scholarly journals Sorting of droplets by migration on structured surfaces

2011 ◽  
Vol 2 ◽  
pp. 215-221
Author(s):  
Wilfried Konrad ◽  
Anita Roth-Nebelsick
Keyword(s):  
Contact Angle ◽  
Surface Energy ◽  
Droplet Diameter ◽  
Surface Pattern ◽  
Patterned Surfaces ◽  
Liquid Droplets ◽  
Structured Surfaces ◽  
Biological Surfaces ◽  
Gain Energy ◽  
Droplet Movement

Background: Controlled transport of microdroplets is a topic of interest for various applications. It is well known that liquid droplets move towards areas of minimum contact angle if placed on a flat solid surface exhibiting a gradient of contact angle. This effect can be utilised for droplet manipulation. In this contribution we describe how controlled droplet movement can be achieved by a surface pattern consisting of cones and funnels whose length scales are comparable to the droplet diameter. Results: The surface energy of a droplet attached to a cone in a symmetry-preserving way can be smaller than the surface energy of a freely floating droplet. If the value of the contact angle is fixed and lies within a certain interval, then droplets sitting initially on a cone can gain energy by moving to adjacent cones. Conclusion: Surfaces covered with cone-shaped protrusions or cavities may be devised for constructing “band-conveyors” for droplets. In our approach, it is essentially the surface structure which is varied, not the contact angle. It may be speculated that suitably patterned surfaces are also utilised in biological surfaces where a large variety of ornamentations and surface structuring are often observed.

scholarly journals Investigation of heat transfer during evaporation of droplets of Fe3O4 nanofluids from biphilic surfaces

2021 ◽  
Vol 2119 (1) ◽  
pp. 012083
Author(s):  
E M Starinskaya ◽  
N B Miskiv ◽  
M K Lei ◽  
V V Terekhov
Keyword(s):  
Heat Transfer ◽  
Contact Angle ◽  
Evaporation Rate ◽  
Experimental Studies ◽  
Spatial Gradient ◽  
Liquid Droplets ◽  
Structured Surfaces ◽  
Evaporation Temperature ◽  
Evaporation Of Droplets ◽  
Contact Angle Of Wetting

Abstract In this work, unique biphilic substrates were prepared with a sharp spatial gradient of the contact angle of wetting. Experimental studies of the process of evaporation of liquid droplets lying on the structured surfaces have been carried out. In the experiment, the dynamics of the temperature of an evaporating droplet was compared depending on its orientation in space. It was found that suspended droplets of 0.1 wt % Fe3O4 nanofluid have a higher evaporation temperature and a higher evaporation rate as compared to sessile droplets.

Comparative Study of Surface Energies of Native Oxides of Si(100) and Si(111) via Three Liquid Contact Angle Analysis

MRS Advances ◽  
2018 ◽  
Vol 3 (57-58) ◽  
pp. 3379-3390 ◽  
Author(s):  
Saaketh R. Narayan ◽  
Jack M. Day ◽  
Harshini L. Thinakaran ◽  
Nicole Herbots ◽  
Michelle E. Bertram ◽  
...  
Keyword(s):  
Contact Angle ◽  
Surface Energy ◽  
Sessile Drop ◽  
Surface Composition ◽  
Ion Beam ◽  
Contact Angles ◽  
Van Der Waals Interactions ◽  
Native Oxides ◽  
Relative Errors ◽  
Contact Angle Analysis

ABSTRACTThe effects of crystal orientation and doping on the surface energy, γT, of native oxides of Si(100) and Si(111) are measured via Three Liquid Contact Angle Analysis (3LCAA) to extract γT, while Ion Beam Analysis (IBA) is used to detect Oxygen. During 3LCAA, contact angles for three liquids are measured with photographs via the “Drop and Reflection Operative Program (DROP™). DROP™ removes subjectivity in image analysis, and yields reproducible contact angles within < ±1°. Unlike to the Sessile Drop Method, DROP can yield relative errors < 3% on sets of 20-30 drops. Native oxides on 5 x 1013 B/cm3 p- doped Si(100) wafers, as received in sealed, 25 wafer teflon boats continuously stored in Class 100/ISO 5 conditions at 24.5°C in 25% controlled humidity, are found to be hydrophilic. Their γT, 52.5 ± 1.5 mJ/m2, is reproducible between four boats from three sources, and 9% greater than γT of native oxides on n- doped Si(111), which averages 48.1 ± 1.6 mJ/m2 on four 4” Si(111) wafers. IBA combining 16O nuclear resonance with channeling detects 30% more oxygen on native oxides of Si(111) than Si(100). While γT should increase on thinner, more defective oxides, Lifshitz-Van der Waals interactions γLW on native oxides of Si(100) remain at 36 ± 0.4 mJ/m2, equal to γLW on Si(111), 36 ± 0.6 mJ/m2, since γLW arises from the same SiO2 molecules. Native oxides on 4.5 x 1018 B/cm3 p+ doped Si(100) yield a γT of 39 ± 1 mJ/m2, as they are thicker per IBA. In summary, 3LCAA and IBA can detect reproducibly and accurately, within a few %, changes in the surface energy of native oxides due to thickness and surface composition arising from doping or crystal structure, if conducted in well controlled clean room conditions for measurements and storage.

Addition of Cellulose Nanofibers to Control Surface Roughness for Hydrophobic Ceramic Coatings

2021 ◽  
Vol 21 (8) ◽  
pp. 4492-4497
Author(s):  
Eun Ae Shin ◽  
Gye Hyeon Kim ◽  
Jeyoung Jung ◽  
Sang Bong Lee ◽  
Chang Kee Lee
Keyword(s):  
Surface Roughness ◽  
Contact Angle ◽  
Surface Energy ◽  
Water Contact Angle ◽  
Ceramic Coating ◽  
Cellulose Nanofibers ◽  
Ceramic Coatings ◽  
Coating Material ◽  
Textured Surface ◽  
Water Contact

Hydrophobic ceramic coatings are used for a variety of applications. Generally, hydrophobic coating surfaces are obtained by reducing the surface energy of the coating material or by forming a highly textured surface. Reducing the surface energy of the coating material requires additional costs and processing and changes the surface properties of the ceramic coating. In this study, we introduce a simple method to improve the hydrophobicity of ceramic coatings by implementing a textured surface without chemical modification of the surface. The ceramic coating solution was first prepared by adding cellulose nanofibers (CNFs) and then applied to a polypropylene (PP) substrate. The surface roughness increased as the amount of added CNFs increased, increasing the water contact angle of the surface. When the amount of CNFs added was corresponding to 10% of the solid content, the surface roughness average of the area was 43.8 μm. This is an increase of approximately 140% from 3.1 μm (the value of the surface roughness of the surface without added CNFs). In addition, the water contact angle of the coating with added CNF increased to 145.0°, which was 46% higher than that without the CNFs. The hydrophobicity of ceramic coatings with added CNFs was better because of changes in the surface topography. After coating and drying, the CNFs randomly accumulated inside the ceramic coating layer, forming a textured surface. Thus, hydrophobicity was improved by implementing a rugged ceramic surface without revealing the surface of the CNFs inside the ceramic layer.

New method for determining paper surface energy per contact angle

Cellulose ◽  
2019 ◽  
Vol 26 (17) ◽  
pp. 9295-9309 ◽  
Author(s):  
Hind El Omari ◽  
El-houssaine Ablouh ◽  
François Brouillette ◽  
Moha Taourirte ◽  
Ahmed Belfkira
Keyword(s):  
Contact Angle ◽  
Surface Energy ◽  
New Method ◽  
Paper Surface

scholarly journals Sorting Liquid Droplets by Surface Tension Using Devices with Quasi-Superamphiphobic Coatings

Polymers ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 820 ◽  
Author(s):  
Yu-Ping Zhang ◽  
Di Fan ◽  
Xiu-Zhi Bai ◽  
Cheng-Xing Cui ◽  
Jun Chen ◽  
...  
Keyword(s):  
Surface Tension ◽  
Surface Energy ◽  
Solid Surface ◽  
Glass Slide ◽  
Liquid Droplets ◽  
Surface Tensions ◽  
Coated Nanoparticles ◽  
Tilting Angle ◽  
Time Distance ◽  
Alcoholic Strength

Any solid surface with homogenous or varying surface energy can spontaneously show variable wettability to liquid droplets with different or identical surface tensions. Here, we studied a glass slide sprayed with a quasi-superamphiphobic coating consisting of a hexane suspension of perfluorosilane-coated nanoparticles. Four areas on the glass slide with a total length of 7.5 cm were precisely tuned via ultraviolet (UV) irradiation, and droplets with surface tensions of 72.1–33.9 mN m−1 were categorized at a tilting angle of 3°. Then, we fabricated a U-shaped device sprayed with the same coating and used it to sort the droplets more finely by rolling them in the guide groove of the device to measure their total rolling time and distance. We found a correlation between ethanol content/surface tension and rolling time/distance, so we used the same device to estimate the alcoholic strength of Chinese liquors and to predict the surface tension of ethanol aqueous solutions.

Influence of argon plasma treatment on carbon fibre reinforced high performance thermoplastic composite

2020 ◽  
pp. 095400832095706
Author(s):  
Jennifer Vinodhini ◽  
K Sudheendra ◽  
Meera Balachandran ◽  
Shantanu Bhowmik
Keyword(s):  
Mechanical Properties ◽  
Contact Angle ◽  
Surface Energy ◽  
Carbon Fibre ◽  
Plasma Treatment ◽  
Dynamic Contact Angle ◽  
Argon Plasma ◽  
Dynamic Contact ◽  
Resin Matrix ◽  
Surface Modified

This investigation highlights argon plasma treatment on Poly-aryl-ether-ketone (PAEK) and carbon fibre (CF) surface. The PAEK and CF surface is modified for 300 sec and the change in physiochemical and mechanical properties were investigated through Fourier Transform Infrared Spectroscopy (FTIR), Dynamic Contact angle, Atomic Force Microscope (AFM) and Tensile Test. FTIR of surface modified PAEK revealed the stretching of C-H, C=C and C=O functional groups. A reversal phenomenon of increased surface energy was observed through dynamic contact angle study of CF and to further examine the surface energy effect, AFM analysis on CF was carried out revealing increased roughness with numerous micro dents formation. PAEK/CF composite samples were fabricated through compression moulding technique. The change in mechanical properties due to surface modification were analysed through Tensile testing on surface modified PAEK/CF sample and untreated PAEK/CF samples. The surface treated PAEK/CF showed increased tensile strength than untreated PAEK/CF. The argon plasma treatment helped in creating depth striations that lead to better interlocking of resin matrix with the reinforced CF. The fracture surface was examined through Filed Emission Scanning Electron Microscope (FE-SEM) wherein the Micrographs of the tensile tested samples indicated failure of composite due to fibre breakage.

Preparation of Hydrophobic Nylon Fabric

2016 ◽  
Vol 11 (1) ◽  
pp. 155892501601100
Author(s):  
Jinmei Du ◽  
Lulu Zhang ◽  
Jing Dong ◽  
Ying Li ◽  
Changhai Xu ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Contact Angle ◽  
Surface Energy ◽  
Water Contact Angle ◽  
Sem Images ◽  
Water Contact ◽  
Carboxyl Content ◽  
Factors Affecting ◽  
Nylon Fabric ◽  
Butanetetracarboxylic Acid

Surface roughness and surface energy are two important factors affecting the hydrophobicity of nylon fabric. In this study, nylon fabric was treated for hydrophobicity with tetrabutyltitanate (TBT) and octadecylamine (OA) which were respectively responsible for increasing surface roughness and reducing surface energy. In order to enhance the hydrophobicity, In order to further enhance hydrophobicity by increasing available reactive sites, 1,2,3,4–butanetetracarboxylic acid (BTCA) was applied as a pretreatment to the nylon fabric It was found that the carboxyl content of nylon was increased by the BTCA pretreatment. SEM images showed that the TBT treatment produced small particles on nylon fabric which made surface rough. The water contact angle of nylon fabric treated with BTCA, TBT and OA was measured to be 134°, which was much greater than the water contact angle of nylon fabric treated only with OA. This indicated that the surface roughness resulting from the TBT treatment played an important role in improving hydrophobicity of the treated nylon fabric. The resistance to water penetration and the repellency of water spray of nylon fabric treated with BTCA, TBT and OA were respectively measured to be 27.64 mbar and 85 out of 100.

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