Mode-Dependent Selective Detection of Humidity and Helium Using Electromagnetically Actuated Clamped Guided MEMS Resonators

2021 ◽  
Author(s):  
Usman Yaqoob ◽  
Nizar Jaber ◽  
Nouha Alcheikh ◽  
Mohammad I. Younis
Keyword(s):  
Thermal Conductivity ◽  
Mass Motion ◽  
Flexural Mode ◽  
Mems Resonator ◽  
Mems Resonators ◽  
Out Of Plane ◽  
A New Technique ◽  
Flexural Beam ◽  
Detection Mechanisms ◽  
Electromagnetically Actuated

Abstract In this work, we demonstrate a selective gas sensor based on monitoring two different detection mechanisms; absorption and thermal conductivity. To illustrate the concept, we utilize a resonator composed of a clamped-guided arch beam connected to flexural beams and a T-shaped moveable mass. The resonator has two distinct out-of-plane modes in which the mass motion dominates the first mode while the motion of the flexural beam dominates the second mode. A highly disperse graphene oxide (GO) solution is prepared and drop-casted over the moveable mass structure using the inkjet printer for humidity sensing. On the other hand, the He is detected using the hot flexural beams. The results show no significant effect of humidity on the flexural mode (FM) nor for He on the mass mode (MM). This indicates a new technique for selectivity and identification. The device shows good sensitivity (50.1% to 50% RH @ MM and 39.2% to 50% He @ FM: (Vac = 1.5V)), linearity, and repeatability with excellent selectivity. It is demonstrated that the FM has great potential for detecting and categorizing different gases according to their thermal conductivity. The demonstrated multimode MEMS resonator can be a promising approach for the development of smart, highly selective, and sensitive gas/chemical sensors.

Design of a MEMS Resonant Wind Sensor on Airplane Wing

2013 ◽  
Vol 562-565 ◽  
pp. 436-440
Author(s):  
Chao Wei Si ◽  
Guo Wei Han ◽  
Jin Ning ◽  
Wei Wei Zhong ◽  
Fu Hua Yang
Keyword(s):  
High Vacuum ◽  
Pressure Change ◽  
Wind Pressure ◽  
Damping Factor ◽  
Deep Reactive Ion Etching ◽  
Mems Resonator ◽  
Mems Resonators ◽  
Element Simulation ◽  
Airplane Wing ◽  
Soi Substrates

A new kind of wind sensor made up of MEMS resonators is designed in the paper capable of sensing the lift, the resistance and the turbulence of airplane wings by mounting on the surface. The designed wind sensor is made up of four MEMS wind pressure gauges fixed around a square wind resistance block which used to block the wind to change the wind pressure on the surface, and the change of wind pressure is detected by MEMS wind pressure gauges to reveal the air condition on the surface of the airplane wings. As known, a MEMS resonator is a second-order resonant system whose damping factor is mainly dependent on the air pressure, and the characteristic is often used to detecting the airtightness of a sealed chamber for the damping factor is sensitive under high vacuum, while a MEMS resonator with the damping factor sensitive at atmospheric pressure is designed in this paper for sensing wind pressure change, and the MEMS resonator is manufactured on SOI substrates with deep reactive ion etching technology. Also relations between the wind pressure change and the wind speed around a block at atmosphere is revealed by finite element simulation. Compared to traditional wind sensors such as anemometers and Venturi tubes, the designed MEMS wind sensor with a very small size is suitable to mount on different zones of a wing with a large amount to monitor the air condition and have less influence on air flow.

Thermal Conductivity Reduction in Few-Layer Graphene

2011 ◽  
Author(s):  
Dhruv Singh ◽  
Jayathi Y. Murthy ◽  
Timothy S. Fisher
Keyword(s):  
Thermal Conductivity ◽  
Weak Coupling ◽  
Phonon Scattering ◽  
Single Layer ◽  
Acoustic Mode ◽  
Single Layer Graphene ◽  
Boltzmann Transport ◽  
Layer Graphene ◽  
Out Of Plane ◽  
Few Layer Graphene

Using the linearized Boltzmann transport equation and perturbation theory, we analyze the reduction in the intrinsic thermal conductivity of few-layer graphene sheets accounting for all possible three-phonon scattering events. Even with weak coupling between layers, a significant reduction in the thermal conductivity of the out-of-plane acoustic modes is apparent. The main effect of this weak coupling is to open many new three-phonon scattering channels that are otherwise absent in graphene. The highly restrictive selection rule that leads to a high thermal conductivity of ZA phonons in single-layer graphene is only weakly broken with the addition of multiple layers, and ZA phonons still dominate thermal conductivity. We also find that the decrease in thermal conductivity is mainly caused by decreased contributions of the higher-order overtones of the fundamental out-of-plane acoustic mode. Moreover, the extent of reduction is largest when going from single to bilayer graphene and saturates for four layers. The results compare remarkably well over the entire temperature range with measurements of of graphene and graphite.

ROM of Superharmonic Resonance of Second Order of Electrostatically Actuated MEMS Resonators

2015 ◽  
Author(s):  
Dumitru I. Caruntu ◽  
Christian Reyes
Keyword(s):  
Second Order ◽  
Voltage Response ◽  
Order Model ◽  
Reduced Order ◽  
Superharmonic Resonance ◽  
Electrostatically Actuated ◽  
Mems Resonator ◽  
Mems Resonators ◽  
Method Effects ◽  
Ground Plate

This paper deals with the voltage-amplitude response (or voltage response) of superharmonic resonance of second order of MEMS resonator sensors under electrostatic actuation. The system consists of a MEMS flexible cantilever above a parallel ground plate. The AC frequency of actuation is near one fourth the natural frequency. The voltage response of the superharmonic resonance of second order of the structure is investigated using the Reduced Order Model (ROM) method. Effects of voltage and damping voltage response are reported.

scholarly journals Thermal transport properties of decagonal quasicrystals and their approximants

2013 ◽  
Vol 1517 ◽  
Author(s):  
Petar Popčević ◽  
Ante Bilušić ◽  
Kristijan Velebit ◽  
Ana Smontara
Keyword(s):  
Thermal Conductivity ◽  
Electrical Resistivity ◽  
Transport Properties ◽  
Heat Transport ◽  
Thermal Transport ◽  
Strong Relationship ◽  
Decagonal Quasicrystal ◽  
Decagonal Quasicrystals ◽  
Plane Anisotropy ◽  
Out Of Plane

ABSTRACTTransport properties (thermal conductivity, electrical resistivity and thermopower) of decagonal quasicrystal d-AlCoNi, and approximant phases Y-AlCoNi, o-Al13Co4, m-Al13Fe4, m-Al13(Fe,Ni)4 and T-AlMnFe have been reviewed. Among all presented alloys the stacking direction (periodic for decagonal quasicrystals) is the most conductive one for the charge and heat transport, and the in/out-of-plane anisotropy is much larger than the in-plane anisotropy. There is a strong relationship between periodicity length along stacking direction and anisotropy of transport properties in both quasicrystals and their approximants suggesting a decrease of the anisotropy with increasing number of stacking layers.

Dynamic behaviours of the Double-end tuning fork based comb-driven microelectromechanical resonators for modulating the magnetic flux synchronously

2021 ◽  
Author(s):  
Zhenxi Liu ◽  
Jiamin Chen ◽  
Wuhao Yang ◽  
Tianyi Zheng ◽  
Qifeng Jiao ◽  
...  
Keyword(s):  
Detection Limit ◽  
Magnetic Flux ◽  
Resonance Frequency ◽  
Tuning Fork ◽  
Paper Making ◽  
Initial Space ◽  
Mems Resonator ◽  
Mems Resonators ◽  
Mems Fabrication ◽  
First Time

Abstract MEMS resonators have been widely used in the magneto-resistive (MR) sensor for modulating the magnetic flux to enhance the detection limit. However, the manufacturing tolerances in MEMS fabrication processes make it challenging to fabricate the identical resonators with the same vibration frequency, which greatly decreases the detection limit of the MR sensor. To synchronize the MEMS resonators and improve the performance of the MR sensor, the double end tuning fork (DETF) based comb-driven MEMS resonators is proposed in this paper, making the system operate at the out-of-phase mode to complete the synchronization. The dynamic behaviour of the resonators is investigated through theoretical analysis, numerical solution based on MATLAB code and Simulink, and experimental verification. The results show that the transverse capacitances in the comb will significantly affect the resonance frequency due to the second-order electrostatic spring constant. It is the first time to observe the phenomenon that the resonant frequency increases with the increase of the bias, and it can also decrease with increasing the bias through adjusting the initial space between the fixed finger and the moving mass, they are different from the model about spring softening and spring hardening. Besides, the proposed DETF-based comb-driven resonators can suppress the in-phase and out-of-phase mode through adjusting the driving and sensing ports, and sensing method, meanwhile make the magnetic flux modulation fully synchronized, and maximize the modulation efficiency, and minimize the detection limit. These characteristics are appropriate for the MR sensor, even other devices that need to adjust the resonance frequency and vibration amplitude. Furthermore, the model and the design can also be extended to characteristic the single end tuning fork (SETF) based MEMS resonator and other MEMS-based MR sensors.

scholarly journals Phonon hydrodynamics and ultrahigh–room-temperature thermal conductivity in thin graphite

Science ◽  
2020 ◽  
Vol 367 (6475) ◽  
pp. 309-312 ◽  
Author(s):  
Yo Machida ◽  
Nayuta Matsumoto ◽  
Takayuki Isono ◽  
Kamran Behnia
Keyword(s):  
Thermal Conductivity ◽  
Thermal Diffusivity ◽  
Wide Temperature Range ◽  
Room Temperature ◽  
Phonon Dispersion ◽  
High Conductivity ◽  
Temperature Range ◽  
A Value ◽  
Out Of Plane ◽  
Intimate Link

Allotropes of carbon, such as diamond and graphene, are among the best conductors of heat. We monitored the evolution of thermal conductivity in thin graphite as a function of temperature and thickness and found an intimate link between high conductivity, thickness, and phonon hydrodynamics. The room-temperature in-plane thermal conductivity of 8.5-micrometer-thick graphite was 4300 watts per meter-kelvin—a value well above that for diamond and slightly larger than in isotopically purified graphene. Warming enhances thermal diffusivity across a wide temperature range, supporting partially hydrodynamic phonon flow. The enhancement of thermal conductivity that we observed with decreasing thickness points to a correlation between the out-of-plane momentum of phonons and the fraction of momentum-relaxing collisions. We argue that this is due to the extreme phonon dispersion anisotropy in graphite.

Investigation of the thermal conductivity of the pentatellurides (Hf1-XZrXTe5) using the parallel thermal conductance technique.

2000 ◽  
Vol 626 ◽  
Author(s):  
B. M. Zawilski ◽  
R. T. Littleton ◽  
Terry M. Tritt ◽  
D. R. Ketchum ◽  
J. W. Kolis
Keyword(s):  
Thermal Conductivity ◽  
Low Temperature ◽  
Radiation Effects ◽  
Thermal Conductance ◽  
Small Samples ◽  
Formidable Challenge ◽  
Conductance Technique ◽  
Small Needle ◽  
A New Technique ◽  
Future Work

ABSTRACTThe pentatelluride materials (Hf1-XZrXTe5) have recently garnered much interest as a potential low temperature thermoelectric material. Their power factor exceeds that of the current Bi2Te3 materials over the temperature range 150 K < T < 350 K. A formidable challenge has been the capability of measuring the thermal conductivity of small needle-like samples (2.0 × 0.05 × 0.1 mm3) such as pentatellurides (HfXZr1-XTe5) due to heat loss and radiation effects. However in order to fully evaluate any material for potential thermoelectric use, the determination of the thermal conductivity of the material is necessary. We have recently developed a new technique called the parallel thermal conductance (PTC) technique to measure the thermal conductivity of such small samples. In this paper we describe the PTC method and measurements of the thermal conductivity of the pentatelluride materials will be presented for the first time. The potential of these materials for low temperature thermoelectric applications will be further evaluated given these results as well as future work and directions will be discussed.

Increasing Efficiencies of Thermoelectric Devices Through Angular Interface Geometries

2009 ◽  
Author(s):  
D. P. Sellan ◽  
C. H. Amon
Keyword(s):  
Thermal Conductivity ◽  
Figure Of Merit ◽  
Equation Model ◽  
Boltzmann Transport ◽  
Thermoelectric Efficiency ◽  
Thermoelectric Figure ◽  
Subsequent Increase ◽  
Acoustic Mismatch ◽  
Out Of Plane ◽  
Plane Direction

The phonon Boltzmann transport equation model is used to evaluate the reduction of out-of-plane thermal conductivity and subsequent increase in thermoelectric figure of merit when an angular interface is patterned between a germanium thin-film and silicon substrate. According to the acoustic mismatch model, the angular structure reduces the out-of-plane thermal conductivity by spatially redistributing phonons traveling in the out-of-plane direction. Simulation results demonstrate a 43% reduction in out-of-plane thermal conductivity when operating in the fully ballistic regime. This decrease in phononic thermal conductivity would result in an increase of intrinsic thermoelectric efficiency by a factor of 1.75.

A Tiny Detector Made of a Self-Heated Thermistor for Determining Thermal Conductivity of Biomaterials in Temperature Range 233~313K

2002 ◽  
Author(s):  
H. F. Zhang ◽  
S. X. Cheng ◽  
L. Q. He ◽  
A. L. Zhang ◽  
Y. Zheng ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Carotid Artery ◽  
Temperature Rise ◽  
Measurement Errors ◽  
Homogeneous Medium ◽  
Standard Samples ◽  
Temperature Range ◽  
A New Technique ◽  
Maximum Measurement

In this paper, a new technique, using a tiny thermistor with 0.3~0.5mm in diameter to determine thermal conductivity of biomaterials in wide temperature range, has been developed. Based on steady spherical heat transfer in an infinite homogeneous medium, thermal conductivity of the measured medium can be determined by power applied and temperature rise of the thermistor. Compared with recommended values, maximum measurement errors of standard samples, aqueous glycol and CaCl2 solutions, water and ice, are 5.1% in temperature range 233~313K. The thermal conductivities of rabbit’s liver, kidney, heart and carotid artery in temperature range 233~293K are determined. Error caused by measurement parameters, effects of the finite scale of the measured medium and the decoupler between the thermistor and the medium are analyzed.

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