Heat Transfer From Freely Suspended Bimaterial Microcantilevers

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Arvind Narayanaswamy ◽  
Ning Gu
Keyword(s):  
Heat Transfer ◽  
Atmospheric Pressure ◽  
Coefficient Of Thermal Expansion ◽  
Thermal Conductance ◽  
Temperature Changes ◽  
Atomic Force ◽  
Physical Chemical ◽  
Freely Suspended ◽  
Effective Heat Transfer Coefficient

Bimaterial atomic force microscope cantilevers have been used extensively over the last 15 years as physical, chemical, and biological sensors. As a thermal sensor, the static deflection of bimaterial cantilevers, due to the mismatch of the coefficient of thermal expansion between the two materials, has been used to measure temperature changes as small as 10−6 K, heat transfer rate as small as 40 pW, and energy changes as small as 10 fJ. Bimaterial cantilevers have also been used to measure “heat transfer-distance” curves—a heat transfer analogy of the force-distance curves obtained using atomic force microscopes. In this work, we concentrate on the characterization of heat transfer from the microcantilever. The thermomechanical response of a bimaterial cantilever is used to determine the (1) thermal conductance of a bimaterial cantilever, and (2) overall thermal conductance from the cantilever to the ambient. The thermal conductance of a rectangular gold coated silicon nitride cantilever is Gc=4.09±0.04 μW K−1. The overall thermal conductance from the cantilever to the ambient (at atmospheric pressure) is Ga=55.05±0.69 μW K−1. The effective heat transfer coefficient from the cantilever to the ambient (at atmospheric pressure) is determined to be ≈3400 W m−2 K−1.

Thermal Characterization of Bi-Material Microcantilevers: Thermal Conductance and Microscale Convection

2009 ◽  
Author(s):  
Arvind Narayanaswamy ◽  
Ning Gu
Keyword(s):  
Heat Transfer ◽  
Thermal Environment ◽  
Coefficient Of Thermal Expansion ◽  
Ambient Pressure ◽  
Thermal Conductance ◽  
Thermal Characterization ◽  
Temperature Changes ◽  
Atomic Force ◽  
The Heat Transfer Coefficient

Bi–material atomic force microscope cantilevers have been used extensively over the last 15 years as physical, chemical, and biological sensors. As a thermal sensor, the static deflection of bi–material cantilevers due to the mismatch of the coefficient of thermal expansion between the two materials has been used to measure temperature changes as small as 10−5 K, heat transfer rate as small as 40 pW, and energy changes as small as 10 fJ. Bi–material cantilevers have also been use to measure “heat transfer - distance” curves a heat transfer analogy of the force–distance curves obtained using atomic force microscopes. In this work, we concentrate on characterization of heat transfer from the microcantilever. The two quantities that we focus on are the thermal conductance of the cantilever, Gcant (units WK−1), and the thermal conductance due to microscale convection from the cantilever to the ambient fluid, Gconv (units WK−1). The deflection of the cantilever to changes in its thermal environment is measured using the shift in position, on a position sensitive detector, of a laser beam focused at the tip of the cantilever. By determining the response of the microcantilever to (1) uniform temperature rise of the ambient, and (2) change in power absorbed at the tip, the thermal conductance of heat transfer from the cantilever can be determined. When the experiment is performed at low enough ambient pressure so that convection is unimportant (¡ 0.1 Pa), Gcant can be measured. When the experiment is performed at atmospheric pressure the heat transfer coefficient due to convection from the cantilever can be determined.

Measurement of Heat Flux From Fires

Volume 4 ◽  
2004 ◽  
Author(s):  
Cecilia S. Lam ◽  
Alexander L. Brown ◽  
Elizabeth J. Weckman ◽  
Walter Gill
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Unit Area ◽  
Inverse Heat Conduction ◽  
Thermal Impact ◽  
Temperature Changes ◽  
One Dimensional ◽  
Conduction Heat Transfer ◽  
Flux Measurements

Heat flux is an important parameter for characterization of the thermal impact of a fire on its surroundings. However, heat flux cannot be measured directly because it represents the rate of heat transfer to a unit area of surface. Therefore, most heat flux measurements are based on the measurement of temperature changes at or near the surface of interest [1,2]. Some instruments, such as the Gardon gauge [3] and the thermopile [2], measure the temperature difference between a surface and a heat sink. In radiation-dominated environments, this difference in temperature is often assumed to be linearly related to the incident heat flux. Other sensors measure a surface and/or interior temperature and inverse heat conduction methods frequently must be employed to calculate the corresponding heat flux [1,4]. Typical assumptions include one-dimensional conduction heat transfer and negligible heat loss from the surface. The thermal properties of the gauge materials must be known and, since these properties are functions of temperature, the problem often becomes non-linear.

Characterization of Heat Propagation along Single Tin Dioxide Nanobelt Using the Thermoreflectance Method

2007 ◽  
Vol 1022 ◽  
Author(s):  
Xi Wang ◽  
Younes Ezzahri ◽  
James Christofferson ◽  
Yi Zhang ◽  
Ali Shakouri ◽  
...  
Keyword(s):  
Thin Film ◽  
Heat Transfer ◽  
High Resolution ◽  
Tin Dioxide ◽  
Imaging Technique ◽  
Thermal Conductance ◽  
Heat Propagation ◽  
Transfer Properties ◽  
Thin Film Devices

AbstractIn this paper, we studied heat transfer properties of a 230nm wide，450nm thick and 5.4 m long single tin dioxide nanobelt using non-contacted high resolution thermoreflectance imaging technique. Temperature difference across the nanobelt was created by attaching its both ends to a microfabricated thin film heater and sensor pair. High resolution thermal images of the nanobelt and thin film devices were obtained at variant pulsing current amplitudes and frequencies, which allowed us to study the inherent thermal conductance of the nanobelt. Thermal expansion induced thermoreflectance coefficient change is also discussed in this paper.

scholarly journals Experiments on Temperature Changes of Microbolometer under Blackbody Radiation and Predictions Using Thermal Modeling by COMSOL Multiphysics Simulator

Sensors ◽  
2018 ◽  
Vol 18 (8) ◽  
pp. 2593 ◽  
Author(s):  
Yu-Zhen Deng ◽  
Shiang-Feng Tang ◽  
Hong-Yuan Zeng ◽  
Zheng-Yuan Wu ◽  
Der-Kuo Tung
Keyword(s):  
Heat Transfer ◽  
Thermal Conductance ◽  
Blackbody Radiation ◽  
Heat Transfer Model ◽  
Comsol Multiphysics ◽  
Transfer Model ◽  
Temperature Dependent ◽  
Temperature Changes ◽  
Radiated Energy

In this study, we study a heat transfer model, with the surface of the microbolometer device receiving radiation from blackbody constructed using a COMSOL Multiphysics simulator. We have proposed three kinds of L-type 2-leg and 4-leg with the pixel pitch of 35 μm based on vanadium oxide absorbent membrane sandwiched with top passivated and bottom Si3N4 supporting films, respectively. Under the blackbody radiation, the surface temperature changes and distributions of these samples are simulated and analyzed in detail. The trend of change of the temperature dependent resistance of the four kinds of bolometer devices using the proposed heat transfer model is consistent with the actual results of the change of resistance of 4 samples irradiated with 325 K blackbody located in the front distance of 5 cm. In this paper, ΔT indicates the averaged differences of the top temperature on the suspended membrane and the lowest temperature on the post of legs of the microbolometers. It is shown that ΔT ≈ 17 mK is larger in nominal 2-leg microbolometer device than that of 4-leg one and of 2-leg with 2 μm × 2 μm central square hole and two 7.5 μm × 2 μm slits in suspended films. Additionally, only ΔT ≈ 5 mK with 4-leg microbolometer device under the same radiated energy of 325 K blackbody results from the larger total thermal conductance.

Electron microscope characterization of MOCVD-grown gap layers on Si

1986 ◽  
Vol 44 ◽  
pp. 724-725
Author(s):  
K.M. Jones ◽  
M.M. Al-Jassim ◽  
J.M. Olson
Keyword(s):  
Atmospheric Pressure ◽  
Vapour Deposition ◽  
Chemical Vapour ◽  
Organic Chemical ◽  
Lattice Match ◽  
Si Substrates ◽  
Metal Organic ◽  
Good Lattice ◽  
Antiphase Domains

The epitaxial growth of III-V semiconductors on Si for integrated optoelectronic applications is currently of great interest. GaP, with a lattice constant close to that of Si, is an attractive buffer between Si and, for example, GaAsP. In spite of the good lattice match, the growth of device quality GaP on Si is not without difficulty. The formation of antiphase domains, the difficulty in cleaning the Si substrates prior to growth, and the poor layer morphology are some of the problems encountered. In this work, the structural perfection of GaP layers was investigated as a function of several process variables including growth rate and temperature, and Si substrate orientation. The GaP layers were grown in an atmospheric pressure metal organic chemical vapour deposition (MOCVD) system using trimethylgallium and phosphine in H2. The Si substrates orientations used were (100), 2° off (100) towards (110), (111) and (211).

Characterization of photosystem II with the atomic-force microscope

1992 ◽  
Vol 50 (2) ◽  
pp. 1146-1147
Author(s):  
Kathleen M. Marr ◽  
Mary K. Lyon
Keyword(s):  
Photosystem Ii ◽  
Atomic Force Microscope ◽  
Three Dimensional ◽  
Biologically Active ◽  
Atomic Force ◽  
Freeze Etching ◽  
Image Averaging ◽  
Oxygen Evolving ◽  
Averaging Techniques

Photosystem II (PSII) is different from all other reaction centers in that it splits water to evolve oxygen and hydrogen ions. This unique ability to evolve oxygen is partly due to three oxygen evolving polypeptides (OEPs) associated with the PSII complex. Freeze etching on grana derived insideout membranes revealed that the OEPs contribute to the observed tetrameric nature of the PSIl particle; when the OEPs are removed, a distinct dimer emerges. Thus, the surface of the PSII complex changes dramatically upon removal of these polypeptides. The atomic force microscope (AFM) is ideal for examining surface topography. The instrument provides a topographical view of individual PSII complexes, giving relatively high resolution three-dimensional information without image averaging techniques. In addition, the use of a fluid cell allows a biologically active sample to be maintained under fully hydrated and physiologically buffered conditions. The OEPs associated with PSII may be sequentially removed, thereby changing the surface of the complex by one polypeptide at a time.

Rapid, Refined, and Robust Method for Expression, Purification, and Characterization of Recombinant Human Amyloid-beta M1-42

2019 ◽  
Author(s):  
Priya Prakash ◽  
Travis Lantz ◽  
Krupal P. Jethava ◽  
Gaurav Chopra
Keyword(s):  
Amyloid Beta ◽  
Western Blots ◽  
Force Microscopy ◽  
E Coli ◽  
Atomic Force ◽  
Set Up ◽  
Short Time

Amyloid plaques found in the brains of Alzheimer’s disease (AD) patients primarily consists of amyloid beta 1-42 (Ab42). Commercially, Ab42 is synthetized using peptide synthesizers. We describe a robust methodology for expression of recombinant human Ab(M1-42) in Rosetta(DE3)pLysS and BL21(DE3)pLysS competent E. coli with refined and rapid analytical purification techniques. The peptide is isolated and purified from the transformed cells using an optimized set-up for reverse-phase HPLC protocol, using commonly available C18 columns, yielding high amounts of peptide (~15-20 mg per 1 L culture) in a short time. The recombinant Ab(M1-42) forms characteristic aggregates similar to synthetic Ab42 aggregates as verified by western blots and atomic force microscopy to warrant future biological use. Our rapid, refined, and robust technique to purify human Ab(M1-42) can be used to synthesize chemical probes for several downstream in vitro and in vivo assays to facilitate AD research.

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