Local Microflow Control Using Photothermal Viscosity Distribution

A novel method of microflow control by locally heated liquid using an optical technique is described in this paper. Microflow control in the present study utilizes temperature dependence of the fluid property which becomes dominant in microscale. Since it is known that viscosity has strong temperature dependence, a local viscosity distribution has a potential to change microflow behavior. The purpose of the present study is to validate this concept of microflow control by using the local distribution of viscosity. In order to induce the temperature variation, photothermal effect is utilized. Absorption of a laser beam causes the local heating spot. This method has attractive features such as non-intrusive and high time- and spatial- resolution, and also has a possibility for a flexible flow control. We have developed an experimental system to irradiate focused laser beam on a flow in a microfluidic device and to measure velocity and temperature field of the microflow. The local temperature rise in microchannel flow is generated by a focused laser spot. During the laser irradiation, the velocity profile of the liquid flow in microchannel with 500 μm in width and 50 μm in height was measured by micro-PIV (Particle Image Velocimetry). The temperature measurement of the flow field was performed by micro-LIF (Laser-Induced Fluorescence). Around the heated area, the local increase of the flow velocity can be observed. It is found that the effect depends on the laser intensity and is independent of the bulk velocity. In addition, numerical simulation was conducted to identify the dominant factor causing the velocity change. As a simulation result, the cause of the velocity variation is the viscosity decrease corresponding to the temperature rise in fluid. Possibility of microflow control using the photothermal viscosity distribution is confirmed.

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Microflow Behavior of Liquid in the Presence of Laser-Induced Temperature Gradient

ASME 5th International Conference on Nanochannels, Microchannels, and Minichannels ◽

10.1115/icnmm2007-30132 ◽

2007 ◽

Author(s):

Masahiro Motosuke ◽

Jun Shimakawa ◽

Shinji Honami

Keyword(s):

Temperature Gradient ◽

Laser Beam ◽

Flow Behavior ◽

Local Temperature ◽

Photothermal Effect ◽

Strong Temperature Dependence ◽

Rectangular Microchannel ◽

Micro Particle Image Velocimetry ◽

Micro Piv ◽

Piv Measurement

A novel technique is presented for non-intrusive microflow control with laser-induced local temperature gradient. In microscale, fluid behavior is quite different from that in macroscale, especially an effect of fluid or interfacial properties on microflow becomes significant. The technique described in this paper utilizes the property change of fluids caused by a light-induced temperature change, i.e., photothermal effect. Absorption of a focused laser beam causes the local spot in temperature. Since the viscosity of general fluids has strong temperature dependence, a generation of local temperature gradient in microfluids results in the corresponding viscosity distribution, which is directly related to the flow behavior in microflow. In order to demonstrate the validity of this concept, we have developed an experimental system to irradiate focused laser beam on a flow in a microfluidic device and to measure velocity profile of the microflow simultaneously. As a heating source, a compact laser diode (LD) with the visible wavelength of 635nm is employed. Velocity measurement is performed by a micro particle image velocimetry (micro-PIV) technique. Optical separation between LD absorption and excitation/emission of fluorescent particle for micro-PIV measurement is confirmed. Change in the microflow behavior in a rectangular microchannel (500 μm × 50 μm) during the LD irradiation due to the photothermal effect is observed.

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Temperature Dependence of the Critical Electron Dose for Fatty Acid Monolayers

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100053188 ◽

1982 ◽

Vol 40 ◽

pp. 78-79

Author(s):

Kenneth H. Downing ◽

Robert M. Glaeser

Keyword(s):

Electron Beam ◽

Fatty Acid ◽

Inelastic Scattering ◽

Temperature Dependence ◽

Structural Damage ◽

Direct Result ◽

Second Step ◽

Strong Temperature Dependence ◽

Electron Dose ◽

Covalent Bonds

The structural damage of molecules irradiated by electrons is generally considered to occur in two steps. The direct result of inelastic scattering events is the disruption of covalent bonds. Following changes in bond structure, movement of the constituent atoms produces permanent distortions of the molecules. Since at least the second step should show a strong temperature dependence, it was to be expected that cooling a specimen should extend its lifetime in the electron beam. This result has been found in a large number of experiments, but the degree to which cooling the specimen enhances its resistance to radiation damage has been found to vary widely with specimen types.

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Temperature-Driven Spin Reorientation Transition in CoPt/AlN Multilayer Films

Journal of Nanomaterials ◽

10.1155/2012/814162 ◽

2012 ◽

Vol 2012 ◽

pp. 1-7

Author(s):

Wupeng Cai ◽

Shinji Muraishi ◽

Ji Shi ◽

Yoshio Nakamura ◽

Wei Liu ◽

...

Keyword(s):

Temperature Dependence ◽

Mean Field ◽

Multilayer Films ◽

Spin Reorientation ◽

Strong Temperature Dependence ◽

Mean Field Model ◽

Spin Reorientation Transition ◽

Magnetoelastic Effect ◽

Out Of Plane ◽

Interface Anisotropy

Spin reorientation transition phenomena from out-of-plane to in-plane direction with increasing temperature are observed for the 500°C annealed CoPt/AlN multilayer films with different CoPt layer thicknesses. CoPt-AlN interface and volume anisotropy contributions, favoring out-of-plane and in-plane magnetization, respectively, are separately determined at various temperatures. Interface anisotropy exhibits much stronger temperature dependence than volume contribution, hence the temperature-driven spin reorientation transition occurs. Interface anisotropy in this work consists of Néel interface anisotropy and magnetoelastic effect. Magnetoelastic effect degrades rapidly and changes its sign from positive to negative above 200°C, because of the involvement of stress state in CoPt films with temperature. By contrast, Néel interface anisotropy decays slowly, estimated from a Néel mean field model. Thus, the strong temperature dependence of CoPt-AlN interface anisotropy is dominated by the change of magnetoelastic effect.

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Thermochromism of Highly Luminescent Photopolymer Flexible Films Based On Eu (III) Salts Confined in Polysulfone

Materials ◽

10.3390/ma13235394 ◽

2020 ◽

Vol 13 (23) ◽

pp. 5394

Author(s):

Mani Outis ◽

João Paulo Leal ◽

Maria Helena Casimiro ◽

Bernardo Monteiro ◽

Cláudia Cristina Lage Pereira

Keyword(s):

Thermal Stability ◽

Ionic Liquid ◽

Melting Point ◽

Quantum Yield ◽

Thermal Behavior ◽

Temperature Dependence ◽

Strong Temperature Dependence ◽

Host Matrix ◽

Flexible Films ◽

First Time

Here we discuss the influence of two different cations on the emissive properties of the highly emissive [Eu(fod)4]− anion. The studied Eu(III) salts were [C16Pyr][Eu(fod)4] (1), and the previously reported [Chol][Eu(fod)4]. C16Pyr stands for N-cetylpyridinium, Chol for cholinium and fod for 1,1,1,2,2,3,3-heptafluoro-7,7-dimethyloctane-4,6-dionate. 1 is classified as ionic liquid, with melting point close to 60 °C, and presented a luminescence quantum yield of (ϕ) 100%. Ultrabright emissive photopolymers were obtained for the first time using polysulfone as the host matrix. The films were prepared with incorporation of 10% (w/w) of 1 and [Chol][Eu(fod)4] in the polymeric matrix, which improved its thermal stability. Additionally, the luminescence of CholEu(fod)4/PSU presented a strong temperature dependence with a ratiometric thermal behavior.

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Effects of Local Heating and Premelting in the Terminal Part of the e+ Track

Materials Science Forum ◽

10.4028/www.scientific.net/msf.733.15 ◽

2012 ◽

Vol 733 ◽

pp. 15-18 ◽

Cited By ~ 5

Author(s):

Dmitry Zvezhinskiy ◽

Sergey V. Stepanov ◽

Vsevolod Byakov ◽

Bożena Zgardzińska

Keyword(s):

Melting Point ◽

Temperature Dependence ◽

Local Heating ◽

Bulk Temperature ◽

Melting Points ◽

Terminal Part ◽

Slowing Down ◽

Positronium Lifetime ◽

Molten Region

The terminal part of the e+ track (the positron blob) is formed during ionization slowing down and subsequent ion-electron recombinations produced by a positron. It releases up to 1 keV of energy, which is converted into heat within few picoseconds. If a bulk temperature of a medium is below, but close enough to its melting point, some region of a substance may melt, yielding a peculiar temperature dependence of the lifetime (LT) spectra. We have estimated properties of the molten region with a help of macroscopic heat con- duction equation and suggested a model describing temperature dependence of the ortho- positronium lifetime in frozen methanol, ethanol, butanol and water close to their melting points.

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Mechanics of the influx phase in the jet regurgitant mode of a powered resonance tube

International Journal of Aeroacoustics ◽

10.1177/1475472x19840001 ◽

2019 ◽

Vol 18 (2-3) ◽

pp. 279-298 ◽

Cited By ~ 1

Author(s):

Bhavraj Thethy ◽

David Tairych ◽

Daniel Edgington-Mitchell

Keyword(s):

Shock Wave ◽

High Speed ◽

Fluid Velocity ◽

Velocity Variation ◽

Shock Strength ◽

Velocity Change ◽

Resonator Length ◽

Time Resolved ◽

Reflected Waves ◽

Shock Position

Time-resolved visualisation of shock wave motion within a powered resonant tube (PRT) is presented for the regurgitant mode of operation. Shock position and velocity are measured as functions of both time and space from ultra-high-speed schlieren visualisations. The shock wave velocity is seen to vary across the resonator length for both the incident and reflected waves. Three mechanisms are explored as explanations for the variation in velocity: change in local fluid velocity, variation in shock strength and variations in local temperature. For the incident wave, local fluid velocity and shock strength are extracted from the data and both are demonstrated to contribute to the observed variation, with a non-trivial remainder likely explained by variation in temperature.

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The Temperature-Dependence of the Saturation Voltage for Molecular Assembly System with the Effect of the Intermolecular Spacing

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.774-776.593 ◽

2013 ◽

Vol 774-776 ◽

pp. 593-598

Author(s):

Aissa Boudjella

Keyword(s):

Numerical Simulations ◽

Temperature Dependence ◽

Small Group ◽

Electronic Transport ◽

Temperature Rise ◽

Current Flow ◽

Molecular Assembly ◽

One Dimension ◽

Assembly System ◽

Saturation Region

Numerical simulations have been performed to investigate the effect of the temperature on the electronic transport through a small group of molecular assembly system (MAS). The model involves two 1,4-dithiolbenzene (DTB) molecular units stacked in one dimension (1D). The currentvoltage (I-V) and the conductance voltage (G-V) analysis are presented under the influence of the temperature associated with the π-orbital coupling interactions controlled by the intermolecular spacingd. TheMASwith reduceddaffects significantly the conductance which results in reducing the conductance gap and the saturation voltageVsat. In addition, the present results show that the temperature rise effect plays an important role in determining the current flow in the saturation region. In this region, it is important to note thatVsatincreases linearly whenTgoes from 50 to 325 K.. To conclude,Vsatcan be controlled either by changing the temperature or modifying its intermolecular spacing conformation.

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Temperature Effect on Phase-Transition Radiation of Water

Journal of Heat Transfer ◽

10.1115/1.4026556 ◽

2014 ◽

Vol 136 (6) ◽

Cited By ~ 1

Author(s):

M. Q. Brewster ◽

K.-T. Wang ◽

W.-H. Wu ◽

M. G. Khan

Keyword(s):

Phase Transition ◽

Phase Change ◽

Temperature Dependence ◽

Transition Probability ◽

Cloud Droplet ◽

Radiation Absorption ◽

Effect Of Temperature ◽

Strong Temperature Dependence ◽

Atmospheric Windows ◽

Radiative Phase

Infrared radiation associated with vapor-liquid phase transition of water is investigated using a suspension of cloud droplets and mid-infrared (IR) (3–5 μm) radiation absorption measurements. Recent measurements and Monte Carlo (MC) modeling performed at 60 °C and 1 atm resulted in an interfacial radiative phase-transition probability of 5 × 10−8 and a corresponding surface absorption efficiency of 3–4%, depending on wavelength. In this paper, the measurements and modeling have been extended to 75 °C in order to examine the effect of temperature on water's liquid-vapor phase-change radiation. It was found that the temperature dependence of the previously proposed phase-change absorption theoretical framework by itself was insufficient to account for observed changes in radiation absorption without a change in cloud droplet number density. Therefore, the results suggest a strong temperature dependence of cloud condensation nuclei (CCN) concentration, i.e., CCN increasing approximately a factor of two from 60 °C to 75 °C at near saturation conditions. The new radiative phase-transition probability is decreased slightly to 3 × 10−8. Theoretical results were also calculated at 50 °C in an effort to understand behavior at conditions closer to atmospheric. The results suggest that accounting for multiple interface interactions within a single droplet at wavelengths in atmospheric windows (where anomalous IR radiation is often reported) will be important. Modeling also suggests that phase-change radiation will be most important at wavelengths of low volumetric absorption, i.e., atmospheric windows such as 3–5 μm and 8–10 μm, and for water droplets smaller than stable cloud droplet sizes (<20 μm diameter), where surface effects become relatively more important. This could include unactivated, hygroscopic aerosol particles (not CCN) that have absorbed water and are undergoing dynamic evaporation and condensation. This mechanism may be partly responsible for water vapor's IR continuum absorption in these atmospheric windows.

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STUDY OF MOLECULAR MOTIONS IN TWO LIQUID CRYSTAL FORMING COMPOUNDS EMPLOYING PLS

International Journal of Modern Physics B ◽

10.1142/s0217979206033814 ◽

2006 ◽

Vol 20 (14) ◽

pp. 2019-2034 ◽

Cited By ~ 1

Author(s):

K. CHANDRAMANI SINGH ◽

M. SHARMA ◽

P. C. JAIN

Keyword(s):

Liquid Crystal ◽

Temperature Dependence ◽

Liquid Crystalline ◽

Positron Lifetime ◽

Strong Temperature Dependence ◽

Molecular Motions ◽

Temperature Dependent ◽

Slow Cooling ◽

Positron Lifetime Spectroscopy ◽

Motion Studies

Results of molecular motion studies carried out in two liquid crystal forming compounds n-p-cyano-p-hexyloxybiphenyl (M18) and n-p-ethoxybenzylidene-p-butylaniline (EBBA) using positron lifetime spectroscopy (PLS) are presented. Temperature dependent positron lifetime measurements have been performed in each compound during the heating cycle of samples prepared by either quenching or slow cooling from the respective liquid crystalline phase of the compounds. In both the compounds, behaviors of the quenched and slow cooled samples are found to be different. The material in the quenched sample, unlike the slow-cooled sample, exhibits strong temperature dependence before it undergoes a glass transition. In each case, the temperature dependence of o-Ps pick-off lifetime in the quenched sample shows broad peaks at various characteristic temperatures. These peaks have been attributed to various intra- and inter-molecular motions associated with these compounds. The characteristic frequencies of some of the modes observed in the present work agree well with the literature reported values obtained from FIR and Raman studies. The present study demonstrates the usefulness of PLS in the study of molecular motions.

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