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.

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.

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.

scholarly journals Evaluating Energy and Cost Requirements for Different Configurations of Off-Grid Rainwater Harvesting Systems

Water ◽  
2018 ◽  
Vol 10 (8) ◽  
pp. 1024
Author(s):  
Heather Rose ◽  
Charles Upshaw ◽  
Michael Webber
Keyword(s):  
Rainwater Harvesting ◽  
Uv Light ◽  
Storage System ◽  
Energy Storage System ◽  
System Model ◽  
Demand System ◽  
Solar Pv ◽  
On Demand ◽  
Harvesting Systems ◽  
System Configurations

The goal of this analysis was to evaluate energy and cost requirements for different configurations of a rainwater harvesting (RWH) system in conjunction with a solar PV and energy storage system for an off-grid house. Using models in fluid mechanics, we evaluated energy and power requirements for four different system configurations: 1. An On-Demand System containing a single speed pump (OD-SS), 2. An On-Demand System containing a variable speed pump (OD-VS), 3. A Pressurized Storage System where water is pumped once during the day into a large pressurized tank for later consumption and treated on demand via UV light (PS-AOT), and 4. A Pressurized Storage System where water is treated once per day via UV light and then stored for later consumption (PS-TO). Our analysis showed that the OD-SS system model requires 2.63 kWh per day, the OD-VS system model requires a total energy of 1.65 kWh per day, and the PS-AOT requires 1.67–1.69 kWh per day depending on the pump size, and the PS-TO system requires 0.19–0.36 kWh per day depending on the pump size. When comparing estimated cost between systems, we found the OD-SS system to be the most expensive. With the OD-SS system as a base for system costs, we found the OD-VS system to be 39% less expensive, the PS-AOT system to be 21% less expensive, and the PS-TO system to be 60% less expensive than the base OD-SS system.

Optical Adhesion Control of Hydrogel Microtools for On-Demand Immobilization and Measurement of Cells on a Microfluidic Chip

2010 ◽  
Vol 22 (5) ◽  
pp. 631-638 ◽  
Author(s):  
Hisataka Maruyama ◽  
◽  
Toshio Fukuda ◽  
Fumihito Arai ◽  
Keyword(s):  
Optical Tweezers ◽  
Microfluidic Chip ◽  
Electrolyte Concentration ◽  
Ph Value ◽  
Uv Light ◽  
Yeast Cells ◽  
Light Illumination ◽  
Local Conditions ◽  
On Demand ◽  
Adhesion Control

Optical adhesion control of hydrogel microtools, made of hydrophilic photo-crosslinkable resin, was developed for on-demand immobilization and measurement of cells on a microfluidic chip. The hydrogel microtool was manipulated by optical tweezers and modified by spiropyran chromospheres, which was a photochromic polymer. We developed on-demand control of uni/bidirectional adhesiveness of the microtool by control of electrolyte concentration in a solution. Photo illumination controls the adhesiveness of the microtools. In case of unidirectional control of adhesiveness, the microtools adhere to glass, other microtools and cells by illumination of ultraviolet (UV) light. Spiropyran chromospheres were used for bidirectional control of adhesiveness to cell. In case of bidirectional control of adhesiveness, the microtools adhere to cells by UV illumination. On the other hand, the microtool detaches from the adhered cells by visible (VIS) light illumination. Electrolyte concentration in the solution controlled these adhesiveness controls. Adherence of the microtool was enough to keep its position on a microfluidic chip. We applied these immobilization methods to measure the local conditions around cells by modifying the microtool with a pH indicator, bromothymol blue (BTB). Local measurements of the ambient pH value of yeast cells were performed by immobilizing the cell on the surface of the pH sensing microtool. Moreover, culture monitoring of a single yeast cell was demonstrated by immobilization to the microtool.

scholarly journals Engineered Th17 cell differentiation using a photo-activatable immune modulator

2019 ◽  
Author(s):  
Bibudha Parasar ◽  
Pamela V. Chang
Keyword(s):  
Cell Differentiation ◽  
Th17 Cell ◽  
Th17 Cells ◽  
Uv Light ◽  
T Cell Subsets ◽  
Light Illumination ◽  
Immune Modulator ◽  
On Demand ◽  
Th17 Cell Differentiation

AbstractT helper 17 (Th17) cells, an important subset of CD4+ T cells, help to eliminate extracellular infectious pathogens that have invaded our tissues. Despite the critical roles of Th17 cells in immunity, how the immune system regulates the production and maintenance of this cell type remains poorly understood. In particular, the plasticity of these cells, or their dynamic ability to trans-differentiate into other CD4+ T cell subsets, remains mostly uncharacterized. Here, we report a synthetic immunology approach using a photo-activatable immune modulator (PIM) to increase Th17 cell differentiation on demand with spatial and temporal precision to help elucidate this important and dynamic process. In this chemical strategy, we developed a latent agonist that, upon photochemical activation, releases a small-molecule ligand that targets the aryl hydrocarbon receptor (AhR) and ultimately induces Th17 cell differentiation. We used this chemical tool to control AhR activation with spatiotemporal precision within cells and to modulate Th17 cell differentiation on demand by using UV light illumination. We envision that this approach will enable an understanding of the dynamic functions and behaviors of Th17 cells in vivo during immune responses and in mouse models of inflammatory disease.

Particle Transport in Quasistatic Stokes Flow

1999 ◽  
Author(s):  
Russell Keanini
Keyword(s):  
Traveling Waves ◽  
Stokes Flow ◽  
Particle Transport ◽  
Small Amplitude ◽  
Large Scale ◽  
Second Order ◽  
Particle Agglomeration ◽  
Long Time ◽  
Short Time ◽  
Streaming Flow

Abstract Particle transport associated with quasistatic second-order streaming flow in wavy-walled channels is theoretically investigated. Small amplitude tangential oscillations of both walls drive steady second-order streaming, while superposed, large-amplitude oscillations of one wall produce the time-dependent, quasisteady flows of interest. Short-time transport is characterized by collective particle motion in the direction of large-scale boundary displacement and by filamentary motion in the opposite direction, both consistent with transport in traveling waves [E. Moses and V. Steinburg, Phys. Rev. Lett. 60, 2030 (1988)]. Long time or asymptotic transport is characterized by particle agglomeration toward, or repulsion from, moving elliptic points. Under certain conditions, collective, periodic motion on the periphery of central cells also occurs. These characteristics correspond respectively to attraction or repulsion to or from period-1 elliptic points and attraction toward limit cycles on the Poincare map.

scholarly journals On the Use of Pulsed UV or Visible Light Activated Gas Sensing of Reducing and Oxidising Species with WO3 and WS2 Nanomaterials

Sensors ◽  
2021 ◽  
Vol 21 (11) ◽  
pp. 3736
Author(s):  
Ernesto González ◽  
Juan Casanova-Chafer ◽  
Aanchal Alagh ◽  
Alfonso Romero ◽  
Xavier Vilanova ◽  
...  
Keyword(s):  
Visible Light ◽  
Prediction Models ◽  
Gas Sensing ◽  
Uv Light ◽  
Model Performance ◽  
Principal Component Regression ◽  
Principal Component ◽  
Light Modulation ◽  
Gas Concentration ◽  
P Type

This paper presents a methodology to quantify oxidizing and reducing gases using n-type and p-type chemiresistive sensors, respectively. Low temperature sensor heating with pulsed UV or visible light modulation is used together with the application of the fast Fourier transform (FFT) to extract sensor response features. These features are further processed via principal component analysis (PCA) and principal component regression (PCR) for achieving gas discrimination and building concentration prediction models with R2 values up to 98% and RMSE values as low as 5% for the total gas concentration range studied. UV and visible light were used to study the influence of the light wavelength in the prediction model performance. We demonstrate that n-type and p-type sensors need to be used together for achieving good quantification of oxidizing and reducing species, respectively, since the semiconductor type defines the prediction model's effectiveness towards an oxidizing or reducing gas. The presented method reduces considerably the total time needed to quantify the gas concentration compared with the results obtained in a previous work. The use of visible light LEDs for performing pulsed light modulation enhances system performance and considerably reduces cost in comparison to previously reported UV light-based approaches.

Evaporative Deposition of Bacteria and Microspheres on Mica from a Sessile Drop: The Use of Surface Conditioning in a Laboratory Atmosphere to Control Drop Spreading and Particle Deposition Patterns

2010 ◽  
Vol 1273 ◽  
Author(s):  
Joan E Curry ◽  
Raina M. Maier ◽  
Theresa A. Norris ◽  
Kyle Fisher Baughman
Keyword(s):  
Contact Angle ◽  
Particle Deposition ◽  
Colloidal Particles ◽  
Colloidal Particle ◽  
Sessile Drop ◽  
Mica Surface ◽  
Deposition Pattern ◽  
Deposition Patterns ◽  
Drop Spreading ◽  
Surface Conditioning

AbstractEvaporative deposition from a sessile drop is an appealing way to deposit materials on a surface due to the simplicity of the technique. In this work we deposit aqueous solutions of two types of colloidal particles, namely bacteria and microspheres, on mica. We show that by controlling the extent of initial drop spreading through subtle changes in surface conditioning caused by exposure to the laboratory atmosphere in a laminar flow hood it is possible to systematically vary the particle deposition patterns. On freshly cleaved mica the contact angle of water is < 5°. Drops of bacterial and microsphere solutions deposited on freshly cleaved mica spread to cover a large surface area. Drying occurs through pinning and depinning events leaving a series of colloidal particle rings. We found in our laboratory that the contact angle of water on mica exposed to a constant flow of filtered laboratory air in a laminar flow hood gradually increases with time. For drops of both bacterial and microsphere solutions there is a corresponding decrease in the extent of drop spreading with increasing exposure of the mica surface to laboratory air. This results in a profound change in the colloidal particle deposition pattern. Short exposures of minutes to hours are enough to decrease spreading and affect the resulting deposition pattern. For our longest mica surface exposure times (months to 1 year) the contact angle of water reaches values near 20°. Spreading of the bacterial and microsphere drops is substantially decreased. A portion of the colloidal particles are deposited in an outer deposition ring which marks the extent of drop spreading and the remainder of the particles are deposited in the drop interior as a honeycomb or cellular film. The fraction of the drop residue covered with the cellular film increases with particle concentration as well as the length of time the mica is exposed to the laboratory atmosphere. This work shows that evaporative deposition on mica is very sensitive to surface conditioning through atmospheric exposure and also suggests that particle deposition patterns can be tuned by small changes in drop spreading.

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