scholarly journals Tip-induced flipping of droplets on Janus pillars: From local reconfiguration to global transport

2020 ◽  
Vol 6 (28) ◽  
pp. eabb4540 ◽  
Author(s):  
Shile Feng ◽  
Joachim Delannoy ◽  
Antoine Malod ◽  
Huanxi Zheng ◽  
David Quéré ◽  
...  
Keyword(s):  
Long Range ◽  
Wide Spectrum ◽  
Solid Surfaces ◽  
Water Repellent ◽  
Local Geometry ◽  
Original Design ◽  
Synthetic Materials ◽  
Global Transport ◽  
Elastic Forces ◽  
Original Phenomenon

Despite their simplicity, water droplets manifest a wide spectrum of forms and dynamics, which can be actuated using special texture at solid surfaces to achieve desired functions. Along this vein, natural or synthetic materials can be rendered water repellent, oleophobic, antifogging, anisotropic, etc.—all properties arising from an original design of the substrate and/or from the use of special materials promoting capillary or elastic forces at the droplet scale. Here, we report an original phenomenon occurring at the tip of asymmetric (half-flat, half-curved) pillars: Droplets reconfigure and get oriented on the curved side of these Janus tips. This local, geometry-driven effect, namely, tip-induced flipping of droplets, is found to be generic and have spectacular global consequences: Vast assemblies of Janus pillars enable a continuous, long-range, and fast self-transport of water harvested from fogs, which makes it possible to collect and concentrate droplets at different scales.

Polydimethylsiloxane as a Tooth Surface-Bound Carrier of Triclosan: a New Concept in Chemical Plaque Inhibition

1994 ◽  
Vol 8 (2) ◽  
pp. 272-277 ◽  
Author(s):  
G. Rølla ◽  
J.E. Ellingsen ◽  
D. Gaare
Keyword(s):  
Silicone Oil ◽  
Dental Enamel ◽  
Solid Surfaces ◽  
Tooth Surface ◽  
Water Repellent ◽  
Streptococcus Sobrinus ◽  
Gingival Health ◽  
Low Solubility

Polydimethylsiloxane (silicone oil) has an extremely low surface tension: It spreads over solid surfaces and forms a tenacious film which is hydrophobic and water-repellent. It is known that this liquid binds to hydroxyapatite and to dental enamel and changes the properties of these solids. It has been suggested that silicone oil may be applied to teeth and serve as a reservoir of lipid-soluble antibacterial substances which presumably will be slowly released into saliva due to their low solubility in water. The present paper reviews recent papers where this hypothesis is tested in vitro and in vivo. It was first shown that test tubes treated with the combination silicone oil and the lipid-soluble agent triclosan acquired a layer which inhibited bacterial growth in a culture of Streptococcus sobrinus (OMZ 176) which was grown in sucrose. Both growth in the medium and polysaccharide adsorption to the glass wall were inhibited. Silicone oil alone inhibited polysaccharide adsorption to some degree, whereas the growth in the medium was not affected. In a similar clinical plaque-inhibition study, topical application of silicone oil/triclosan to the teeth of a test panel showed marked plaque inhibition, particularly giving an increased number of teeth with scores of 0 (no plaque). In a study where silicone oil and triclosan were incorporated into a toothpaste, improved gingival health was observed after a period of one month. It is concluded that the use of silicone oil/ triclosan in the manner described above represents a new principle in preventive dentistry. The results obtained seem to warrant further experiments with this combination.

Electret mechanism of the long-range effect of solid surfaces

1969 ◽  
Vol 56 (6) ◽  
pp. 325-325 ◽  
Author(s):  
G. I. Distler ◽  
S. A. Kobzareva
Keyword(s):  
Long Range ◽  
Solid Surfaces ◽  
Range Effect

scholarly journals From Extremely Water-Repellent Coatings to Passive Icing Protection—Principles, Limitations and Innovative Application Aspects

Coatings ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 66 ◽  
Author(s):  
Karekin D. Esmeryan
Keyword(s):  
Primary Objective ◽  
Snow Accumulation ◽  
Cold Climate ◽  
Solid Surfaces ◽  
Water Repellent ◽  
Ice Accretion ◽  
Physical Mechanisms ◽  
Ice Nuclei ◽  
Engineering Sciences ◽  
High Voltage Power Lines

The severe environmental conditions in winter seasons and/or cold climate regions cause many inconveniences in our routine daily-life, related to blocked road infrastructure, interrupted overhead telecommunication, internet and high-voltage power lines or cancelled flights due to excessive ice and snow accumulation. With the tremendous and nature-inspired development of physical, chemical and engineering sciences in the last few decades, novel strategies for passively combating the atmospheric and condensation icing have been put forward. The primary objective of this review is to reveal comprehensively the major physical mechanisms regulating the ice accretion on solid surfaces and summarize the most important scientific breakthroughs in the field of functional icephobic coatings. Following this framework, the present article introduces the most relevant concepts used to understand the incipiency of ice nuclei at solid surfaces and the pathways of water freezing, considers the criteria that a given material has to meet in order to be labelled as icephobic and clarifies the modus operandi of superhydrophobic (extremely water-repellent) coatings for passive icing protection. Finally, the limitations of existing superhydrophobic/icephobic materials, various possibilities for their unconventional practical applicability in cryobiology and some novel hybrid anti-icing systems are discussed in detail.

scholarly journals Spreading of non volatile liquids on smooth solid surfaces : role of long range forces

1988 ◽  
Vol 23 (6) ◽  
pp. 1047-1054 ◽  
Author(s):  
L. Léger ◽  
M. Erman ◽  
A.M. Guinet-Picart ◽  
D. Ausserre ◽  
C. Strazielle ◽  
...  
Keyword(s):  
Long Range ◽  
Solid Surfaces ◽  
Volatile Liquids

A quick fix for modeling infiltration in water-repellent soils

2021 ◽  
Author(s):  
Ryan Stewart ◽  
Majdi R. Abou Najm ◽  
Simone Di Prima ◽  
Laurent Lassabatere
Keyword(s):  
Soil Water ◽  
Wide Spectrum ◽  
Correction Term ◽  
Water Repellency ◽  
Infiltration Rate ◽  
Water Repellent ◽  
Soil Water Repellency ◽  
Simple Method ◽  
Wide Range ◽  
Infiltration Models

<p>Water repellency occurs in soils under a wide spectrum of conditions. Soil water repellency can originate from the deposition of resinous materials and exudates from vegetation, vaporization and condensation of organic compounds during fires, or the presence of anthropogenic-derived chemicals like petroleum products, wastewater or other urban contaminants. Its effects on soils range from mild to severe, and it often leads to hydrophobic conditions that can significantly impact the infiltration response with effects extending to the watershed-scale. Those effects are often time-dependent, making it a challenge to simulate infiltration behaviors of water-repellent soils using standard infiltration models. Here, we introduce a single rate-constant parameter (α<sub>WR</sub>) and propose a simple correction term (1-e<sup>-αWRt</sup>) to modify models for infiltration rate. This term starts with a value of zero at the beginning of the infiltration experiment (t = 0) and asymptotically approaches 1 as time increases, thus simulating a decreasing effect of soil water repellency through time. The correction term can be added to any infiltration model (one- two- or three-dimensional) and will account for the water repellency effect. Results from 165 infiltration experiments from different ecosystems and wide range of water repellency effects validated the effectiveness of this simple method to characterize water repellency in infiltration models. Tested with the simple two-term infiltration equation developed by Philip, we obtained consistent and substantial error reductions, particularly for more repellent soils. Furthermore, results revealed that soils that were burned during a wildfire had smaller α<sub>WR</sub> values compared to unburned controls, thus indicating that the magnitude of α<sub>WR</sub> may have a physical basis.</p>

scholarly journals ELASTIC CURVES AND SURFACES UNDER LONG-RANGE FORCES: A GEOMETRIC APPROACH

2013 ◽  
Vol 27 (12) ◽  
pp. 1350043 ◽  
Author(s):  
J. A. SANTIAGO ◽  
G. CHACÓN-ACOSTA ◽  
O. GONZÁLEZ-GAXIOLA
Keyword(s):  
Long Range ◽  
Normal Force ◽  
Geometric Approach ◽  
Curves And Surfaces ◽  
Elastic Curves ◽  
Force Coupling ◽  
Long Range Interactions ◽  
Elastic Forces ◽  
Shape Equation ◽  
The Mean

Using classical differential geometry, the problem of elastic curves and surfaces in the presence of long-range interactions Φ, is posed. Starting from a variational principle, the balance of elastic forces and the corresponding projections ni⋅∇Φ, are found. In the case of elastic surfaces, a force coupling the mean curvature with the external potential, KΦ, appears; it is also present in the shape equation along the normal principal in the case of curves. The potential Φ contributes to the effective tension of curves and surfaces and also to the orbital torque. The confinement of a curve on a surface is also addressed, in such a case, the potential contributes to the normal force through the terms -κΦ-n⋅∇Φ. In general, the equation of motion becomes integro-differential that must be numerically solved.

Long-range global transport and characterization of dust

2022 ◽  
pp. 483-504
Author(s):  
Ashwini Kumar ◽  
Garima Shukla ◽  
Arvind Singh
Keyword(s):  
Long Range ◽  
Global Transport

scholarly journals Addressing the importance of microplastic particles as vectors for long-range transport of chemical contaminants: perspective in relation to prioritizing research and regulatory actions

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Todd Gouin
Keyword(s):  
Physicochemical Properties ◽  
Long Range ◽  
Environmental Fate ◽  
Polar Regions ◽  
Chemical Contaminants ◽  
Toxicological Effects ◽  
Atmospheric Particulates ◽  
Source Regions ◽  
Global Transport ◽  
Range Transport

AbstractOver the last several years there has been increasing concern regarding the environmental fate and potential global transport of plastic debris, particularly in the form of microplastic particles (MPs). The global transport of MPs has also triggered concerns regarding the potential role that its mobility may represent towards influencing the long-range environmental transport (LRET) of particle-bound chemicals, particularly the large number of chemicals known to be added to plastic. This perspective considers the various lines-of-evidence that might be used towards understanding the LRET of persistent organic pollutants (POPs). For instance, it has been proposed that the LRET of POPs is facilitated by global fractionation processes that facilitate the mobility of chemicals from source regions towards remote locations, such as the polar regions, where they have the potential to accumulate. These processes are influenced by the physicochemical properties of POPs and can result in various transport mechanisms influencing environmental fate and transport. Here I suggest that there are similarities that can be drawn, whereby knowledge of how differences in the physicochemical properties of MPs relative to different emission scenarios, can influence the relative importance of sequestration processes that may result in global fractionation of MPs. Several challenges are identified throughout the perspective, with an urgent need towards the development and application of standard sampling and analytical methods being identified as critical for enabling datasets to be reliably compared for use in better understanding potential source-receptor relationships, as well as advancing the characterization and quantification of various environmental fate processes. In many instances, it is suggested that advances in our understanding can be facilitated based on knowledge obtained in other areas of research, such as in relation to studies developing tools to evaluate the mobility of particulate organic matter in aqueous environments or from studies investigating the fate and mobility of atmospheric particulates. Recognizing that not all MPs are equal, with respect to environmental fate and toxicological effects, knowledge regarding which types of MPs are likely to be subject to LRET can only strengthen our ability to evaluate their role as vectors of transport for plastic associated chemicals and the associated risks that their LRET may represent. Nevertheless, several outstanding issues remain that would benefit from constructive discussions between all stakeholders. It is anticipated that this perspective can play a role in initiating those discussions.

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