Condensation Droplet Distribution Regulated by Electrowetting

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
Run Yan ◽  
Chung-Lung Chen
Keyword(s):  
Transfer Rate ◽  
Droplet Growth ◽  
Electrode Design ◽  
Electrowetting On Dielectric ◽  
Charged Surfaces ◽  
Droplet Distribution ◽  
Novel Approach ◽  
Single Side ◽  
Shedding Frequency ◽  
Thick Wire

Abstract This paper presents a visualization of condensation droplet distribution affected by the electrowetting-on-dielectric (EWOD) approach. A single-side double-layer-electrode design (grid wire, thin wire, and thick wire) and coplanar-electrode design (zigzag) are discussed. Side-by-side experiments with applied 40 V DC electric potential are carried out to compare droplet distribution between identically designed charged and uncharged devices. The uncharged devices show a random droplet distribution, whereas charged devices have a regulated distribution based on the designed patterns. As droplets on the electrode boundaries become larger, they are likely to slide away and stay in electrode-free regions. The droplets “sit” inside the grid wires and distribute vertically along thin and thick wires. On the coplanar-electrode zigzag device, droplets are distributed vertically. The charged surfaces lead to a faster droplet growth rate and more dispersed droplet distribution. This phenomenon accelerates the shedding frequency of the droplets and frees up more areas for small droplets to nucleate and grow. The first shedding moment of the charged surfaces occurs earlier than the uncharged ones for all types of EWOD devices. The detected droplet shedding diameter ranges from 1.2 mm to 2.5 mm in this study. The number of large droplets is found greater on the charged devices compared with the uncharged devices and theoretical model. The work presented in this paper introduces a novel approach to actively influence droplet distribution on microfabricated condensing surfaces and indicates great potential for improving the condensation heat transfer rate via EWOD.

Condensation Droplet Distribution Affected by Electrowetting Approach

2019 ◽  
Author(s):  
Run Yan ◽  
Chung-Lung (C. L.) Chen
Keyword(s):  
Transfer Rate ◽  
Droplet Growth ◽  
Electrode Design ◽  
Electrowetting On Dielectric ◽  
Charged Surfaces ◽  
Droplet Distribution ◽  
Novel Approach ◽  
Single Side ◽  
Shedding Frequency ◽  
Thick Wire

Abstract This paper presents a visualization of condensation droplet distribution affected by the electrowetting-on-dielectric (EWOD) approach. A single-side double-layer-electrode design (grid wire, thin wire, and thick wire) and coplanar-electrode design (zigzag) are discussed. Side-by-side experiments with applied 40V DC electric potential are carried out to compare droplet distribution between charged and uncharged devices with the identical design. The uncharged devices show a random droplet distribution, whereas charged devices have a regulated distribution based on the designed patterns. As droplets on the electrode boundaries become larger, they are likely to slide away and stay in electrode-free regions. The droplets ‘sit’ inside the grid wires and distribute vertically along thin and thick wires. On the coplanar-electrode zigzag device, droplets cover the electrode gaps and are distributed vertically. The charged surfaces lead to a faster droplet growth rate, resulting in larger droplet size and more dispersed droplet distribution. This phenomenon accelerates droplets’ shedding frequency and frees up more condensing areas for small droplets to nucleate and grow. The first shedding moment of the charged surfaces occurs earlier than the uncharged ones for all types of EWOD devices. The detected droplet shedding diameter ranges from 1.2 mm to 2 mm in this study. The work presented in this paper introduces a novel approach to actively influence droplet distribution on microfabricated condensing surfaces and indicates great potential for improving condensation heat transfer rate via EWOD.

scholarly journals Water harvesting and condensation heat transfer enhancement induced with electrowetting-on-dielectric

2019 ◽  
Author(s):  
◽  
Run Yan
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Heat Transfer Enhancement ◽  
Condensation Heat Transfer ◽  
Water Harvesting ◽  
Transfer Enhancement ◽  
Electrowetting On Dielectric ◽  
Droplet Distribution ◽  
Condensation Heat Transfer Enhancement

As demand for the world's natural resources continues to rise, energy saving has become an urgent topic. Water harvesting and condensation heat transfer enhancement represent two vital energy-saving objectives. Many researchers have focused on alternating surface wettability by employing advanced materials or complex surface structures to achieve such goals; however, most of these approaches operate in a passive manner. In terms of active methods, electrowetting-on-dielectric (EWOD) has become a popular option owing to its excellent contact angle reversibility, switching speed, and long-term reliability in altering surface wettability. This dissertation presents a study of the EWOD effect on water harvesting and condensation heat transfer. It describes experimental and analytical studies concerning various characteristics such as EWOD-induced droplet dynamics, water capture capability, and heat transfer performance. It also quantifies water harvesting and condensation heat transfer enhancement. This dissertation is divided into four main studies, each of which considers different aspects of the effects of EWOD on water harvesting and condensation heat transfer. The first part of this dissertation (Chapter 2) describes microfabrication technologies to obtain EWOD devices, including low-pressure chemical vapor deposition, photolithography, sputtering deposition, and lift-off and spin coating. Mask designs with different electrode configurations and a device microfabrication protocol are also described. The second part of this dissertation (Chapter 3) presents an experimental investigation of EWOD-induced water harvesting enhancement. EWOD devices were tested in a high-humidity environment under mist flow. Compared with an uncharged EWOD device, the water capture capability of charged devices improved significantly. These results are of great importance, as they indicate strong potential for improvement in water-harvesting applications. The third part of this dissertation (Chapter 4) describes a visualization study of EWOD-regulated condensation droplet distribution. Side-by-side experiments were performed to compare charged and uncharged devices. Charged devices exhibited a regulated droplet distribution, faster droplet growth, more dispersed droplet distribution, and more large droplets. These experimental results introduced a novel approach to actively influence droplet distribution on microfabricated condensing surfaces and showed promise for improving the condensation heat transfer rate via EWOD. The fourth part of this dissertation (Chapter 5) discusses the EWOD effect on the condensation heat transfer coefficient and heat flux. The heat transfer coefficient and heat flux were compared on uncharged and charged (40V DC) EWOD devices. Experimental results demonstrated a positive effect of EWOD on condensation heat transfer. This approach could be incorporated into many industrial applications (e.g., heat exchanger fin surfaces, condensing surfaces of waste heat recovery systems, and components of electronic cooling packages) requiring high-efficiency heat dissipation. In summary, this work makes valuable contributions to the field of water harvesting and condensation heat transfer, proposing a new approach to research in these areas. Findings also detail a new tool to achieve water harvesting and condensation heat transfer enhancement via an active EWOD method.

scholarly journals Optocontrol of glutamate receptor activity by single side-chain photoisomerization

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Viktoria Klippenstein ◽  
Christian Hoppmann ◽  
Shixin Ye ◽  
Lei Wang ◽  
Pierre Paoletti
Keyword(s):  
Protein Function ◽  
Light Sensitivity ◽  
Site Directed Mutagenesis ◽  
Single Amino Acid ◽  
General Applicability ◽  
Neuronal Protein ◽  
Novel Approach ◽  
Single Side ◽  
Dynamic Dimension ◽  
Pore Domain

Engineering light-sensitivity into proteins has wide ranging applications in molecular studies and neuroscience. Commonly used tethered photoswitchable ligands, however, require solvent-accessible protein labeling, face structural constrains, and are bulky. Here, we designed a set of optocontrollable NMDA receptors by directly incorporating single photoswitchable amino acids (PSAAs) providing genetic encodability, reversibility, and site tolerance. We identified several positions within the multi-domain receptor endowing robust photomodulation. PSAA photoisomerization at the GluN1 clamshell hinge is sufficient to control glycine sensitivity and activation efficacy. Strikingly, in the pore domain, flipping of a M3 residue within a conserved transmembrane cavity impacts both gating and permeation properties. Our study demonstrates the first detection of molecular rearrangements in real-time due to the reversible light-switching of single amino acid side-chains, adding a dynamic dimension to protein site-directed mutagenesis. This novel approach to interrogate neuronal protein function has general applicability in the fast expanding field of optopharmacology.

A Novel Approach of Designing Aircraft Heat Exchanger for Continuous Working Conditions Using Modified Genetic Algorithm

2019 ◽  
Author(s):  
Qihang Liu ◽  
Laihe Zhuang ◽  
Yanchen Fu ◽  
Bensi Dong ◽  
Jie Wen ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Heat Transfer Rate ◽  
Working Conditions ◽  
Transfer Rate ◽  
Optimization Design ◽  
Working Condition ◽  
Structural Parameters ◽  
Novel Approach

Abstract A novel approach is proposed to design an aircraft heat exchanger considering multiple working conditions to develop the conventional approach that designs for only one working condition. Calculation results show that the performance of the heat exchangers designed by this novel approach meets the requirement of pressure drop and heat transfer for all working conditions (flight height varies from 0 m to 12,000 m, and Mach number varies from 0 to 1.2). After working conditions discrete and heat exchanger design, the extreme working conditions of pressure drop and heat transfer rate are found not coincided, which have been all considered in design without artificially screening. Therefore, it is not necessary to find a ‘seeming extreme working condition’ before design for this approach. In the optimization design, a deeply optimized structure of heat exchanger is proposed by changing the values of the selected structural parameters to reduce by roughly 30% of the total weight in comparison to common design results. Moreover, the pressure drop and the heat transfer rate of the optimal result can be reasonably distributed at different working conditions. Actually in this novel approach, more other specific criteria required could be also added into the integrate criterion of optimization to control the result. In addition, two detailed optimization methods, sacrifice of secondary objective parameters and ‘the macro-to-micro design method’, have been proposed in optimization design for further optimal structure.

scholarly journals AN ANALYSIS OF THE LIQUID FILMS BREAK-UP USING THE COMPUTER VISION TECHNIQUE

2021 ◽  
Vol 61 (1) ◽  
pp. 253-269
Author(s):  
Lucie Měšťanová ◽  
Ondřej Bartoš
Keyword(s):  
Image Processing ◽  
Wind Tunnel ◽  
High Speed ◽  
Optical Measurement ◽  
Liquid Films ◽  
Light Extinction ◽  
Steam Turbines ◽  
Droplet Distribution ◽  
Novel Approach ◽  
Unfavourable Effect

The aim of this paper is to introduce a novel approach for analysing the droplet formation in a transonic flow. The method suggested in this work is based on the combination of the measured data from the wind tunnel by an optical measurement and image processing. A new wind tunnel was developed for the study of the liquid film atomization at high speed flows similar to ones that can be found in steam turbines. The coarse droplets in steam turbines are formed from the liquid films on the blades and inner casings. The coarse droplets formed on the stator blades don´t follow the bulk flow and collide with the following moving blades. These collisions cause erosion and corrosion processes, which have an unfavourable effect on the reliability and the efficiency of the low pressure stages of steam turbines. The tunnel is equipped with a standard instrumentation for the measurement of the flow properties and for the analysis of the size distribution of the droplets. Two measurement methods were used for the measurement of the size of the droplets, photogrammetry and light scattering. In this paper, the image processing of the captured images is discussed. The images were taken by a camera with a telecentric lens. The paper contains an assessment of three image processing methods used for the measurement of the droplet distribution by the light extinction. Moreover, the formation of the droplets is captured on the trailing edge of the profile in the flow. The results bring a new view on the formation of droplets at high speeds.

Measuring the electrical and optical properties of fog using balloon borne instrumentation in the UAE

2020 ◽  
Author(s):  
Graeme Marlton ◽  
Giles Harrison ◽  
Keri Nicoll ◽  
Maarten Ambaum
Keyword(s):  
Optical Properties ◽  
Charge Density ◽  
United Arab Emirates ◽  
Electric Charge ◽  
Optical Sensors ◽  
Growth Models ◽  
Abu Dhabi ◽  
Droplet Growth ◽  
Electrical And Optical Properties ◽  
Droplet Distribution

<p>Countries in arid and desert climates that have small amounts of rainfall each year use cloud seeding techniques to enhance the little rainfall that is present. Typically, this is achieved by seeding the cloud with hygroscopic nuclei to increase the rainfall. A possible alternative method is to inject the cloud with electric charge, which has been shown in models to alter the droplet size and distribution and influence rainfall properties.</p><p>Here, in-situ observations of the electrical and optical properties of clouds are described from a desert site. These are used to inform droplet growth models. For this, a yearlong campaign, during which 10 weather balloons carrying electric charge and optical sensors were launched through fog layers from Abu Dhabi airport, United Arab Emirates. Here we present 2 case studies. The first is a clear air ascent comparison between the desert site at Abu Dhabi and a temperate site in northern Finland. The second is a fog comparison between Abu Dhabi and a temperate site in the United Kingdom</p><p>The results show that the fogs in Abu Dhabi are highly charged with a charge density of 0.1-1 nC m<sup>-3</sup> as opposed to the charge densities of fogs in Northern Hemisphere temperate regions which have a typical charge density of 10 pC m<sup>-3</sup>. The droplet concentration in the Abu Dhabi fog case study is significantly smaller, approximately 150 cm<sup>-3</sup> as opposed to droplet concentrations of 300-400 cm<sup>-3</sup> in fog over a temperate site.</p><p>The results suggest that dust contributes strongly to the atmospheric electrical conditions in the UAE region, due to charging of the dust tribo-electrically. This dust charge may also affect the droplet distribution within the fog. These new measurements of the vertical profile of charge through fog layers in desert climates will be used to improve understanding in droplet growth models.</p>

scholarly journals A novel double-side welding approach for friction stir welding of polypropylene plate

2021 ◽  
Author(s):  
Rahul Kanti Nath ◽  
Vinayak Jha ◽  
Pabitra Maji ◽  
John Deb Barma
Keyword(s):  
Friction Stir Welding ◽  
Material Flow ◽  
Polymer Materials ◽  
High Demand ◽  
Cross Sectional ◽  
Friction Stir ◽  
Novel Approach ◽  
Single Side ◽  
Cost Efficient ◽  
Welding Technique

AbstractIn almost every industry, polymer materials are in high demand in recent years due to their lightweight and easy formability. However, eco-friendly, cost-efficient and defect-free joining of polymers is a major concern. In this article, a novel approach is taken for friction stir welding of polypropylene by implementing a double-side welding technique. The effect of tool rotational speed on construction and properties of the welded joints are studied. The torque and forces exerted on the tool during double-side welding are compared with single-side welding. Cross-sectional morphology examination using optical and scanning electron microscope reveals defect-free sound welding by double-side weld with uniform material flow. The molecular bonds of the welded specimens are examined by FTIR analysis. The double-side welding technique yields superior joints in terms of tensile strength and flexural strength than the joints obtained by single-side welding.

Copper-dependent ATP7B up-regulation drives the resistance of TMEM16A-overexpressing head-and-neck cancer models to platinum toxicity

2019 ◽  
Vol 476 (24) ◽  
pp. 3705-3719 ◽  
Author(s):  
Avani Vyas ◽  
Umamaheswar Duvvuri ◽  
Kirill Kiselyov
Keyword(s):  
Oxidative Stress ◽  
Head And Neck ◽  
Transcriptional Activation ◽  
Platinum Resistance ◽  
Mrna Levels ◽  
Strong Positive Correlation ◽  
Platinum Compounds ◽  
Copper Chelation ◽  
Novel Approach ◽  
Cancer Models

Platinum-containing drugs such as cisplatin and carboplatin are routinely used for the treatment of many solid tumors including squamous cell carcinoma of the head and neck (SCCHN). However, SCCHN resistance to platinum compounds is well documented. The resistance to platinum has been linked to the activity of divalent transporter ATP7B, which pumps platinum from the cytoplasm into lysosomes, decreasing its concentration in the cytoplasm. Several cancer models show increased expression of ATP7B; however, the reason for such an increase is not known. Here we show a strong positive correlation between mRNA levels of TMEM16A and ATP7B in human SCCHN tumors. TMEM16A overexpression and depletion in SCCHN cell lines caused parallel changes in the ATP7B mRNA levels. The ATP7B increase in TMEM16A-overexpressing cells was reversed by suppression of NADPH oxidase 2 (NOX2), by the antioxidant N-Acetyl-Cysteine (NAC) and by copper chelation using cuprizone and bathocuproine sulphonate (BCS). Pretreatment with either chelator significantly increased cisplatin's sensitivity, particularly in the context of TMEM16A overexpression. We propose that increased oxidative stress in TMEM16A-overexpressing cells liberates the chelated copper in the cytoplasm, leading to the transcriptional activation of ATP7B expression. This, in turn, decreases the efficacy of platinum compounds by promoting their vesicular sequestration. We think that such a new explanation of the mechanism of SCCHN tumors’ platinum resistance identifies novel approach to treating these tumors.

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