Understanding desiccation patterns of blood sessile drops

2017 ◽  
Vol 5 (45) ◽  
pp. 8991-8998 ◽  
Author(s):  
Ruoyang Chen ◽  
Liyuan Zhang ◽  
Duyang Zang ◽  
Wei Shen
Keyword(s):  
Sessile Drop ◽  
Formation Mechanisms ◽  
Sessile Drops

Formation mechanisms of cracking patterns in different regions of a desiccation blood sessile drop.

The shape evolution of liquid droplets in miscible environments

2018 ◽  
Vol 852 ◽  
pp. 422-452 ◽  
Author(s):  
Daniel J. Walls ◽  
Eckart Meiburg ◽  
Gerald G. Fuller
Keyword(s):  
Sessile Drop ◽  
Liquid Droplet ◽  
Leading Edge ◽  
Numerical Approach ◽  
Shape Evolution ◽  
Liquid Droplets ◽  
Miscible Liquids ◽  
Experimental Findings ◽  
Sessile Drops ◽  
Pendant Drops

Miscible liquids often come into contact with one another in natural and technological situations, commonly as a drop of one liquid present in a second, miscible liquid. The shape of a liquid droplet present in a miscible environment evolves spontaneously in time, in a distinctly different fashion than drops present in immiscible environments, which have been reported previously. We consider drops of two classical types, pendant and sessile, in building upon our prior work with miscible systems. Here we present experimental findings of the shape evolution of pendant drops along with an expanded study of the spreading of sessile drops in miscible environments. We develop scalings considering the diffusion of mass to group volumetric data of the evolving pendant drops and the diffusion of momentum to group leading-edge radial data of the spreading sessile drops. These treatments are effective in obtaining single responses for the measurements of each type of droplet, where the volume of a pendant drop diminishes exponentially in time and the leading-edge radius of a sessile drop grows following a power law of $t^{1/2}$ at long times. A complementary numerical approach to compute the concentration and velocity fields of these systems using a simplified set of governing equations is paired with our experimental findings.

Non-isolated drop impact on surfaces

2017 ◽  
Vol 835 ◽  
pp. 24-44 ◽  
Author(s):  
Y. Wang ◽  
L. Bourouiba
Keyword(s):  
Momentum Transfer ◽  
Impact Velocity ◽  
Solid Surface ◽  
Weber Number ◽  
Sessile Drop ◽  
Impact Force ◽  
New Paradigm ◽  
Existence Conditions ◽  
Secondary Droplets ◽  
Sessile Drops

Upon impact on a solid surface, a drop expands into a sheet, a corona, which can rebound, stick or splash and fragment into secondary droplets. Previously, focus has been placed on impacts of single drops on surfaces to understand their splash, rebound or spreading. This is important for spraying, printing, and environmental and health processes such as contamination by pathogen-bearing droplets. However, sessile drops are ubiquitous on most surfaces and their interaction with the impacting drop is largely unknown. We report on the regimes of interactions between an impacting drop and a sessile drop. Combining experiments and theory, we derive the existence conditions for the four regimes of drop–drop interaction identified, and report that a subtle combination of geometry and momentum transfer determines a critical impact force governing their physics. Crescent-moon fragmentation is most efficient at producing and projecting secondary droplets, even when the impacting drop Weber number would not allow for splash to occur on the surface considered if the drop were isolated. We introduce a critical horizontal impact Weber number $We_{c}$ that governs the formation of a sheet from the sessile drop upon collision with the expanding corona of the impacting drop. We also predict and validate important properties of the crescent-moon fragmentation: the extension of its sheet base and the ligaments surrounding its base. Finally, our results suggest a new paradigm: impacts on most surfaces can make a splash of a new kind – a crescent-moon – for any impact velocity when neighbouring sessile drops are present.

Heat Transfer and Flow Instabilities in Ethanol Sessile Drops Under Evaporation

2010 ◽  
Author(s):  
Benjamin Sobac ◽  
David Brutin
Keyword(s):  
Heat Transfer ◽  
Sessile Drop ◽  
Scaling Law ◽  
Video Recording ◽  
Infrared Camera ◽  
Theoretical Work ◽  
Evaporation Process ◽  
Drop Evaporation ◽  
Space Resolution ◽  
Sessile Drops

Thanks to a recent increase in space resolution and temperature accuracy of infrared camera device, it’s now possible to perform thermal visualizations of sessile drops under evaporation. Using infrared techniques, we can access local thermal motions inside millimetric drops without perturbing the internal mechanisms. In the full paper, we will provide a literature review of experimental, numerical simulation and theoretical work recently perform on sessile drop evaporation. We will also detail the experimental setup which has been elaborated to realize these thermal observations. Using infrared and visible video recording, we can follow respectively the evolution of the motion inside the drop and the drop shape during evaporation. Using a heat fluxmeter placed below the drop, we can analyze the heat transfer between the substrate and the drop. We will completely describe the evaporation process based on a reference experiment and evidence the existence of several phases during this process. Then, we will dwell on the heat flux transferred to the drop during each step of the evaporation process to obtain very important information about the coupling between flow motion and heat transfer coefficient. Finally, we will present the influence of substrate temperature and drop size on the evaporation process which leads us to build a scaling law and better understand drop evaporation process.

Surface and interfacial tensions from the profile of a sessile drop

1972 ◽  
Vol 329 (1579) ◽  
pp. 421-431 ◽  
Keyword(s):  
Thin Film ◽  
Correction Factor ◽  
Sessile Drop ◽  
Maximum Height ◽  
Gravitational Acceleration ◽  
Interfacial Tensions ◽  
Two Fluids ◽  
Intermediate Size ◽  
Surrounding Fluid ◽  
Sessile Drops

Sessile drops and captive bubbles resting at a plane solid surface but separated from the surface by a thin film of the surrounding fluid, appear to possess angles of contact of 180°. The limiting height, Z ∞ 180 of a very large sessile drop formed under these conditions is related to the interfacial tension, γ , by the expression γ = ¼∆ pg ( Z ∞ 180 ) 2 , where ∆ p is the density difference of the two fluids and g , the gravitational acceleration. As very large drops are not usually obtained experimentally the maximum height of a drop of intermediate size was measured and used in the equation with an appropriate correction factor. The correction factor was obtained from tables of the profiles of sessile drops. The correction factor is invariant for all values of γ , ∆ p and g . The method is tested experimentally and shown to agree with the results obtained by other methods for a number of widely differing systems. The reproducibility and sources of error are discussed.

Evaporative self-assembly of soft colloidal monolayers: The role of particle softness on microstructure

Soft Matter ◽  
2021 ◽  
Author(s):  
Merin Jose ◽  
Madivala G Basavaraj ◽  
Dillip Kumar Satapathy
Keyword(s):  
Self Assembly ◽  
Sessile Drop ◽  
Drop Evaporation ◽  
Microgel Particles ◽  
Sessile Drop Evaporation ◽  
Sessile Drops

We investigate the sessile drop evaporation aided self-assembly of microgel particles by varying their softness. Evaporation of sessile drops containing amphiphilic microgel particles at suitable concentrations results in uniform monolayer...

scholarly journals Correction to “Contact Angle of Sessile Drops in Lennard-Jones Systems”

2021 ◽  
Author(s):  
Stefan Becker ◽  
Herbert M. Urbassek ◽  
Martin Horsch ◽  
Hans Hasse
Keyword(s):  
Contact Angle ◽  
Interaction Energy ◽  
Sessile Drop ◽  
Solid Wall ◽  
Lennard Jones ◽  
Solid Density ◽  
Dynamics Simulations ◽  
Solid Liquid ◽  
Constant Contact Angle ◽  
Sessile Drops

Molecular dynamics simulations are used for studying the contact angle of nanoscale sessile drops on a planar solid wall in a system interacting via the truncated and shifted Lennard-Jones potential. The entire range between total wetting and dewetting is investigated by varying the solid–fluid dispersive interaction energy. The temperature is varied between the triple point and the critical temperature. A correlation is obtained for the contact angle in dependence of the temperature and the dispersive interaction energy. Size effects are studied by varying the number of fluid particles at otherwise constant conditions, using up to 150 000 particles. For particle numbers below 10 000, a decrease of the contact angle is found. This is attributed to a dependence of the solid–liquid surface tension on the droplet size. A convergence to a constant contact angle is observed for larger system sizes. The influence of the wall model is studied by varying the density of the wall. The effective solid–fluid dispersive interaction energy at a contact angle of θ = 90° is found to be independent of temperature and to decrease linearly with the solid density. A correlation is developed that describes the contact angle as a function of the dispersive interaction, the temperature, and the solid density. The density profile of the sessile drop and the surrounding vapor phase is described by a correlation combining a sigmoidal function and an oscillation term.

Thermal Patterns and Internal Flow Mechanisms in Evaporating Inverted Sessile Drops of Pure Water

2019 ◽  
Author(s):  
Tejaswi Josyula ◽  
Chandan Manghnani ◽  
Pallab Sinha Mahapatra ◽  
Arvind Pattamatta
Keyword(s):  
Contact Line ◽  
Sessile Drop ◽  
Pure Water ◽  
Maximum Velocity ◽  
Internal Flow ◽  
Industrial Applications ◽  
Marangoni Flow ◽  
Thermal Patterns ◽  
Contact Line Dynamics ◽  
Sessile Drops

Abstract We report an experimental investigation on contact line dynamics, thermal patterns, and internal fluid flow during the evaporation of inverted sessile drops of pure water. This configuration of sessile drop when placed on a heated substrate should lead to thermal stratification and any internal convective flow will be governed by surface tension driven Marangoni flow. First, we report contact line dynamics and thermal patterns recorded using an optical camera and infrared camera, respectively. An interesting outcome from the present study is the resemblance observed between the evolution of contact angle and interfacial temperature difference during evaporation. By performing Particle Image Velocimetry to delineate the internal flow characteristics, we report an axisymmetric counter-rotating flow inside the drop. This flow is directed towards the substrate from the apex at the centerline of the drop. In literature, a similar directional flow is reported to be due to Marangoni flow albeit for a normal sessile drop. Further, by extracting the magnitude of velocity, we report a maximum velocity in the flow occurring at the center of drop which in turn increases with substrate temperature. The results reported in the present study shed light on the presence of Marangoni flow in pure water drops whose understanding is of paramount importance in many academic and industrial applications.

scholarly journals Interface Reactions Responsible for Run-Out in Active Brazing: Part 3

2021 ◽  
Vol 100 (12) ◽  
pp. 379-395
Author(s):  
PAUL T. VIANCO ◽  
◽  
CHARLES A. WALKER ◽  
DENNIS DE SMET ◽  
ALICE KILGO ◽  
...  
Keyword(s):  
Reaction Layer ◽  
Chemical Potential ◽  
Filler Metal ◽  
Sessile Drop ◽  
Interface Reaction ◽  
Base Material ◽  
Mitigation Strategies ◽  
Interface Reactions ◽  
Rate Kinetics ◽  
Sessile Drops

This study examined the interface reaction between sessile drops of the Ag-xAl filler metals having x = 0.2, 0.5, and 1.0 wt-% and KovarTM base material as an avenue to understand the run-out phenomenon observed in active filler metal braze joints. The brazing conditions were combinations of 965°C (1769°F) and 995°C (1823°F) temperatures and brazing times of 5 and 20 min. All brazing was performed in a vacuum of 10–7 Torr. Microanalysis confirmed that a reaction layer developed ahead of the filler metal to support spontaneous wetting and spreading activity. However, run-out was not observed with the sessile drops because the additional surface energy created by the sessile drop free surface constrained wetting and spreading. The value of z in the reaction layer composition, (Fe, Ni, Co)yAlz, increased with x of the Ag-xAl sessile drops for both brazing conditions. Generally, the values of z were lower for the more severe brazing conditions. Also, the reaction layer thickness increased with the Al concentration in the filler metal but did not increase with the severity of brazing conditions. These behaviors indicate that the interface reaction was controlled by the chemical potential rather than the rate kinetics of a thermally activated process. The determining metrics were filler metal composition (Ag-xAl) and brazing temperature. The findings of the present study provided several insights toward developing potential mitigation strategies to prevent run-out.

scholarly journals Sessile volatile drop evaporation under microgravity

2020 ◽  
Vol 6 (1) ◽  
Author(s):  
Sanjeev Kumar ◽  
Marc Medale ◽  
Paolo Di Marco ◽  
David Brutin
Keyword(s):  
Evaporation Rate ◽  
Sessile Drop ◽  
Experimental Results ◽  
Sounding Rocket ◽  
Critical Height ◽  
Drop Evaporation ◽  
Capillary Instabilities ◽  
Volatile Liquids ◽  
Drop Interface ◽  
Sessile Drops

AbstractThe evaporation of sessile drops of various volatile and non-volatile liquids, and their internal flow patterns with or without instabilities have been the subject of many investigations. The current experiment is a preparatory one for a space experiment planned to be installed in the European Drawer Rack 2 (EDR-2) of the International Space Station (ISS), to investigate drop evaporation in weightlessness. In this work, we concentrate on preliminary experimental results for the evaporation of hydrofluoroether (HFE-7100) sessile drops in a sounding rocket that has been performed in the frame of the MASER-14 Sounding Rocket Campaign, providing the science team with the opportunity to test the module and perform the experiment in microgravity for six consecutive minutes. The focus is on the evaporation rate, experimentally observed thermo-capillary instabilities, and the de-pinning process. The experimental results provide evidence for the relationship between thermo-capillary instabilities and the measured critical height of the sessile drop interface. There is also evidence of the effects of microgravity and Earth conditions on the sessile drop evaporation rate, and the shape of the sessile drop interface and its influence on the de-pinning process.

The dislocation structure of a 10° [110] tilt boundary in silicon

1983 ◽  
Vol 41 ◽  
pp. 114-115
Author(s):  
B. Cunningham ◽  
D.G. Ast
Keyword(s):  
Dislocation Structure ◽  
Tilt Angle ◽  
Imaging Technique ◽  
Diamond Lattice ◽  
Tilt Boundary ◽  
Formation Mechanisms ◽  
Diffraction Contrast ◽  
Lattice Fringe ◽  
Tilt Boundaries ◽  
Chemically Vapor Deposited

There have Been a number of studies of low-angle, θ < 4°, [10] tilt boundaries in the diamond lattice. Dislocations with Burgers vectors a/2<110>, a/2<112>, a<111> and a<001> have been reported in melt-grown bicrystals of germanium, and dislocations with Burgers vectors a<001> and a/2<112> have been reported in hot-pressed bicrystals of silicon. Most of the dislocations were found to be dissociated, the dissociation widths being dependent on the tilt angle. Possible dissociation schemes and formation mechanisms for the a<001> and a<111> dislocations from the interaction of lattice dislocations have recently been given.The present study reports on the dislocation structure of a 10° [10] tilt boundary in chemically vapor deposited silicon. The dislocations in the boundary were spaced about 1-3nm apart, making them difficult to resolve by conventional diffraction contrast techniques. The dislocation structure was therefore studied by the lattice-fringe imaging technique.

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