scholarly journals Laser Induced Aggregation of Light Absorbing Particles by Marangoni Convection

2020 ◽  
Vol 10 (21) ◽  
pp. 7795
Author(s):  
Bo-Wei Li ◽  
Min-Cheng Zhong ◽  
Feng Ji
Keyword(s):  
Laser Heating ◽  
Laser Power ◽  
Convective Flow ◽  
Marangoni Convection ◽  
Photothermal Effect ◽  
Vapor Bubbles ◽  
Micro Particles ◽  
Particle Aggregate ◽  
Solution Layer ◽  
Induced Aggregation

Laser induced Marangoni convection can be used to accumulate micro-particles. In this paper, a method is developed to control and accumulate the light absorbing particles dispersed in a thin solution layer. The particles are irradiated by a focused laser beam. Due to the photothermal effect of the particles, the laser heating generates a thermal gradient and induces a convective flow around the laser’s heating center. The convective flow drives the particles to accumulate and form a particle aggregate close to the laser’s heating center. The motion of particles is dominated by the Marangoni convection. When the laser power is high, the vapor bubbles generated by laser heating on particles strengthen the convection, which accelerates the particles’ aggregation.

Acoustic Field-Assisted Two-Photon Polymerization Process

2021 ◽  
Vol 143 (10) ◽  
Author(s):  
Ketki M. Lichade ◽  
Yayue Pan
Keyword(s):  
Polymer Composite ◽  
Acoustic Field ◽  
Laser Power ◽  
Liquid Droplet ◽  
Three Dimensional ◽  
Polymerization Process ◽  
Photothermal Effect ◽  
Full Potential ◽  
Two Photon ◽  
Two Photon Polymerization

Abstract This study successfully integrates acoustic patterning with the Two-Photon Polymerization (TPP) process for printing nanoparticle–polymer composite microstructures with spatially varied nanoparticle compositions. Currently, the TPP process is gaining increasing attention within the engineering community for the direct manufacturing of complex three-dimensional (3D) microstructures. Yet the full potential of TPP manufactured microstructures is limited by the materials used. This study aims to create and demonstrate a novel acoustic field-assisted TPP (A-TPP) process, which can instantaneously pattern and assemble nanoparticles in a liquid droplet, and fabricate anisotropic nanoparticle–polymer composites with spatially controlled particle–polymer material compositions. It was found that the biggest challenge in integrating acoustic particle patterning with the TPP process is that nanoparticles move upon laser irradiation due to the photothermal effect, and hence, the acoustic assembly is distorted during the photopolymerization process. To cure acoustic assembly of nanoparticles in the resin through TPP with the desired nanoparticle patterns, the laser power needs to be carefully tuned so that it is adequate for curing while low enough to prevent the photothermal effect. To address this challenge, this study investigated the threshold laser power for polymerization of TPP resin (Pthr) and photothermal instability of the nanoparticle (Pthp). Patterned nanoparticle–polymer composite microstructures were fabricated using the novel A-TPP process. Experimental results validated the feasibility of the developed acoustic field-assisted TPP process on printing anisotropic composites with spatially controlled material compositions.

Surface Deformation and Thermal Convection in Electrostatically-Positioned Droplets Under Microgravity

1999 ◽  
Author(s):  
Suping Song ◽  
Ben Q. Li
Keyword(s):  
Surface Tension ◽  
Temperature Gradient ◽  
Laser Heating ◽  
Surface Deformation ◽  
Marangoni Convection ◽  
Stokes Equations ◽  
Energy Balance Equation ◽  
Droplet Surface ◽  
Fundamental Study ◽  
Recirculating Flow

Abstract Electrostatically positioned droplets are very useful for the fundamental study of solidification phenomena and the measurement of thermal physical properties. This paper descries a numerical analysis of surface deformation and surface tension driven flows in electrostatically positioned droplets in microgravity. The analysis is based on a fully coupled boundary element and finite element solution of the Maxwell equations, the Navier-Stokes equations and the energy balance equation. Results show that an applied electrostatic field results in a nonuniform electric stress distribution along the droplet surface, which, combined with surface tension, causes the droplet to deform into an ellipsoidal shape in microgravity. Laser heating induces a non-uniform temperature distribution in the droplet, which in turn produces Marangoni convection in the droplet. It is found that the viscous stress contribution to the deformation is small for a majority of cases. Also, a higher temperature gradient produces a stronger Marangoni convection in droplets with higher melting points that require more laser power. The internal recirculating flow may be reduced by more uniform laser heating. During the undercooling of the droplet, both temperature and fluid flow fields evolve in time such that the temperature gradient and the tangential velocities along the droplet surface subside in magnitude and reverse their directions.

Raman Scattering as a Temperature Frobe for Laser Heating of Si

1982 ◽  
Vol 17 ◽  
Author(s):  
Dimitry Kirillov ◽  
James L. Merz
Keyword(s):  
Raman Scattering ◽  
Laser Beam ◽  
Laser Heating ◽  
Laser Power ◽  
Raman Scattering Spectrum ◽  
Phonon Line ◽  
Cw Laser ◽  
Scattering Spectrum ◽  
Beam Heating ◽  
Laser Beam Heating

ABSTRACTThe frequency of the phonon line in the Raman scattering spectrum recorded during CW laser-beam heating of Si was used as a characteristic of the lattice temperature inside the laser spot. It is shown that Raman scattering is a good temperature probe up to the laser power approaching optical damage of Si.

scholarly journals Vascular disrupting agent induced aggregation of gold nanoparticles for photothermally enhanced tumor vascular disruption

2020 ◽  
Vol 6 (23) ◽  
pp. eabb0020 ◽  
Author(s):  
Sheng Hong ◽  
Di-Wei Zheng ◽  
Cheng Zhang ◽  
Qian-Xiao Huang ◽  
Si-Xue Cheng ◽  
...  
Keyword(s):  
Gold Nanoparticles ◽  
Tumor Growth ◽  
Tumor Therapy ◽  
Tumor Model ◽  
Vascular Damage ◽  
Photothermal Effect ◽  
Tumor Growth Inhibition ◽  
Vascular Disrupting Agent ◽  
Induced Aggregation ◽  
Vascular Disrupting

Although vascular disrupting agents (VDAs) have been extensively implemented in current clinical tumor therapy, the notable adverse events caused by long-term dosing severely limit the therapeutic efficacy. To improve this therapy, we report a strategy for VDA-induced aggregation of gold nanoparticles to further destroy tumor vascular by photothermal effect. This strategy could effectively disrupt tumor vascular and cut off the nutrition supply after just one treatment. In the murine tumor model, this strategy results in notable tumor growth inhibition and gives rise to a 92.7% suppression of tumor growth. Besides, enhanced vascular damage could also prevent cancer cells from distant metastasis. Moreover, compared with clinical therapies, this strategy still exhibits preferable tumor suppression and metastasis inhibition ability. These results indicate that this strategy has great potential in tumor treatment and could effectively enhance tumor vascular damage and avoid the side effects caused by frequent administration.

scholarly journals Gold Nanorod-Mediated Photothermal Modulation for Localized Ablation of Cancer Cells

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Yoochan Hong ◽  
Eugene Lee ◽  
Jihye Choi ◽  
Seung Jae Oh ◽  
Seungjoo Haam ◽  
...  
Keyword(s):  
Cancer Cells ◽  
Laser Power ◽  
Near Infrared ◽  
Gold Nanorod ◽  
Photothermal Effect ◽  
Transduction Efficiency ◽  
Dead Cell ◽  
Photothermal Ablation ◽  
Power Densities ◽  
Nir Laser

We estimated the photothermal transduction efficiency of gold nanorod (GNR) solutions for different GNR concentrations and irradiation laser power. In particular, we verified that the degree of cell death area could be modulated by GNR concentration and irradiation laser power. The efficacy of GNR-produced photothermal ablation of cancer cells was evaluated by irradiating GNRs in the presence of MDA-MB-231 breast cancer cells with a near-infrared (NIR) laser at different laser power densities and irradiation times. GNR-induced photothermal ablation was applied successfully to cancer cells at various NIR laser power densities and irradiation times and was characterized with live-dead cell staining. Through these techniques, we established the system for not only verification of induced photothermal effect using NIR laser and thermocouple, but also identification of uptake efficiency for GNRs and cell viability using dark field and fluorescence imaging, respectively.

Microstructural Modification of Laser-Bent Open-Cell Aluminum Foams

2012 ◽  
Vol 504-506 ◽  
pp. 1213-1218 ◽  
Author(s):  
Loredana Santo ◽  
Denise Bellisario ◽  
Ludovica Rovatti ◽  
Fabrizio Quadrini
Keyword(s):  
Laser Heating ◽  
Laser Power ◽  
Laser Forming ◽  
Processing Conditions ◽  
Aluminum Foams ◽  
Laser Bending ◽  
Bending Angle ◽  
Open Cell ◽  
Scan Rate ◽  
Alloy Microstructure

Laser forming tests have been performed on open-cell aluminum alloy foams with different pore size. Laser power was fixed at 150 W, a total of 150 laser scans led to a bending angle up to 60°, depending on the laser scan rate. At the end of the laser bending, the foams were left to cool and samples were extracted for analysis by means of an optic microscope. The alloy microstructure was investigated in different points of the samples and correlated with the processing conditions. Image analysis was also carried out to extract the percentage of melted area due to laser heating.

Thermal effects on the Raman spectra of nanodiamonds

2011 ◽  
Vol 1282 ◽  
Author(s):  
Marc Chaigneau ◽  
Hugues A. Girard ◽  
Jean-Charles Arnault ◽  
Razvigor Ossikovski
Keyword(s):  
Raman Spectra ◽  
Thermal Effects ◽  
Laser Heating ◽  
Quantum Confinement ◽  
Laser Power ◽  
Heating Effect ◽  
Scattering Experiment ◽  
Quantum Confinement Effects ◽  
High Pressure High Temperature ◽  
Peak Assignment

ABSTRACTWe report on the influence of the laser heating effect, potentially present in a Raman scattering experiment, on the behaviour of carbon phonon lines in the spectra of nanodiamond particles. Aside from the laser power used in the experiment, the extent of the thermal effect in question depends also on the nanodiamonds origin (obtained through detonation and high pressure high temperature techniques) as well as on the nanoparticles size. Laser heating should be properly taken into account when discussing Raman spectra of carbonaceous species, in particular, prior to addressing peak assignment and possible quantum confinement effects.

Production of Calcium Phosphate Particles from Marine Wastes by Gas Jet Assisted Laser Heating

2008 ◽  
Vol 587-588 ◽  
pp. 497-501
Author(s):  
F. Lusquiños ◽  
M. Boutinguiza ◽  
R. Comesaña ◽  
A. Riveiro ◽  
F. Quintero ◽  
...  
Keyword(s):  
Calcium Phosphate ◽  
Laser Heating ◽  
Gas Flow ◽  
Fine Particles ◽  
Fish Bone ◽  
Heating Method ◽  
Metallic Particles ◽  
Micro Particles ◽  
Calcium Phosphate Particles ◽  
Manufacturing Techniques

There are many manufacturing techniques to form metallic particles with certain size and properties. The laser heating method has been successfully applied to generate metallic particles when a supersonic gas flow is assisting this process. The metallic target is heated, melted and vaporised and micro-particles are carried away by a gas flow stream. The high-velocity gas is used to solidificate molten particles and to condensate the metallic vapour resulting in the formation of fine particles. Several attempts were carried out for the production of metallic particles by laser supersonic heating method, obtaining spherical micro-particles (1- 50 "m) of copper, steel, or aluminium. This work presents the application of this method to generate particles from fish bone, in order to obtain a material with a composition close to the inorganic part of the bones. A pulsed Nd:YAG laser has been used to obtain calcium phosphate micro- and nanoparticles. Microparticles size ranges from 10 to 100"m, whereas the nanoparticles have diameters as small as 2 nm. High resolution transmission electron microscopy (HRTEM) allowed us to identify the nanoparticles as whitlockite.

Red shifted-Photoluminescence of Ensembles of GaN Nano-Crystallites

2003 ◽  
Vol 776 ◽  
Author(s):  
Leah Bergman ◽  
Xiang-Bai Chen ◽  
Joel Feldmeier ◽  
Andrew P. Purdy
Keyword(s):  
Thin Film ◽  
Laser Heating ◽  
Laser Power ◽  
Scattered Light ◽  
Optical Analysis ◽  
Ensemble Size ◽  
Nano Crystalline ◽  
Heating Event ◽  
Small Ensemble ◽  
Cubic Structure

AbstractWe present optical analysis concerning the redshift of the photoluminescence (PL) of ensembles of GaN nano-crystals. We found that the extent of the redshift depends on the laser power as well as on the ensemble size. For ensemble of size ∼ 30 μm, the laser power in our experimental specification impacted the PL energy and caused a redshift of up to 120 meV. This phenomena was not observed for a small ensemble of ∼ 1 νm or less. For the small ensemble the PL redshift was negligible and depended weakly on the laser power; similar behavior was found in GaN thin film. The above findings were observed in the PL of GaN nano-crystalline of Wurtzite as well as cubic structure. Our results point to a laser heating event occurring in the large ensemble; the emitted and scattered light is confined among the nano-crystallites thus causing the heating. For a small ensemble the light has a higher probability of diffusing outside the enclosure, and thus no laser heating occurs.

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