http://www.ndsu.edu/pubweb/chiwonlee/plsc211/student%20papers/article10/Korynta,%20Brittany%20Joy/0199_Nepenthes_pitcher_plant.jpg
In any system where liquid is handled or encountered,
unwanted liquid-surface interactions are usually a limiting factor. They
trigger blood clotting in biological interfaces, nucleate icing, create drag in
transport systems, and promote biofouling. We already know that the microstructure
of the lotus leaf and the coatings it has inspired are known to exhibit superhydrophobicity and self-cleaning when water rolls off of
them. Despite this, the technology is still plagued with problems which
restrict their practical application. They show poor performance with oils and
fail under pressure or mechanical damage such as abrasions or torsion. In order
to widen the range of application for these type of repellant surfaces, researchers
at the university of Harvard have created a similarly functional technology
inspired by the Nepenthes pitcher plant. Their new surface is essentially
omniphobic, is composed of low cost materials, and self heals.
The Nepenthes pitcher grows in environments where the soil
is poor in minerals such as nitrogen and phosphorous. In order to gain some of
these essential nutrients, the plants use visual, aromatic, and nectar lures in
order to get insects to crawl onto the lip of the pitcher. When the unsuspecting
insect is there, it loses its grip and falls to a watery grave. The secret to
the slipperiness of the pitcher is using a liquid as a lubricating film, rather
than air (in the instance of a lotus leaf), to serve as the slippery interface,
which causes the plant's prey to essentially hydroplane into the pitcher.
http://www.seas.harvard.edu/sites/default/files/images/news/SLIPS-fabric-schematic.jpg
The technology created by the scientists at Harvard is known
as Slippery Liquid-Infused Porous Surfaces or SLIPS for short. It is composed
of a solid porous matrix imbued with a liquid surface layer. This liquid film
acts as the interface between the material and any liquid interaction. The
technology is proving to be repellant to essentially everything and is more
mechanically stable that lotus leaf inspired equivalents.
Many existing liquid repellent surfaces rely on the micro
and nanostructure of the material, if they are damaged, they permanently lose their
repellent properties. Since SLIPS uses a liquid layer to provide the
slipperiness of the material, if the solid matrix is damaged, the fluid will
fill in the gaps and essentially self-heal. Also, because the technology does
not rely on a layer of air to repel liquids, it performs just as well under
high pressure environments. It can even be used to create stain free clothes by
infusing the fibers with the liquid.
http://www.otd.harvard.edu/technologies/images/3983_a.jpg
Due to the versatility and robustness of the material, it
could be used in a wide variety of applications. One of these is in the medical
field were the coating could be applied to devices ranging from catheters,
which would benefit from low drag and the biofouling properties, and micro-fluidic
devices where SLIPS could reduce the drag, and thus amount of blood or time,
needed to run tests. Since SLIPS also prevents ice formation, it would be
invaluable to aircraft and refrigeration industries. Ice formation can delay
flights and is a major contributor to refrigeration inefficiencies.
SLIPS has also been shown to work at up to 675 atm , which
would allow it to be used in both normal atmospheric conditions and hazardous
conditions such as in oil extraction or deep earth exploration. Finally, the
matrix can be made so that the size of the material is smaller than the
wavelength of visible light. This would provide an optically transparent
coating which could then be applied things like car windshields or avionic
cockpits.
If you would like to see the anti-frosting properties of SLIPS or would like to see other demos, follow the link below or go to SlipperySurfaces YouTube channel.
helped alot :)
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