Q values above 400 are recorded for a specific mode named S (4, 2) (among the highest ever reported). This article can potentially facilitate the realization of highly stable and sensitive resonant mass sensors (i.e., microbalance) for real-time applications. Additionally, the effect of the acoustic energy radiation in the form of evanescent shear and longitudinal waves in liquid on the Q and resonance frequency of the disk resonators is experimentally validated.

Effect of FIB milling on NiTi films and NiTi/Si micro-bridge sensor

Resonance based mass sensors are able to sense tiny fractions of grams based on the resonant frequency shift of a resonator when the resonator is subjected to changes in attached mass or temperature. In our work, NiTi/Si micro-bridge with a design of tunable resonance based sensor was successfully fabricated using Xe+ plasma focused ion beam (FIB). Before fabricating the micro-bridge, an influence of various Xe+ FIB currents on the transformational behavior of NiTi films was tested. In the other part of the present study, the effect of temperature on the vibrating NiTi/Si micro-bridge was examined in a broad range of frequencies. It is suggested that the NiTi film can work as a frequency tuning element in resonance based mass sensors. The shift of the first resonant frequencies of NiTi/Si bilayer micro-bridge with the length, width, thickness and the NiTi/Si thickness ratio being 200 μm, 40 μm, 5.8 μm and 0.29, respectively, is up to 7% with temperature ranging from 25 °C to 100 °C during heating up. The finite element analysis of the micro-bridge is done in order to calibrate the NiTi/Si micro-bridge resonator sensor.

Hybrid Odd Repetitive Controller for Magnetically Suspended Rotor System

Odd-harmonic current induced by mass unbalance and sensor runout in magnetic bearing coil current of magnetically suspended rotor (MSR) system will cause harmonic vibration. In this paper, a hybrid odd repetitive controller (HORC) is proposed to suppress harmonic current in MSR system. On one hand, frequency robustness of the proposed algorithm is better than that of conventional repetitive controller when the fundamental frequency of harmonic current is fluctuant around the nominal value of rotation frequency. On the other hand, the dynamic response is also accelerated. Meanwhile, a stability criterion is presented to prove the stability of MSR system. The proposed algorithm has good potentials for MSR system. Simulation results verify the effectiveness of the proposed method.

Analytical modeling of a magnetically affected cantilever nanoplate-based mass detector

Abstract A new model for a magnetically affected cantilever nanoplate-based mass sensor for detecting attached nanoparticles or long-chain molecule is developed and exact solutions are derived. A novel Hamiltonian-based method incorporating with nonlocal elastic theory is implemented to obtain the analytical solution of the mass sensor. The solutions are verified by comparing with published molecular mechanics and molecular dynamics simulation data and good agreements are recorded. The influences of the foundation modulus, nonlocal parameter, aspect ratio, magnetic field strength and thermal load on the frequency shift are examined. Numerical results show that the performance of the present detector is governed by the design parameters stated above; and applying an in-plane magnetic field is an efficient way to improve the sensitivity of cantilever mass detectors for a specific detector. The meaningful results will directly benefit the predesign and manufacture of such magnetically cantilever nanoplate-based nanosensor.

Self-sensing, tunable monolayer MoS2 nanoelectromechanical resonators

Excellent mechanical properties and the presence of piezoresistivity make single layers of transition metal dichalcogenides (TMDCs) viable candidates for integration in nanoelectromechanical systems (NEMS). We report on the realization of electromechanical resonators based on single-layer MoS2 with both piezoresistive and capacitive transduction schemes. Operating in the ultimate limit of membrane thickness, the resonant frequency of MoS2 resonators is primarily defined by the built-in mechanical tension and is in the very high frequency range. Using electrostatic interaction with a gate electrode, we tune the resonant frequency, allowing for the extraction of resonator parameters such as mass density and built-in strain. Furthermore, we study the origins of nonlinear dynamic response at high driving force. The results shed light on the potential of TMDC-based NEMS for the investigation of nanoscale mechanical effects at the limits of vertical downscaling and applications such as resonators for RF-communications, force and mass sensors.

Suppression of Harmonic Vibration in Magnetically Suspended Centrifugal Compressor Using Zero-Phase Odd-Harmonic Repetitive Controller

Magnetically suspended centrifugal compressor is a better energy-saving choice than ordinary centrifugal compressor in industrial applications. However, harmonic currents, which generate from rotor mass unbalance and sensor runout, cause harmonic vibrations, which deteriorate the stability of the overall system and lead to higher power consumption. The conventional repetitive controller (CRC) has been used to eliminate harmonic vibrations in magnetic bearing systems, but the CRC method has the drawbacks of frequency shift and shallow notch depth that degrade its performance of harmonic currents suppression. In this article, a zero-phase odd repetitive controller (ZORC) is proposed. Compared to the CRC, the ZORC has control action only at odd harmonic frequencies and it has no influence on the closed-loop system at even harmonic frequencies. Besides, the conventional first-order low-pass filter is replaced with the zero-phase low-pass filter and moved outside the internal loop, which dramatically improve its performance of suppressing harmonic currents. The validity and effectiveness of the proposed method are proved both by simulation and experimental results.

Measuring of Cassava Starch Content by Using Strain Gauge

It has been realized an instrument for measuring cassava starch content digitally based on specific gravity method. The instrument is designed using strain gauge, which packing in load cell as a mass sensor, HX711 (Analog to Digital Converter), Arduino Uno as a data processor, LCD, and personal computer. The principles of this instrument are using specific gravity method, which is based on differences of cassava mass in the air and the water. Cassava starch content calculated by Arduino using Sungzikaw equation and displayed in LCD screen. The result showed that the instrument capable measure cassava starch content with the maximum capacity of 2,0 kg and average percentage error of less than 1,5 %.

Modified Repetitive Control for Odd-Harmonic Current Suppression in Magnetically Suspended Rotor Systems

In a magnetically suspended rotor (MSR) system, harmonic current mainly caused by mass imbalance and sensor runout would produce harmonic vibration. Repetitive control (RC) is one remarkable approach for eliminating such harmonics. Conventional RC (CRC) attempts to compensate for all frequency components simultaneously. However, in the practical MSR system, it is usual that the current comprises only odd-harmonic components. This paper investigates a modified odd-harmonic RC (MORC) scheme to respond to this issue. The signal generator of arbitrary-order discrete-time periodic signal is established, by which the general forms of CRC and ORC can be obtained. Besides, it is proved that ORC with halved data memory possesses a faster convergence rate, higher repetitive gain, wider frequency bandwidth at the targeted frequency and greater robustness to frequency fluctuation than CRC. The stability criterion for the MORC-controlled MSR system is proved as well. Simulation and experimental results have highlighted the effectiveness of the proposed approach.

Research and Application of Single Production Data Synchronization Method for Cigarette Maker

Aiming at the shortcomings of sampling in the current cigarette industry product design and development, production process quality control and overall quality evaluation, a method for synchronizing the cigarette unit cigarette data in real time is designed. This method can be used in real time. The data of each cigarette is synchronized in real time based on the time stamp and the cigarette sequence. The results show that the method can cover 100% of the mass sensor data of the current cigarette maker, and the storage speed is exactly the same as the production speed of the cigarette maker, and the storage sequence precision is 100%, and the deviation rate is less than 0.5%.

MEMS Piezoresitive cantilever mass sensor response for detection of volatile organic compounds using Omnicant experimental platform

MEMS piezoresitive cantilever is a system that is utilized to identify VOC molecules like acetone, ethanol, isopropyl and ethyl acetate. These molecules have molecular weights ranging from 46.07gms/mole to 88.1gms/mole. These molecules can be identified due to the deflection changes of the cantilever when the change in the mass occurs due to the deposition of molecules on the cantilever. Thus in this paper the responses from the piezoresistive micro cantilever with different analytes using OMNICANT were obtained.

Study on Unbalanced Magnetic Pulling Analysis and Its Control Method for Primary Helium Circulator of High-Temperature Gas-Cooled Reactor

In addition to providing an extremely clean environment for primary loop of high-temperature gas-cooled reactor (HTR), the primary helium circulator (PHC) using electromagnetic levitation technology also provides an effective means for vibration control. Besides synchronous vibration produced by mass imbalance and sensor runout, double-frequency vibration produced by unbalanced magnetic pull (UMP) is serious in PHC engineering prototype (PHC-EP). In this paper, we firstly analyzed the mechanism of UMP and the multi-frequency vibration characteristics in combination with the PHC-EP. Then we put forward a distributed iterative learning control (ILC) algorithm and a parallel control scheme to suppress the periodic vibrations. Finally, we verified the methods by carrying out experimental researches on the active magnetic bearing (AMB) bench of PHC-EP. The results show that the methods put forward in this paper have significant control effect on the double-frequency vibration generated by UMP of the PHC-EP and provide theoretical and practical references for the PHC safe operation in HTR.

The nonlocal frequency behavior of nanomechanical mass sensors based on the multi-directional vibrations of a buckled nanoribbon

Considering the potential applications of the buckled structures as nanomechanical mass sensors, this paper presents an analytical method to solve the frequency shifts of the first-order transverse and longitudinal vibration modes when a mass attaches on the surface of a buckled nanoribbon based on the nonlocal elastic theory and the Lagrange's motion equation. The first-order transverse and longitudinal vibration modes of the buckled nanoribbon are introduced. A comparison between the analytic solution and the finite element analysis (FEA) is presented. Then, the effects of the compressive strain, the magnitude and location of attached mass, the nonlocal parameter, and attached mass numbers on the frequency shifts are presented. From example calculations, it is seen that the magnitude of attached mass increases the frequency shifts of the first-order modes, except the first-order transverse vibration mode at the location Z1=0. The frequency shifts for the first-order transverse and longitudinal vibration modes are different, and could be used as important principles in mass sensing. What's more, the compressive strain and the nonlocal parameter play significant roles on the sensing process of the buckled nanoribbon. The results could serve as useful references for the fabrications and applications of buckled structures based nanomechanical mass sensors.

A Hadoop Processing Method for Massive Sensor Network Data Based on Internet of Things

Based on the analysis of the architecture of the Internet of Things service platform and the key technologies of cloud computing, a massive sensing information processing scheme based on the Internet of Things service platform is proposed. The scheme first proposes a system architecture model that can satisfy the massive sensor information processing in an open platform environment, and designs multiple functional unit modules of the system. By combining these functional units, service configurability can be realized, facing thousands of services and Tenant. Then, Hadoop open source framework is used to realize the distributed computing of the system, which makes full use of the processing advantages of MapReduce computing model, HBase distributed database and HDFS distributed file system in Hadoop framework, and uses Oracle database as a supplement to realize the system high. Finally, the mass sensor information was deployed and tested. The effectiveness of the Hadoop processing method was verified by analyzing the results of MapReduce parallel computing experiments. The average cache hit rate is 93.1%, which has a high cache hit rate, greatly reduces MySQL database I/O, and improves system performance.

Research and Application of Glycoprotein Sensors Based on Glycosyl Recognition

Abstract Glycoprotein is a binding protein whose structure is mainly determined by the content of sugars and proteins and the peptide bonds to which it binds. There are many kinds of glycoproteins, and they can be classified into lectin, hormone, enzyme and immunoglobulin according to the clinical role in the medical field. Glycoproteins have a variety of biological functions and are of great significance in the medical and biological fields. In order to study the biological information related to glycoproteins, it is necessary to establish a highly sensitive and efficient analytical detection method for glycoproteins. The assay of glycoproteins includes separation and purification method, structural analysis and content determination. The commonly used methods for glycoproteins determination are mass spectrometry (MS), chromatography-mass spectrometry, surface excimer resonance, and enzyme-linked immunosorbent assay (ELISA), etc. In recent years, in the detection of glycoproteins, the research and application of sensors have gradually increased. This paper briefly summarized the analysis methods of glycoproteins and reviewed the research and application of glycoprotein biosensors based on glycosyl recognition. The glycoprotein biosensors including electrochemical sensors, optical sensors and mass sensors were introduced in detail. The future development direction of glycoprotein sensors was also prospected.