- 标题
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Self-propelled water droplet movement on a laser-etched radial gradient copper surface
摘要： This paper reports the behavior of water droplets on a topography-based, radial gradient on a metallic surface. The radial gradient was designed to concentrate water in the center region through the spontaneous motion and coalescence of individual droplets on the gradient pattern. In this work, parallel microchannels having a fixed width (~25 μm) and depth (100 μm) but variable spacing were used to impart a net surface tension force to the droplet for actuation. The diameter of the radial gradient (i.e. circular test region) was approximately 18.9 mm (or, ~0.75 in.). The surfaces were fabricated using a 355 nm YVO4 laser system and then characterized using droplet injection (5–38 μL) and spray testing techniques. Injected droplets were observed to move spontaneously away from the hydrophobic outer ring region of the circle towards the hydrophilic center as designed by the gradient. Droplet travel distances as large as 4 mm were measured depending on the droplet volume and injection site location. In application, such a design could be useful for promoting droplet coalescence on a surface and subsequently removal by gravity through the formation of sufficiently large droplets from two or more otherwise small droplets.
关键词： Surface tension gradient,Microchannels,Condensation,Heat exchangers,Radial pattern,Laser etching,Water droplet
更新于2025-09-23 15:21:01
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Data on eosin Y solutions for laser-induced fluorescence in water flows
摘要： Dye tracing techniques involve the tagging of a sample of water with dye, providing important qualitative and quantitative information. This article presents physical and fluorescence properties of dye solutions obtained by diluting a pharmaceutical aqueous solution of eosin Y with distilled water. Sample solutions with eosin concentrations ranging from 0 to 20 g/L were examined under various temperatures and laser powers. The data include measurements of dynamic viscosity, surface tension and pH. Fluorescence emission spectra as well as laser beam attenuation and photobleaching measurements are also reported. The datasets provide guidelines for obtaining optimal dye mixtures and suitable optical configurations to implement eosin fluorescence techniques.
关键词： Dye-water solution,Surface tension,Viscosity,Laser-induced fluorescence,pH
更新于2025-09-23 15:19:57
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Microhole Formation Behavior of Polypropylene Film Using CO<sub>2 </sub>Laser Irradiation
摘要： Biaxially oriented polypropylene films produced by simultaneous equi-biaxial stretching to the draw ratio of 4 (cid:186) 4 were perforated by the carbon dioxide laser under various laser fluences up to 426.3 J/cm2. After applying various laser fluences, the irradiated area was observed using a laser scanning confocal microscope. With the increase of fluence, the surface deformation with the formation of a crater surrounded by a doughnut-like rim was firstly observed at the laser fluence of 49.7 J/cm2, followed by the starting of the formation of a microhole surrounded by the rim at 113.7 J/cm2. The diameter of the microhole and the size of the rim increased rapidly with the increase of laser fluence. Mechanisms for the formation of a crater, the opening of a microhole, and the formation of surrounding rim were considered to be related to the surface tension and the shrinkage caused by molecular orientation relaxation. On the other hand, volume loss from the laser irradiated area was negligibly small at the moment of microhole opening, and started to increase rapidly when the fluence reached around 150 J/cm2. The microhole formation behavior was also observed by a high-speed camera. The velocity of microhole opening increased rapidly at first, presumably during the laser irradiation, and then slowed down after the cessation of laser irradiation. Theoretically estimated temperature distribution along the film thickness was compared with the laser perforation behavior. Starting of the deformation of film matched well with the starting of melting of the film surface. Film temperature was lower than the thermal decomposition temperature at the moment of the opening of a microhole, whereas at the moment of the starting of volume loss, film temperature was lower than the decomposition temperature estimated based on the heating rate of laser irradiated area, indicating that the decomposition and vaporization continues for a while after the cessation of laser irradiation.
关键词： microhole formation,molecular orientation relaxation,Polypropylene,laser fluence,CO2 laser,surface tension
更新于2025-09-19 17:13:59
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Influence of surface tension on the molten pool morphology in laser melting
摘要： The surface tension plays an important role in the distribution and evolution of molten pool morphology during laser melting. In this paper, based on the theory of Smoothed Particles Hydrodynamics (SPH), a mathematical model of surface tension on the molten pool morphology is established with the temperature change of molten pool being taken into account. The longitudinal morphology of molten pool and its formation process are simulated by using the SPH method under certain processing parameters, and the distributions of length and depth of molten pool are thoroughly analyzed at various processing parameters. The result shows that the longitudinal morphology of molten pool varying along the longitudinal section of solidified track presents a curve due to the influence of surface tension. A strong influence of Marangoni force on the flow of liquid metal and transformation of heat is also found. Moreover, the longitudinal morphology of a molten pool looks like that of a wave in the simulation; the deformation distributions of the longitudinal morphology of molten pool will increase with increasing laser power or decreasing scanning speed. The longitudinal morphologies of solidified molten pool are observed in the current experiments, and the experimental results are found to be agreed well with the calculated ones.
关键词： Processing parameters,Laser melting,Smoothed particles hydrodynamics (SPH),Molten pool morphology,Surface tension
更新于2025-09-16 10:30:52
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Analysis of surface tension driven flow and solidification behavior in laser linear welding of stainless steel
摘要： A transient three-dimensional thermal-?uid-metallurgy model was proposed to study the surface tension driven ?ow and welding metallurgical behavior during laser linear welding of 304 stainless steel. Numerical simulation and experimental method were both used to investigate the thermal behavior, surface tension driven ?ow, driving mechanism and solidi?cation characteristics. The temperature related driving force was qualitatively analyzed, and surface tension and surface shear stress were quantitatively studied. Numerical method and dimensional analysis were also carried out to understand the importance of di?erent driving forces, respectively. The metallurgical model was sequentially coupled to the thermal-?uid model to calculate four solidi?cation parameters. Temperature gradient was observed to be much larger at the front of the melt pool due to the e?ect of thermal conductivity, and decreased from center to the periphery. Both the surface tension and surface tension driven ?ow were found smaller in the central area. The maximum shear stress may reach 2500 N/m2 and pushed an intense outward convection. The solidi?cation parameters were used to predict the solidi?ed morphology, and the prediction was well validated by experimental results. The obtained basic conclusions in this work demonstrated that this study of thermal-?uid-metallurgical behavior could provide an improved understanding of the surface tension driven ?ow and solidi?cation behavior inside the melt pool of welding and additive manufacturing process.
关键词： Solidi?cation behavior,Surface tension,Driving force,Additive manufacturing,Fluid ?ow
更新于2025-09-12 10:27:22
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Size-controlled Patterning of Single-crystalline Perovskites Arrays toward Tunable High-performance Microlaser
摘要： Single-crystalline halide perovskites with regular morphology are of great significance for laser applications because they can be used to fabricate a natural whispering-gallery-mode resonator. Although enormous efforts have been put to synthesize single-crystalline perovskites, controlling the lateral size and thickness of the crystal, particularly at the nanoscale, is still challenging. Here, we report a facile and high-throughput strategy to selectively one-step create micro/nanoscale size-controlled all-inorganic perovskite single-crystal arrays by surface-tension-confined evaporative assembly. Our method can be used to easily tune the single crystal size and selectively position the single crystal, with versatility in fabricating perovskite single-crystal arrays in wafer scale. When the patterned size increases from 2 to 25 μm, the width of the CsPbClBr2 perovskite microplates increased from 150 nm to 4.2 μm. Fixing the width of the microplates at 1.6 μm, with the increase of the sliding speed from 50 to 250 mm/min, we could significantly control the thicknesses from 270 nm to 430 nm. Additionally, our present study provides a characterization of lasers based on different three-dimensional structures, confirming their width-dependence lasing mode and thickness-dependence lasing threshold characteristic, which is beneficial for the tunability of high-performance microlaser.
关键词： microlaser,surface-tension-confined,single crystal,halide-perovskite,evaporative assembly
更新于2025-09-12 10:27:22
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31.2: <i>Invited Paper:</i> Advanced Materials Development for Ink‐Jet Printed OLEDs
摘要： High-performance, ink-jet printable OLED materials have been successfully developed. Our wide libraries of platforms and small molecule hosts were effective for improving efficiency and lifetime of OLEDs. For wide color gamut, new emitters with deep in color and narrow full-width at half maximum were developed. Further, solvent systems having physical properties suitable for improving film uniformity in pixels were found.
关键词： Small molecule,FWHM,Viscosity,Red emitter,Surface tension,Platform,Film-uniformity,PLQY,Ink-jet,OLED
更新于2025-09-12 10:27:22
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[IEEE 2018 Iranian Conference on Electrical Engineering (ICEE) - Mashhad (2018.5.8-2018.5.10)] Electrical Engineering (ICEE), Iranian Conference on - Theoretical and Simulational Study of Electrowetting on Dielectric (EWOD) Effect
摘要： Electrowetting mechanism has been recently employed to enhance the manipulation process in biomedical engineering. In this research, we have described the Electrowetting on thermodynamic Dielectric phenomenon by using classical approach. The droplet motion has been numerically studied by finite element method. The electrowetting mechanism has been investigated by solving the coupled electrostatic and droplet physics. Simulation results revealed 50 V threshold voltage for the system. The droplet velocity increases linearly by increasing the applied electric field and the maximum velocity of 0.04 mm/s has been achieved for 250 V excitation voltage. Based on the results, for the above 250 V there is no velocity increases.
关键词： Digital microfluidics,Electrowetting,Contact angle,Electrowetting on dielectric (EWOD),Surface tension,hydrophobic layer
更新于2025-09-11 14:15:04
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Numerical Demonstration of In-Tube Liquid-Column Migration Driven by Photoisomerization
摘要： Droplet manipulation by light-induced isomerization was numerically demonstrated and investigated regarding the driving mechanism. Such a non-invasive manipulation of a droplet in a microchannel can be realized, for example, by the use of watery solution of photoresponsive surfactant that exhibits the isomerization. Due to variable fluid properties between the cis and trans isomers, one-side light irradiation on a liquid column in a tube would lead to some kind of imbalance between the two ends of the liquid column and then drive droplet migration. The present numerical simulations of air–liquid two-phase flow and its scalar transport of the isomer, considering the variable static contact angle, agreed quantitatively with the experimental results in terms of the migration speed. This fact supports the contention that the droplet migration is more likely to be driven by an imbalance in the wettability, or the contact angle. The migration speed was found to be less dependent on the liquid-column length, but proportional to the tube diameter.
关键词： photochemical reaction,non-invasive control,wettability,surface tension,microfluidics,computational fluid dynamics,lab-on-a-chip,droplet manipulation,two-phase flow,photoresponsible surfactant
更新于2025-09-09 09:28:46
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Printing Birefringent Figures by Surface Tension-Directed Self-Assembly of a Cellulose Nanocrystal/Polymer Ink Components
摘要： Photonic printing on transparent substrates using emerging synthetic photonic crystals is in high demand, especially for anti-fraud applications. However, photonic printing is faced with grand challenges including lack of the full invisibility of printed patterns before stimulation or after stimuli removal and absence of the long-lasting stability. Natural anisotropic crystal structures and artificially molecularly arranged polymers show an optically anisotropic property known as birefringence. Crystalline cellulose is the most abundant birefringent bio-crystal on the earth. Here, we introduce a printing method based on using a cellulose nanocrystal/polymer ink that is governed by surface evaporation phenomenon and divided surface tension forces to direct the self-assembly of ink components at the nanoscale and print 3D birefringent micro-figures on transparent substrates. This type of printing is from now on referred to as Birefringent Printing (BP). Unlike previously reported photonic crystal printing methods, this method is accurate, has high-contrast, is virtually impossible to forge and at the same time is very simple, inexpensive and non-toxic.
关键词： polymer ink,cellulose nanocrystal,directed self-assembly,birefringence,surface tension,invisible printing
更新于2025-09-04 15:30:14