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Surface tension is one of the research topics in biomimetics. Oil and water don’t mix, as you’ve seen. You and I get wet, but ducks don’t. Water binds to mercury but does not wet the glass, oil climbs a cotton wick against gravity; sap and water ascend to the tops of tree leaves, and paintbrush hair doesn’t cling together when dry or even when dipped in water but forms a fine tip when removed. All of these occurrences and a bunch of others are connected to the free surfaces of liquids. When liquids are poured into a container, they acquire a free surface since they have no defined shape, but have a specified volume. These surfaces have a little extra boost. Surface tension is the term for this phenomenon, which only applies to liquids because gases do not have free surfaces. Let’s look at how surface tension works in water.
What is Surface Tension Biomimetics?
The study of nature and natural occurrences with the objective of understanding underlying mechanisms, acquiring ideas from nature and applying concepts to science, engineering, and medicine is known as biomimetics. Fluid-drag-reduction swimsuits inspired by the structure of shark skin, velcro closures inspired by burrs, aeroplane shapes inspired by the appearance of birds, and stable building constructions inspired by the backbone of turban shells are just a few examples of biomimetic research.
Only below length scales of the order of the fluid’s capillary length, which for water is roughly 2 millimetres, will surface tension forces begin to dominate gravity forces. Because of this scaling, biomimetic devices that rely on surface tension will often be very small, but they can be used in a variety of ways.
The Surface tension of water
At ambient temperature, the surface tension of water is around 72 mN/m, making it one of the highest surface tensions for a liquid. Only mercury, liquid metal with a surface tension of over 500 mN/m, has a higher surface tension than any other liquid.
Water has a higher surface tension than most other liquids due to the relatively high attraction of water molecules to each other through a web of hydrogen bonds. Water has the highest surface tension of all liquids, aside from mercury, due to hydrogen bonding in water molecules. Water molecules near the liquid’s surface (in contact with air) are held close together by surface tension, forming an invisible film. Surface tension is required for the passage of energy from the wind to the water for waves to form. In lakes and seas, waves are required for rapid oxygen diffusion. Water has the highest surface tension of any commonly occurring liquids, second only to mercury.
Water’s high surface tension is significant on two levels. First, below a length scale of about 1mm, surface tension forces outweigh gravitational and viscous forces, resulting in a practically impenetrable barrier at the air-water interface. This becomes a crucial element in minuscule insects’, bacteria’s, and other microorganisms’ environments and lifestyles. Second, surface tension plays an important impact in the solvent characteristics of water at the molecular scale (A nanometer is one-billionth of a metre and ranges from 0.1 to 100 nm). Water’s high dielectric constant is also essential in its ability to act as a solvent. Though significant, the biological relevance of water expansion upon chilling and freezing is mostly indirect due to geophysical factors such as ocean and lake freezing, the creation of the polar ice cap, and weathering through freeze-thaw cycles.
Water striders, for example, use surface tension to walk on a pond’s surface in the following manner. Because the water molecules and the molecules of the water strider’s leg have no link. When the leg presses down on the water, the water’s surface tension tries to regain its flatness due to the deformation of the leg. The water’s behaviour pulls the water strider upward, allowing it to stand on the surface as long as its mass is small enough for the water to support it. The water’s surface acts as an elastic film, with the insect’s feet creating indentations in the surface, increasing the surface area of the water. The insect’s feet, on the other hand, are pushed higher by the water’s tendency to minimise surface curvature (space).
Conclusion
Surface tension is the amount of energy necessary to raise the surface area by a certain quantity. The requirement for this to happen is that strong intermolecular interactions exist between distinct liquid particles. The phenomenon known as surface tension is caused by the cohesive forces between liquid molecules. Because other water molecules do not entirely encircle the molecules at the surface of a glass of water on all sides, they are called surface molecules. They cohere more strongly with those directly related to them (in this case, next to and below them, but not above). It is not true that a “skin” forms on the surface of the water. The stronger cohesiveness between water molecules, as opposed to the attraction of water molecules to the air. It is more difficult to move an object through the surface than it is to move it while completely immersed.
