Harvesting Liquid Water in Fog - Part II

Mankind has made significant strides towards harvesting from the 2% of water in the air that exists in liquid form. This progress comes from artificially replicating nature's inventions like the back of the African Stenocara beetle. Other moisture capturing systems are found in nature's designs for the Texas Thorny Devil Lizard, the structure of Cactus thorns and the structure of the leaves of plants like the Welwitschia Mirabilis.

Bio-mimicry & Species Adaptation

Stenocara Beetle
(Image: www.rain-barrel.net)

The Stenocara beetle lives in the Namib Desert in Africa which has endured arid and semi-arid condition for over 55 million years, has less than 5mm of rain annually and is practically barren of vegetation. 

The only other sources of water are underground rivers and morning fog that moves in over the desert near the coast from the ocean. This fog travels at gale speeds a few times a month.

Microscopic Detail
(photo: Oxford University)

An inhabitant of the Namib Desert, the Stenocara Beetle has evolved to harvest the liquid water in the fog through a combination of hydrophilic bumps/ridges and hydrophobic troughs/valleys on its back. 

To survive in the desert, Stenocara evolution has adapted it to catch the liquid water in the fog through a back of unique design . As described in http://www.biomimicryeuropa.org, "The peak of each bump is smooth and attracts water. Tiny rounded nodules, no wider than a human hair, cover the slopes of each bump and the troughs in between. The nodules are coated in a wax-like material, making them hydrophobic. When the fog rolls in, the beetle tilts its body into the wind. The water droplets from the fog are repelled from the nodules but stick to the peaks of the bumps. The droplets grow until they are large enough to roll down from the top of the peaks and are channeled to a spot on the beetle's back that leads straight to its mouth."

Design patent No. PCT/GB02/00067

Zoologists, led by Andrew Parker at Oxford University, discovered this hydrophilic-hydrophobic design and have obtained a design patent on it. Now the pace has quickened to find a commercial way to gain from nature's design of the Stenocara beetle's back.

The MIT Project

Chemical engineer Robert E. Cohen and materials scientist Michael F. Rubner have perfected a film with hydrophilic peaks and hydrophobic runways that extract liquid water from air and possibly go a step further in coalescing water vapor into liquid water. The next frontier is commercialization of this film for common use.

The University of Sydney Project

Australia, a country with few inland water resources, has nearly 90% of its population living in coastal cities. At the University of Sydney, a small team has a large goal - develop a film that can be laid on a large surface (like the side of a building or the roof of a house) that is similar in design to nature's design for the Stenocara's back with the very same water-harvesting functionality that nature has adapted for the survival of Stenocara and the propagation of its species

All this effort for 2% of the water contained in the air!