Uniform and Gaussian Ultraviolet Light Intensity Distribution on Droplet for Selective Area Deposition of Particles

2020 ◽  
Vol 142 (9) ◽  
Author(s):  
Tianyi Li ◽  
Aravinda Kar ◽  
Ranganathan Kumar
Keyword(s):  
Contact Line ◽  
Sessile Drop ◽  
Uv Light ◽  
Incident Light ◽  
Droplet Surface ◽  
Light Distribution ◽  
Surface Tension Gradient ◽  
Sessile Droplet ◽  
Selective Area ◽  
Light Profiles

Abstract Particle transport through Marangoni convection inside a sessile droplet can be controlled by the ultraviolet (UV) light distribution on the surface. The photosensitive solution changes the surface tension gradient on the droplet surface and can induce clockwise and counterclockwise circulations depending on the incident light distribution. In this paper, the stream function in the sessile drop has been evaluated in toroidal coordinates by solving the biharmonic equation. Multiple primary clockwise and counterclockwise circulations are observed in the droplet under various concentric UV light profiles. The downward dividing streamlines are expected to deposit the particles on the substrate, thus matching the number of deposited rings on the substrate with the number of UV light rings. Moffatt eddies appear near the contact line or centerline of the droplet depending on the UV light profile and its distance from the contact line.

Uniform and Gaussian UV Light Intensity Distribution on Droplet for Selective Area Deposition of Particles

2020 ◽  
Author(s):  
Tianyi Li ◽  
Aravinda Kar ◽  
Ranganathan Kumar
Keyword(s):  
Sessile Drop ◽  
Uv Light ◽  
Incident Light ◽  
Droplet Surface ◽  
Light Distribution ◽  
Surface Tension Gradient ◽  
Sharp Change ◽  
Sessile Droplet ◽  
Selective Area ◽  
Light Profiles

Abstract Particle transport through Marangoni convection inside a sessile droplet can be controlled by the UV light distribution on the surface. The photosensitive solution changes the surface tension gradient on the droplet surface and can induce clockwise and counter-clockwise circulations depending on the incident light distribution. In this paper, the stream function in the sessile drop has been evaluated in toroidal coordinates by solving the biharmonic equation. Multiple primary clockwise and counter-clockwise circulations are observed in the droplet under various concentric UV light profiles. The downward dividing streamlines are expected to deposit the particles on the substrate, thus matching the number of deposited rings on the substrate with the number of UV light rings. Moffatt eddies appear near the contact line or centerline of the droplet either due to a sharp change in the UV light profile or because the illuminated region is away from them.

Marangoni circulation by UV light modulation on sessile drop for particle agglomeration

2019 ◽  
Vol 873 ◽  
pp. 72-88 ◽  
Author(s):  
Tianyi Li ◽  
Aravinda Kar ◽  
Ranganathan Kumar
Keyword(s):  
Stokes Flow ◽  
Particle Deposition ◽  
Sessile Drop ◽  
Uv Light ◽  
Surface Tension Gradient ◽  
Light Modulation ◽  
Particle Agglomeration ◽  
On Demand ◽  
Toroidal Coordinates ◽  
Corner Flows

An analytical solution of a biharmonic equation is presented in axisymmetric toroidal coordinates for Stokes flow due to surface tension gradient on the free surface of sessile drops. The stream function profiles exhibit clockwise and counter-clockwise toroidal volumes. The ring or dot formed by the downward dividing streamlines between these volumes predicts the experimentally deposited particle ring or dot well. This finding suggests that the downward dividing streamline can be taken to be a reasonable indicator of where deposition occurs. Different light patterns directed at different locations of the droplet can give rise to a single spot or ring. A relationship between the positions of the light intensity peak and possible locations of particle deposition is analysed to demonstrate that the streamlines can be generated on-demand to achieve particle deposition at predetermined locations on the substrate. Toroidal corner vortices called Moffatt eddies have appeared in other corner flows and develop in this optical Marangoni flow as well near the contact line.

scholarly journals Self-Sorting of Bidispersed Colloidal Particles Near Contact Line of an Evaporating Sessile Droplet

Langmuir ◽  
2018 ◽  
Vol 34 (40) ◽  
pp. 12058-12070 ◽  
Author(s):  
Nagesh D. Patil ◽  
Rajneesh Bhardwaj ◽  
Atul Sharma
Keyword(s):  
Contact Line ◽  
Colloidal Particles ◽  
Sessile Droplet

scholarly journals Atmospheric aerosol attenuation effect on FD data analysis at the Pierre Auger Observatory

2019 ◽  
Vol 210 ◽  
pp. 05008
Author(s):  
Laura Valore ◽  
Keyword(s):  
Atmospheric Aerosol ◽  
Uv Light ◽  
Pierre Auger Observatory ◽  
Event Analysis ◽  
Air Showers ◽  
Fluorescence Detector ◽  
Attenuation Effect ◽  
Laser Facility ◽  
Shower Maximum ◽  
Light Profiles

The atmospheric aerosol monitoring system of the Pierre Auger Observatory has been operating smoothly since 2004. Two laser facilities (Central Laser Facility, CLF and eXtreme Laser Facility, XLF) fire sets of 50 shots four times per hour during FD shifts to measure the highly variable hourly aerosol attenuation to correct the longitudinal UV light profiles of the Extensive Air Showers detected by the Fluorescence Detector. Hourly aerosol attenuation loads (Vertical Aerosol Optical Depth) are used to correct the measured profiles. Two techniques are used to determine the aerosol profiles, which have been proven to be fully compatible. The uncertainty in the VAOD profiles measured consequently leads to an uncertainty on the energy and on the estimation of the depth at the maximum development of a shower (Xmax) of the event in analysis. To prove the validity of the aerosol attenuation measurements used in FD event analysis, the flatness of the ratio of reconstructed SD to FD energy as a function of the aerosol transmission to the depth of shower maximum has been verified.

scholarly journals Photooxidation of Cyclohexane by Visible and Near-UV Light Catalyzed by Tetraethylammonium Tetrachloroferrate

Catalysts ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 403
Author(s):  
Kira Fahy ◽  
Adam Liu ◽  
Kelsie Barnard ◽  
Valerie Bright ◽  
Robert Enright ◽  
...  
Keyword(s):  
Acetic Acid ◽  
Reaction Rate ◽  
Uv Light ◽  
Incident Light ◽  
Reaction Conditions ◽  
Primary Products ◽  
Photonic Efficiency ◽  
Quenching By Oxygen

Tetraethylammonium tetrachloroferrate catalyzes the photooxidation of cyclohexane heterogeneously, exhibiting significant photocatalysis even in the visible portion of the spectrum. The photoproducts, cyclohexanol and cyclohexanone, initially develop at constant rates, implying that the ketone and the alcohol are both primary products. The yield is improved by the inclusion of 1% acetic acid in the cyclohexane. With small amounts of catalyst, the reaction rate increases with the amount of catalyst employed, but then passes through a maximum and decreases, due to increased reflection of the incident light. The reaction rate also passes through a maximum as the percentage of dioxygen above the sample is increased. This behavior is due to quenching by oxygen, which at the same time is a reactant. Under one set of reaction conditions, the photonic efficiency at 365 nm was 0.018 mol/Einstein. Compared to TiO2 as a catalyst, Et4N[FeCl4] generates lower yields at wavelengths below about 380 nm, but higher yields at longer wavelengths. Selectivity for cyclohexanol is considerably greater with Et4N[FeCl4], and oxidation does not proceed past cyclohexanone.

scholarly journals Electrically-Tunable Blue Phase Liquid Crystal Microlens Array Based on a Photoconductive Film

Polymers ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 65 ◽  
Author(s):  
Bing-Yau Huang ◽  
Shuan-Yu Huang ◽  
Chia-Hsien Chuang ◽  
Chie-Tong Kuo
Keyword(s):  
Refractive Index ◽  
Liquid Crystal ◽  
Electric Field ◽  
Uv Light ◽  
Focal Length ◽  
Incident Light ◽  
Microlens Array ◽  
Gradient Distribution ◽  
Phase Liquid ◽  
Blue Phase

This paper proposes an effective approach to fabricate a blue phase liquid crystal (BPLC) microlens array based on a photoconductive film. Owing to the characteristics of photo-induced conducting polymer polyvinylcarbazole (PVK), in which conductivity depends on the irradiation of UV light, a progressive mask resulting in the variation of conductivity is adopted to produce the gradient distribution of the electric field. The reorientations of liquid crystals according to the gradient distribution of the electric field induce the variation of the refractive index. Thus, the incident light experiences the gradient distribution of the refractive index and results in the focusing phenomenon. The study investigates the dependence of lens performance on UV exposure time, the focal length of the lens, and focusing intensities with various incident polarizations. The BPLC microlens array exhibits advantages such as electrically tunability, polarization independence, and fast response time.

scholarly journals Prediction of Contact Angle of Nanofluids by Single-Phase Approaches

Energies ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 4558 ◽  
Author(s):  
Nur Çobanoğlu ◽  
Ziya Haktan Karadeniz ◽  
Patrice Estellé ◽  
Raul Martínez-Cuenca ◽  
Matthias H. Buschmann
Keyword(s):  
Contact Angle ◽  
Single Phase ◽  
Substrate Surface ◽  
Droplet Surface ◽  
Force Balance ◽  
Radius Of Curvature ◽  
Geometrical Parameters ◽  
Ambient Conditions ◽  
Sessile Droplet ◽  
Droplet Shape

Wettability is the ability of the liquid to contact with the solid surface at the surrounding fluid and its degree is defined by contact angle (CA), which is calculated with balance between adhesive and cohesive forces on droplet surface. Thermophysical properties of the droplet, the forces acting on the droplet, atmosphere surrounding the droplet and the substrate surface are the main parameters affecting on CA. With nanofluids (NF), nanoparticle concentration and size and shape can modify the contact angle and thus wettability. This study investigates the validity of single-phase CA correlations for several nanofluids with different types of nanoparticles dispersed in water. Geometrical parameters of sessile droplet (height of the droplet, wetting radius and radius of curvature at the apex) are used in the tested correlations, which are based on force balance acting on the droplet surface, energy balance, spherical dome approach and empirical expression, respectively. It is shown that single-phase models can be expressed in terms of Bond number, the non-dimensional droplet volume and two geometrical similarity simplexes. It is demonstrated that they can be used successfully to predict CA of dilute nanofluids’ at ambient conditions. Besides evaluation of CA, droplet shape is also well predicted for all nanofluid samples with ±5% error.

Nanoparticle Motion and Deposition Pattern From Evaporating Binary Droplets

2016 ◽  
Author(s):  
Xin Zhong ◽  
Fei Duan
Keyword(s):  
Flow Field ◽  
Binary Solution ◽  
Central Area ◽  
Droplet Surface ◽  
Sessile Droplet ◽  
Deposition Pattern ◽  
Fluorescent Microspheres ◽  
Nanoparticle Deposition ◽  
Image Velocimetry ◽  
Piv Analysis

The effect of ethanol in the binary solution sessile droplet is investigated on the flow field, nanoparticle motion and nanoparticle deposition pattern. It is found that the droplets with ethanol exhibited three distinct flow regimes through the Particle Image Velocimetry (PIV) analysis on the flow field of droplets suspended with fluorescent microspheres. Regime I features furious flows and vortices which transport particles to the liquid-vapor interface and make them aggregate. In regime II, the aggregates of particles move towards the central area of the droplet dominated by Marangoni flow led by non-uniformity of ethanol along the droplet surface. As the droplet enters regime III, most ethanol has evaporated and it is dominated by the drying of the remaining water. The loading of ethanol in the solution prolongs the relative durations of regimes I and II, resulting in the variety of the final drying pattern of nanoparticles.

On the Origin of the Bump in the Profile of Surface-Tension-Gradient-Driven Spreading Films

1991 ◽  
Vol 248 ◽  
Author(s):  
P. Carles ◽  
A.M. Cazabat
Keyword(s):  
Surface Tension ◽  
Steady State ◽  
Contact Line ◽  
Surface Tension Gradient ◽  
Simple Analysis

AbstractWe show that the presence of a bump, in the profile of spreading films driven by forces such as surface tension gradients, can be explained by a simple analysis of the steady-state velocity, without taking into account contact line effects.

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