How spider silk catches the morning dew
London, Feb 4: In a new study, scientists have figured out how spider silk is able to catch the morning dew, which may lead to the development of new materials that are able to capture water from the air.
According to a report in Nature News, the study examines the silk of the hackled orbweaver spider Uloborus walckenaerius.
"Bright, pearl-like water drops hang on thin spider silk in the morning after fogging," said study author Lei Jiang from the Beijing National Laboratory for Molecular Sciences. "It is unexpected and interesting. Human hair can't do that," Jiang added.
Dry spider silk forms a necklace-like structure.
Two main fibres support a series of separate rounded 'puffs', each made up of tiny, randomly intertwined nanofibrils.
When water vapour condenses onto these puffs, they shrink into densely packed knots, shaped like spindles.
Thinner connecting stretches of nanofibrils, separating the knots, become more apparent; these areas are called 'joints'.
The researchers studied the webs under both electron and light microscopes.
They noticed that as water condenses on the web, droplets move towards the nearest spindle-knot, where they coalesce to form larger drops.
The spindle-knots have a rough surface, because the fibrils within them are randomly interweaved.
But, the joints between the knots have a smooth texture, because their constituent fibrils run parallel to each other.
It is this difference in roughness that helps water drops to slide towards the spindle-knots, sticking when they arrive.
The cone shape of the spindle-knots also drives droplets towards their centre.
Once they hit the edge of a cone, drops are propelled towards its base, the least curved region, because of the pressure difference caused by surface tension.
Guided by their findings, the team made their own artificial spider silk using nylon fibres dipped in a polymer solution that, when dried, formed spindle-knots similar to those in natural spider silk.
They anticipate that their studies of these fibres could lead to new materials for collecting water from the air.
Copyright Asian News International/DailyIndia.com