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hydrophobic-surfaces
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Electroosmotic flow in hydrophobic microchannels of general cross section
, Article Journal of Fluids Engineering, Transactions of the ASME ; Volume 138, Issue 3 , 2016 ; 00982202 (ISSN) ; Sadeghi, A ; Saidi, M. H ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2016
Abstract
Adopting the Navier slip conditions, we analyze the fully developed electroosmotic flow in hydrophobic microducts of general cross section under the Debye-Hückel approximation. The method of analysis includes series solutions which their coefficients are obtained by applying the wall boundary conditions using the least-squares matching method. Although the procedure is general enough to be applied to almost any arbitrary cross section, eight microgeometries including trapezoidal, double-trapezoidal, isosceles triangular, rhombic, elliptical, semi-elliptical, rectangular, and isotropically etched profiles are selected for presentation. We find that the flow rate is a linear increasing...
Mixed pressure and AC electroosmotically driven flow with asymmetric wall zeta potential and hydrophobic surfaces
, Article ASME 2013 Heat Transfer Summer Conf. Collocated with the ASME 2013 7th Int. Conf. on Energy Sustainability and the ASME 2013 11th Int. Conf. on Fuel Cell Science, Engineering and Technology, HT 2013 ; Volume 1 , 2013 ; 9780791855478 (ISBN) ; Sharif University of Technology
2013
Abstract
The present study examines Alternating Current (AC) electroosmotic flows in a parallel plate microchannel subject to constant wall temperature. Numerical method consists of a central finite difference scheme for spatial terms and a forward difference scheme for the temporal term. Asymmetric boundary conditions are assumed for Poison-Boltzmann equation for determining the electric double layer (EDL) potential distribution. The potential distribution is then used to evaluate the velocity distribution. The velocity distribution is obtained by applying slip boundary conditions on the walls which accounts for probable hydrophobicity of surfaces. After determining the velocity distribution...
Superhydrophobic surfaces with a dual-layer micro- and nanoparticle coating for drag reduction
, Article Energy ; Volume 125 , 2017 , Pages 1-10 ; 03605442 (ISSN) ; Moosavi, A ; Nouri Borujerdi, A ; Daeian, M. A ; Vafaeinejad, S ; Sharif University of Technology
Elsevier Ltd
2017
Abstract
We propose a facile and cost effective method for fabricating superhydrophobic surfaces with significant drag reduction in a wide velocity range. A dual structure superhydrophobic aluminum surface with a hydrophobic Al2O3micro- and nanoparticle coating and also another superhydrophobic surface with a nanoparticle layer coating are fabricated. Then, the resulted drag from each of these surfaces is measured carefully in different velocities and compared with the drag of the as-received aluminum surface. Our results reveal that the surface with the dual structure experiences drag reduction in a wider velocity range compared with the nanoparticle coated sample. Drag reduction of the dual...
Surface wettability effect on the rising of a bubble attached to a vertical wall
, Article International Journal of Multiphase Flow ; Volume 109 , 2018 , Pages 178-190 ; 03019322 (ISSN) ; Davoudian, S. H ; Sharif University of Technology
Abstract
This paper deals with the dynamics of rising bubbles attached to a vertical wall under different wettability conditions. Even though, bubbles rising freely in a liquid have extensively been studied, bubbles attached to a wall have not been fully understood. Therefore, in this work, rising bubbles attached to a vertical wall were numerically investigated by applying the ALE method along with adaptive mesh refinement schemes to properly resolve the bubble interface and its deformation. To consider wall wettability effects, different contact angles of 45° 90° and 105° were considered along with the case of freely rising bubbles. The problem was carried out at different Bond numbers of 0.27,...
Molecular dynamics study of friction reduction of two-phase flows on surfaces using 3d hierarchical nanostructures
, Article Journal of Physical Chemistry C ; 2019 ; 19327447 (ISSN) ; Moosavi, A ; Kazemzadeh Hannani, S ; Sharif University of Technology
American Chemical Society
2019
Abstract
The use of superhydrophobic surfaces is one the most promising methods for reducing the friction and increasing the flow rate in fluid transfer systems. Because in such systems the surface structure plays a key role, in this study, we explore the performance of the hierarchical nanostructures. These nanostructures are inspired by the superhydrophobic surface of the lotus leaf. We consider a flow between two walls with hierarchical nanostructures and simulate the system via the molecular dynamics method. The size of the nanostructures and the distance between them have been studied to find whether a design with a maximum flow rate exists. The nanostructures have two parts, a bigger part on...
Molecular dynamics study of friction reduction of two-phase flows on surfaces using 3d hierarchical nanostructures
, Article Journal of Physical Chemistry C ; 2019 ; 19327447 (ISSN) ; Moosavi, A ; Hannani, S. K ; Sharif University of Technology
American Chemical Society
2019
Abstract
The use of superhydrophobic surfaces is one the most promising methods for reducing the friction and increasing the flow rate in fluid transfer systems. Because in such systems the surface structure plays a key role, in this study, we explore the performance of the hierarchical nanostructures. These nanostructures are inspired by the superhydrophobic surface of the lotus leaf. We consider a flow between two walls with hierarchical nanostructures and simulate the system via the molecular dynamics method. The size of the nanostructures and the distance between them have been studied to find whether a design with a maximum flow rate exists. The nanostructures have two parts, a bigger part on...
Sustainable superhydrophobic branched hierarchical ZnO nanowires: Stability and wettability phase diagram
, Article Applied Surface Science ; Volume 561 , 2021 ; 01694332 (ISSN) ; Bayat, A ; Rahemi Ardekani, S ; Saievar Iranizad, E ; Zaker Moshfegh, A ; Sharif University of Technology
Elsevier B.V
2021
Abstract
Stability of Cassie-Baxter (CB) state is very critical in application of superhydrophobic surfaces. The most industrial applications of superhydrophobic surfaces are limited by the transition from the CB state to Wenzel (W) state. In this research, CB state stability of branched hierarchical ZnO nanowires (BH-ZnO NWs) was investigated as compared with ZnO nanowires (ZnO NWs) by using theoretical and experimental approaches. For this purpose, surface of the BH-ZnO NWs and ZnO NWs were modified by thin layers of methyltrimethoxysilane (MTMS). The MTMS thickness was optimized by varying NH4F (0, 5, 10, 20 μL) as used catalyst. The highest water contact angle (WCA) was measured at about 153 ± 3°...
Drag reduction in internal turbulent flow by fabricating superhydrophobic Al2O3/waterborne polyurethane coatings
, Article Surface and Coatings Technology ; Volume 421 , 2021 ; 02578972 (ISSN) ; Moosavi, A ; Nouri Boroujerdi, A ; Najafkhani, H ; Najafpour, S ; Sharif University of Technology
Elsevier B.V
2021
Abstract
Nowadays, increasing the CO2 emissions are one of the inevitable challenges in the world. In addition, in many industries, fossil fuels are the main source of energy demands which worsen the problem. Since in most applications, the performance and energy loss are highly affected by the drag force, many investigations have been proposed to improve the surface properties to moving surface against the water, and consequently, increasing drag reduction. To this end, one effective way is utilizing superhydrophobic coatings. In this study, we prepare two different superhydrophobic coatings using Al2O3 nanoparticles (NPs) modified by HMDS (1,1,1,3,3,3-Hexamethyldisilazane) and PDMS...
Friction reduction in a nanochannel with grafted poly(N-isopropylacrylamide) oligomers: A molecular dynamics study
, Article Physics of Fluids ; Volume 33, Issue 5 , 2021 ; 10706631 (ISSN) ; Moosavi, A ; Hannani, S. K ; Sharif University of Technology
American Institute of Physics Inc
2021
Abstract
Superhydrophobic surfaces have been used for reducing friction in micro- and nanochannels. In the present work, water flow between two carbon walls with nanostructures made of poly(N-isopropylacrylamide) via the molecular dynamics method has been studied. The structure of this polymer can change based on the temperature of the environment, so that by increasing the temperature the structure becomes hydrophobic. This property has been studied and the effect of multiple factors on the slip length is presented. The effects of the number of monomers in the polymer, the distance between the polymers, and the temperature on the flow field are investigated. The results reveal that the slip length...
Mechanically stable superhydrophobic nanostructured aluminum mesh with reduced water surface friction
, Article Nanotechnology ; Volume 32, Issue 19 , 2021 ; 09574484 (ISSN) ; Afzali, N ; Taghvaei, N ; Moosavi, A ; Sharif University of Technology
IOP Publishing Ltd
2021
Abstract
Superhydrophobic surfaces demonstrate significant characteristics which make them suitable for a wide variety of applications. In this study, we propose a facile, one-step, and cost-effective anodizing scheme using aluminum nitrate/stearic acid mixture solution to create a superhydrophobic surface on an aluminum mesh. The surface outperforms the surface anodized by the widely used oxalic acid solution in terms of superhydrophobicity and water-surface friction behavior. The proposed surface reduced the friction by 11% on average respective to the surface prepared by oxalic acid. The durability of the introduced superhydrophobic surface has also been investigated. The proposed surface retained...
Correlation between surface roughness and hydrophobicity of GLAD RF sputtered PTFE/W/Glass nanorod thin films
, Article Vacuum ; Vol. 101, issue , March , 2014 , p. 279-282 ; Ebrahimi, M ; Moshfegh, A. Z ; Sharif University of Technology
Abstract
In this research, we have used glancing angle deposition (GLAD) RF sputtering technique with various angular speeds ranging from 5 to 30 RPM to fabricate polytetrafluoroethylene (PTFE, Teflon) coated Tungsten on glass substrate for producing hydrophobic surface. According to scanning electron microscopy (SEM) observations, Tungsten nanorods were formed on the substrate with average diameter and length of about ∼50 nm and 300 nm, respectively. Hydrophobic property of W/Glass and PTFE/W/Glass systems was investigated by water contact angle measurements and we have found that the contact angle varied with the substrate angular speed. Maximum contact angle of 121 was measured for the...
Wettability properties of PTFE/ZnO nanorods thin film exhibiting UV-resilient superhydrophobicity
, Article Applied Surface Science ; Volume 341 , 2015 , Pages 92-99 ; 01694332 (ISSN) ; Ebrahimi, M ; Nourmohammadi, A ; Moshfegh, A. Z ; Sharif University of Technology
Elsevier
2015
Abstract
In this research, initially anodization process was used to fabricate ZnO nanorods on Zn substrate and then RF sputtering technique was applied to grow a thin layer of polytetrafluoroethylene (PTFE, Teflon) on the coated ZnO nanorods for producing a superhydrophobic surface. According to scanning electron microscopy (SEM) observations, ZnO nanorods were formed with average diameter and length of about ∼180 nm and 14 μm, respectively. Superhydrophilic property of ZnO nanorods and superhydrophobic property of PTFE/ZnO nanorods was investigated by water contact angle (WCA) measurements. It was found that the contact angle varied with the PTFE deposition time. The highest contact angle...
Facile fabrication of superhydrophobic nanocomposite coating using modified silica nanoparticles and non-fluorinated acrylic copolymer
, Article Polymer Bulletin ; Volume 75, Issue 10 , 2018 , Pages 4641-4655 ; 01700839 (ISSN) ; Esmaili, H ; Nazari, M ; Sharif University of Technology
Abstract
A superhydrophobic nanocomposite coating was fabricated using a simple procedure. The nanocomposite is composed of an acrylic copolymer and modified silica nanoparticles. The acrylic copolymer was prepared by free radical copolymerization of methyl methacrylate and dodeycl methacrylate monomers. Silica nanoparticles were synthesized and modified with an alkyl silane reagent, hexadecyltrimethoxysilane. A mixture of acrylic copolymer and modified silica nanoparticles, dispersed in dichloromethane, was then sprayed on glass and filter paper surface. Chemical composition and structure of the coatings were investigated by FTIR, FESEM, AFM, 1H-NMR and GPC. The wettability of the prepared coating...
Delivery of hydrophobic anticancer drugs by hydrophobically modified alginate based magnetic nanocarrier
, Article Industrial and Engineering Chemistry Research ; Volume 57, Issue 3 , 2018 , Pages 822-832 ; 08885885 (ISSN) ; Amin, S. S ; Hosseini, H ; Sharif University of Technology
American Chemical Society
2018
Abstract
Since most of the anticancer drugs have low solubility in water, the clinical use of them is limited unless by some modification the solubility increases or the drug is carried with a soluble compartment. To solve this problem, we prepared a magnetic nanocarrier with a hydrophobic surface based on oleic acid chains in which hydrophobic drug molecules such as doxorubicin hydrochloride (DOX) and paclitaxel (PTX) are easily adsorbed onto the surface. Since the drug molecules are physically adsorbed on the surface, large amounts of DOX (282 mg·g-1) and PTX (316 mg·g-1) were immobilized onto the nanocarrier. Then, the surface of the drug loaded magnetic core was covered by a smart pH-sensitive...
Pressure drop reduction of power-law fluids in hydrophobic microgrooved channels
, Article Physics of Fluids ; Volume 31, Issue 7 , 2019 ; 10706631 (ISSN) ; Moosavi, A ; Sharif University of Technology
American Institute of Physics Inc
2019
Abstract
Using hydrophobic surfaces is one of the efficient methods to preserve energy in fluid transfer systems. However, the studies have been concentrated on Newtonian fluids despite the wide applications of non-Newtonian fluids in daily life and many industries such as the biological, foodstuff, chemical, petroleum, cosmetic, and lab on a chip fields. In this study, we consider power-law fluids as a typical example of non-Newtonian fluids and investigate the effect of hydrophobic microgrooves on the pressure drop in channels by utilizing the phase field method. We demonstrate that the optimum size of the rectangular microgrooves in which the maximum pressure drop reduction (PDR) happens for both...
Droplet condensation and jumping on structured superhydrophobic surfaces
, Article International Journal of Heat and Mass Transfer ; Volume 134 , 2019 , Pages 680-693 ; 00179310 (ISSN) ; Moosavi, A ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
A complete cycle of droplet nucleation, growth, coalescence and jumping on different textured hydrophobic and superhydrophobic surfaces is studied for the first time, using a 2-D double distribution function thermal lattice Boltzmann method. First, droplet nucleation mechanism on smooth and rough surfaces is studied in detail. The results reveal the presence of cooled vapor layer instability in the condensation on completely smooth surfaces. However, on the rough surfaces and near the roughness a completely different mechanism is observed and the nucleation occurs on the roughness wedges. Also, the condensation on different textured surfaces with nominal contact angles θa=90°,120°,155° is...
Plasma based surface modication of poly (dimethylsiloxane) electrospun membrane proper for organ-on-a-chip applications
, Article Scientia Iranica ; Volume 26, Issue 2 , 2019 , Pages 808-814 ; 10263098 (ISSN) ; Saidi, M. S ; Moghadas, H ; Firoozabadi, B ; Sharif University of Technology
Sharif University of Technology
2019
Abstract
Electrospun porous membrane; Superhydrophilic surfaces; Superhydrophobic surfaces; Cell culture; Organ on a chip; Flexible membrane; Strong membrane; Surface modications
Plasma based surface modication of poly (dimethylsiloxane) electrospun membrane proper for organ-on-a-chip applications
, Article Scientia Iranica ; Volume 26, Issue 2 , 2019 , Pages 808-814 ; 10263098 (ISSN) ; Saidi, M. S ; Moghadas, H ; Firoozabadi, B ; Sharif University of Technology
Sharif University of Technology
2019
Abstract
onstructing of the scaffolds for cell culture applications has long been of interest for engineering researchers and biologist. In this study, a novel process is utilized for construction of suitable membrane with a high mechanical strength and appropriate surface behavior. Poly (dimethylsiloxane) (PDMS) is electrospun into fine fibers using poly (methyl methacrylate) (PMMA) as the carrier polymer in different weight ratios. Since the surface behavior of all PDMS substrates is moderately hydrophobic (120 < contact angle (CA) < 150), the electrospun membranes with higher PDMS ratios show slightly higher hydrophilicity. Direct plasma treatment is utilized to change the interfacial wettability...
Ferrofluid droplet manipulation using an adjustable alternating magnetic field
, Article Sensors and Actuators, A: Physical ; Volume 301 , 2020 ; Favakeh, A ; Sedighi, E ; Shafii, M. B ; Sharif University of Technology
Elsevier B.V
2020
Abstract
Magnetically actuated droplet manipulation offers a promising tool for biomedical and engineering applications, such as drug delivery, biochemistry, sample handling in lab-on-chip devices and tissue engineering. In this study, characteristics of an adjustable alternating magnetic field generated by a magnetic coil for droplet manipulation was investigated which enables more control on droplet transport, and it can be considered as a suitable alternative for moving magnets or an array of micro-coils. By adjusting the magnetic flux density, the duty cycle and applied magnetic frequency, the manipulation of water-based ferrofluid droplets with a bio-compatible surfactant for different volumes...
Influence of new superhydrophobic micro-structures on delaying ice formation
, Article Colloids and Surfaces A: Physicochemical and Engineering Aspects ; Volume 595 , 2020 ; Taeibi Rahni, M ; Javadi, K ; Davoudian, S. H ; Miller, R ; Sharif University of Technology
Elsevier B.V
2020
Abstract
Drop motion on different types of new proposed micro-structure surfaces has been numerically investigated to find the optimum structure in view point of ice formation delaying. The droplet automatically moves on the inclined surfaces due to gravity forces. To validate the numerical algorithm, three different bench mark problems have been considered. The results indicate that the present algorithm is trustable for the presented numerical simulations. Then the validated numerical approach has been used to simulate droplet motion on nine proposed superhydrophobic surfaces in the same conditions. Comparison the drop motion on different micro-structure surfaces at different time indicate that...