February 4, 2010

Spiders May Help Water Starved Countries

A spider may be the reason fog-catching nets, which provide precious water in rain-starved parts of the world, may be ready for a high-tech upgrade.

Chinese scientists reported their research in the journal Nature on why spider's silk is not only famous for strength but also terrific for collecting water from the air, sparing the creature the hunt for a drink.

The secret lies in the silk's tail-shaped protein fibers that change structure in response to water.

The tiny section of thread scrounges up into knots once it comes in contact with humidity.  The knots randomly arrange nanofibers that provide a rough, knobby texture.

Between the "spindle knots" are joints that are smooth and slender.

Small droplets then condense randomly on the spider's web.  Once the drops reach a critical size, surface tension causes them to slide along the slick-surfaced joints.

According to the report, the droplets then reach the spindle knots, where they coalesce with larger drops.

The joints are then freed up to begin a new cycle of condensation and water collection.

The team looked at the silk made by the cribellate spider, which uses a little comb to separate fibers and spin them into various kinds.

Once the scientists made observations, they fabricated fibers to replicate the silk's microscopic structure.

"Our artificial spider silk not only mimics the structure of wet-rebuilt spider silk but also its directional water collection capability," they claim.

They believe that the breakthrough will help develop man-made fibers that will help water collection and could also be used in manufacturing processes to snare airborne droplets.

Fog collection results in stretching out nets, or canvas, on poles and using the mesh to catch moisture from the breeze.  The runoff is collected in a pipe or a trough on the ground.

The technique was pioneered in the coastal Andes.  It is being encouraged in poor, dry parts of the world like Nepal.  It is also being promoted by charities as a useful tool to offset water stress that global warming causes.


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