scholarly journals Hierarchical Superhydrophobic Copper for Sustained Dropwise Condensation

2015 ◽  
Vol 137 (8) ◽  
Author(s):  
Xuemei Chen ◽  
Justin A. Weibel
Keyword(s):  
Growth Dynamics ◽  
Time Lapse ◽  
Droplet Surface ◽  
Droplet Growth ◽  
Environmental Scanning ◽  
Dropwise Condensation ◽  
Droplet Motion ◽  
Surface Design ◽  
Industrial Systems ◽  
The Hill

Engineering surfaces that sustain continuous dropwise condensation, and are composed of materials commonly employed in heat transfer applications, are of great interest for scaled-up industrial systems. We fabricate hierarchical micro/nano-structured superhydrophobic surfaces on copper substrates. Condensate droplet growth dynamics on the as-fabricated samples were investigated using an environmental scanning electron microscope (ESEM; FEI Quanta 3D, ~6 torr, ~3 °C stage). Time-lapse ESEM images show that the condensate droplets preferentially nucleate at the bases of the hill-shaped microstructures (40 s). The droplets at the microstructure bases coalesce; merged droplets rise and appear to be suspended atop adjacent microstructures (180-220 s). These droplets, when triggered by coalescence, can gain sufficient kinetic energy by a reduction in droplet surface area/energy to spontaneously depart from the substrate. This droplet motion sweeps additional droplets in the trajectory and exposes fresh space for formation of new droplets (220-250 s). These droplet growth and departure dynamics are facilitated by the combination of microscale and nanoscale roughness features on the surface, and the behavior provides important insight into surface design requirements for sustaining dropwise condensation in thermal management applications.

Electrowetting-Based Coalescence of Droplets During Dropwise Condensation of Humid Air

2019 ◽  
Author(s):  
Enakshi Wikramanayake ◽  
Vaibhav Bahadur
Keyword(s):  
Heat Transfer ◽  
Electric Field ◽  
Electric Fields ◽  
Applied Electric Field ◽  
Growth Dynamics ◽  
Condensation Heat Transfer ◽  
Droplet Growth ◽  
Dropwise Condensation ◽  
Condensation Rate ◽  
Humid Air

Abstract Dropwise condensation yields higher heat transfer coefficients by avoiding the thermal resistance of the condensate film, seen during filmwise condensation. This work explores further enhancement of dropwise condensation heat transfer through the use of electrowetting to achieve faster droplet growth via coalescence of the condensed droplets. Electrowetting is a well understood microfluidic technique to actuate and control droplets. This work shows that AC electric fields can significantly enhance droplet growth dynamics. This enhancement is a result of coalescence triggered by various types of droplet motion (translation of droplets, oscillations of three phase line), which in turn depends on the frequency of the applied AC waveform. The applied electric field modifies droplet condensation patterns as well as the roll-off dynamics on the surface. Experiments are conducted to study early-stage droplet growth dynamics, as well as steady state condensation rates under the influence of electric fields. It is noted that this study deals with condensation of humid air, and not pure steam. Results show that increasing the voltage magnitude and frequency increases droplet growth rate and overall condensation rate. Overall, this study reports more than a 30 % enhancement in condensation rate resulting from the applied electric field, which highlights the potential of this concept for condensation heat transfer enhancement.

SINGLE DROPLET GROWTH MODEL FOR DROPWISE CONDENSATION CONSIDERING NON-CONDENSABLE GAS

2018 ◽  
Author(s):  
Shaofei Zheng ◽  
Ferdinand Eimann ◽  
Christian Philipp ◽  
Ulrich Gross
Keyword(s):  
Growth Model ◽  
Droplet Growth ◽  
Dropwise Condensation ◽  
Single Droplet

scholarly journals Development of single-cell-level microfluidic technology for long-term growth visualization of living cultures of Mycobacterium smegmatis

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Han Wang ◽  
Gloria M. Conover ◽  
Song-I Han ◽  
James C. Sacchettini ◽  
Arum Han
Keyword(s):  
Drug Treatment ◽  
Single Cell ◽  
Mycobacterium Smegmatis ◽  
Culture Media ◽  
Low Cost ◽  
Bacterial Pathogen ◽  
Growth Dynamics ◽  
Time Lapse ◽  
Cell Phenotype

AbstractAnalysis of growth and death kinetics at single-cell resolution is a key step in understanding the complexity of the nonreplicating growth phenotype of the bacterial pathogen Mycobacterium tuberculosis. Here, we developed a single-cell-resolution microfluidic mycobacterial culture device that allows time-lapse microscopy-based long-term phenotypic visualization of the live replication dynamics of mycobacteria. This technology was successfully applied to monitor the real-time growth dynamics of the fast-growing model strain Mycobacterium smegmatis (M. smegmatis) while subjected to drug treatment regimens during continuous culture for 48 h inside the microfluidic device. A clear morphological change leading to significant swelling at the poles of the bacterial membrane was observed during drug treatment. In addition, a small subpopulation of cells surviving treatment by frontline antibiotics was observed to recover and achieve robust replicative growth once regular culture media was provided, suggesting the possibility of identifying and isolating nonreplicative mycobacteria. This device is a simple, easy-to-use, and low-cost solution for studying the single-cell phenotype and growth dynamics of mycobacteria, especially during drug treatment.

scholarly journals Stochasticity in Colonial Growth Dynamics of Individual Bacterial Cells

2013 ◽  
Vol 79 (7) ◽  
pp. 2294-2301 ◽  
Author(s):  
Konstantinos P. Koutsoumanis ◽  
Alexandra Lianou
Keyword(s):  
Kinetic Parameters ◽  
Single Cells ◽  
Growth Curves ◽  
Growth Dynamics ◽  
Time Lapse ◽  
Initial Population ◽  
Bacterial Cells ◽  
Stochastic Growth ◽  
Bacterial Populations ◽  
Content Type

ABSTRACTConventional bacterial growth studies rely on large bacterial populations without considering the individual cells. Individual cells, however, can exhibit marked behavioral heterogeneity. Here, we present experimental observations on the colonial growth of 220 individual cells ofSalmonella entericaserotype Typhimurium using time-lapse microscopy videos. We found a highly heterogeneous behavior. Some cells did not grow, showing filamentation or lysis before division. Cells that were able to grow and form microcolonies showed highly diverse growth dynamics. The quality of the videos allowed for counting the cells over time and estimating the kinetic parameters lag time (λ) and maximum specific growth rate (μmax) for each microcolony originating from a single cell. To interpret the observations, the variability of the kinetic parameters was characterized using appropriate probability distributions and introduced to a stochastic model that allows for taking into account heterogeneity using Monte Carlo simulation. The model provides stochastic growth curves demonstrating that growth of single cells or small microbial populations is a pool of events each one of which has its own probability to occur. Simulations of the model illustrated how the apparent variability in population growth gradually decreases with increasing initial population size (N0). For bacterial populations withN0of >100 cells, the variability is almost eliminated and the system seems to behave deterministically, even though the underlying law is stochastic. We also used the model to demonstrate the effect of the presence and extent of a nongrowing population fraction on the stochastic growth of bacterial populations.

A Heat Transfer Model of Dropwise Condensation Underneath a Horizontal Substrate

2011 ◽  
Vol 199-200 ◽  
pp. 1604-1608
Author(s):  
Yun Fu Chen
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Contact Angle ◽  
Fractal Model ◽  
Condensation Heat Transfer ◽  
Droplet Growth ◽  
Transfer Model ◽  
Dropwise Condensation ◽  
Small Contact Angle ◽  
Horizontal Substrate

For finding influence of the condensing surface to dropwise condensation heat transfer, a fractal model for dropwise condensation heat transfer has been established based on the self-similarity characteristics of droplet growth at various magnifications on condensing surfaces with considering influence of contact angle to heat transfer. It has been shown based on the proposed fractal model that the area fraction of drops decreases with contact angle increase under the same sub-cooled temperature; Varying the contact angle changes the drop distribution; higher the contact angle, lower the departing droplet size and large number density of small droplets; dropwise condensation translates easily to the filmwise condensation at the small contact angle ;the heat flux increases with the sub-cooled temperature increases, and the greater of contact angle, the more heat flux increases slowly.

scholarly journals Cell-to-cell heterogeneity in Escherichia coli stress response originates from pulsatile expression and growth

2020 ◽  
Author(s):  
Nadia M. V. Sampaio ◽  
Caroline M. Blassick ◽  
Jean-Baptiste Lugagne ◽  
Mary J. Dunlop
Keyword(s):  
Gene Expression ◽  
Escherichia Coli ◽  
Stress Response ◽  
Single Cell ◽  
Phenotypic Variability ◽  
Growth Dynamics ◽  
Time Lapse ◽  
Cell Heterogeneity ◽  
Temporal Expression ◽  
Functional Consequences

AbstractCell-to-cell heterogeneity in gene expression and growth can have critical functional consequences, such as determining whether individual bacteria survive or die following stress. Although phenotypic variability is well documented, the dynamics that underlie it are often unknown. This information is critical because dramatically different outcomes can arise from gradual versus rapid changes in expression and growth. Using single-cell time-lapse microscopy, we measured the temporal expression of a suite of stress response reporters in Escherichia coli, while simultaneously monitoring growth rate. In conditions without stress, we found widespread examples of pulsatile expression. Single-cell growth rates were often anti-correlated with gene expression, with changes in growth preceding changes in expression. These pulsatile dynamics have functional consequences, which we demonstrate by measuring survival after challenging cells with the antibiotic ciprofloxacin. Our results suggest that pulsatile expression and growth dynamics are common in stress response networks and can have direct consequences for survival.

Droplet Growth Dynamics during Atmospheric Condensation on Nanopillar Surfaces

2018 ◽  
Vol 22 (4) ◽  
pp. 270-295 ◽  
Author(s):  
Mohammad Rejaul Haque ◽  
Chuang Qu ◽  
Edward C. Kinzel ◽  
Amy Rachel Betz
Keyword(s):  
Growth Dynamics ◽  
Droplet Growth

scholarly journals Efficient microbial colony growth dynamics quantification with ColTapp, an automated image analysis application

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Julian Bär ◽  
Mathilde Boumasmoud ◽  
Roger D. Kouyos ◽  
Annelies S. Zinkernagel ◽  
Clément Vulin
Keyword(s):  
Growth Dynamics ◽  
Time Lapse ◽  
Colony Growth ◽  
Lag Time ◽  
Automated Image Analysis ◽  
Clinical Samples ◽  
Clinical Settings ◽  
Bacterial Colony ◽  
Analysis Application ◽  
Population Survival

Abstract Populations of genetically identical bacteria are phenotypically heterogeneous, giving rise to population functionalities that would not be possible in homogeneous populations. For instance, a proportion of non-dividing bacteria could persist through antibiotic challenges and secure population survival. This heterogeneity can be studied in complex environmental or clinical samples by spreading the bacteria on agar plates and monitoring time to growth resumption in order to infer their metabolic state distribution. We present ColTapp, the Colony Time-lapse application for bacterial colony growth quantification. Its intuitive graphical user interface allows users to analyze time-lapse images of agar plates to monitor size, color and morphology of colonies. Additionally, images at isolated timepoints can be used to estimate lag time. Using ColTapp, we analyze a dataset of Staphylococcus aureus time-lapse images including populations with heterogeneous lag time. Colonies on dense plates reach saturation early, leading to overestimation of lag time from isolated images. We show that this bias can be corrected by taking into account the area available to each colony on the plate. We envision that in clinical settings, improved analysis of colony growth dynamics may help treatment decisions oriented towards personalized antibiotic therapies.

Filmwise-to-Dropwise Condensation Transition Enabled by Patterned High Wetting Contrast

2015 ◽  
Vol 137 (8) ◽  
Author(s):  
Youmin Hou ◽  
Miao Yu ◽  
Xuemei Chen ◽  
Zuankai Wang
Keyword(s):  
Liquid Film ◽  
Droplet Growth ◽  
Pinning Force ◽  
Dropwise Condensation ◽  
Ambient Conditions ◽  
Spherical Droplet ◽  
Design And Optimization ◽  
Morphology Transition ◽  
Hydrophobic Coating ◽  
Condensed Water

Recent advances in condensing surfaces with hybrid architectures of superhydrophobic/hydrophilic patterns allow us to decrease the nucleation energy barrier and spatially control the water condensation. However, the condensed water is susceptible to the large pinning force of the hydrophilic area, leading to an ultimate flooding. Here, we demonstrate a hierarchical nanostructured surface with patterned high wetting contrast to achieve a natural transition from filmwise-to-dropwise condensation, which reconciles the existing problems. The energy-dispersive X-ray spectroscopy (EDX) indicates that the fluorinated hydrophobic coating conformably covers the nanostructures except for the tops of micropillars, which are covered by hydrophilic silicon dioxide (FIG 1), resulting in an extreme wetting contrast. Condensation on the hybrid surface was observed in the environmental scanning electron microscope (ESEM) and ambient conditions with controlled humidity. Water preferentially nucleates on the top of micropillars and exhibits a rapid droplet growth (FIG 2). The enhancement is attributed to the filmwise-to-dropwise transition induced by the unique architectures and wetting features of the hybrid surface (FIG 3). The water embryos initially nucleate on the hydrophilic tops and quickly grow to a liquid film covering the whole top area. Since the superhydrophobic surrounding confines the spreading of condensed water, the localized liquid film gradually transits to an isolated spherical droplet as it grows. Remarkably, the condensate morphology transition activates an unusual droplet self-propelling despite the presence of abundant hydrophilic patches. It is important to note that such coalescence-induced jumping is dependent on the size of hydrophilic patches, that is, for larger hydrophilic patches, the energy released by coalescence may not overcome the increased droplet pinning, resulting in an immobile coalescence (FIG 4). The droplet departure ensures the recurrence of filmwise-to-dropwise transition, thus prevents the water accumulation in continuous condensation. These visualizations reveal the undiscovered impact of heterogeneous wettability and architectures on the morphology transition of the condensed water, and provide important insights into the surface design and optimization for enhanced condensation.

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