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Biomimetics of Water

Posted by John Jackson Aug 19, 2011

Andrew Parker is a Research Leader in the Crustacea Research Group in the NHM Zoology Department.  He writes:

Animals and plants capture or store water in efficient ways where water is scarce. This research into biomimetics of water has the ultimate aim to manufacture devices that can collect, filter and store water in dry regions of the Earth, which are set to expand rapidly with the progression of climate change.

This work falls into the subject of biomimetics – extracting good design from nature. It involves a collaboration with physicists, chemists, mathematicians and engineers at the Massachusetts Institute of Technology (MIT), which was instigated by National Geographic magazine, who dedicated a feature article to the independent but uniquely related work of the MIT and NHM groups (April 2008).

The subjects we cover are diverse, and include the water collecting mechanisms in various beetles and lizards, hydrophobic and hydrophilic surfaces in plants, and the mechanisms by which diving birds can maintain an air layer beneath their feathers while submerged. Within the physical sciences, we consider the mechanics of flow in fluids, and the interaction of fluids with surfaces, including hydrophobic, hydrophilic and pining behaviours of fluid drops, such as that observed when dew drops cling to certain leaves.

Our research begins with electron microscopy to understand the 3D architecture of the biological surfaces at the micron and nano levels. In other, specialized microscopes, drops of water and other liquids (with different fluidic characteristics) are placed on the biological surfaces and their “contact angles” are measured. This provides data on how well different liquids “ball up”, and therefore the degree of water repellency, for instance. Then, calculations are made to explain how each biological surface is responsible for its precise water properties. From here, new surfaces can be designed to solve precise liquid problems in industry, along with solving water capture problems in hot environments.

The micro-structure I found on the back of a Namibian “darkling” beetle (Stenocara sp.), with combined hydrophobic and hydrophilic surfaces, efficiently captures water from wind-borne fogs. This has been manufactured in plastics for use in air conditioning systems, where it recaptures water leaving the system as vapour, which can be recycled. Further, the hot water vapour no longer contributes to warming the atmosphere.

The overall aim of this research is to produce a prototype device to be employed in developing countries to collect clean water for drinking. This device will feature as many adaptations found in nature as possible, enhanced by the superior materials available in the industrial world.

The device may well contain the Namibian beetle device, since 22 different countries are subjected to desert fogs yet are short of rain. It may draw water from damp soil (rather than from more accessible puddles) in the manner of the Australian “thorny devil” lizard (Moloch horridus) or the xylem system of plants. It may filter water to make it safe for drinking as occurs in the cuticle of certain beetles, self-clean its surface as known in some plant leaves and butterfly wings, and channel and store water efficiently and safely as evident in burrowing desert frogs. Additionally, other biomimetic devices such as “moth-eye antireflectors” and “beetle heat dissipaters”, known to improve solar cell efficiency, will be incorporated where a renewable energy source is required.

Above all, the device must be resilient in the field. To achieve this, we are holding competitions at MIT (in the manner of their famous robotics competition), encouraging students to design the most practical device that may be employed in the Skeleton Coast area of Namibia. This device should showcase several new, bio-inspired technologies that are each ripe for commercialization in disparate industries.

For instance, there may even be spin offs in oil repellent surfaces, and in non-salty water collection for ships and boats at sea. Already, there have been several transatlantic visits between the NHM and MIT, and we have achieved breakthroughs such as understanding the depths to which a bird can dive based on the nanostructure of a single feather.

Most recently we have received vital support from two government ministers in South Africa, so hopefully the politics of employing our devices in Africa will keep pace with our scientific progression, and we can achieve our ultimate goal.