Lab: Learning From Nature’s Water Harvester
Nature has been doing its thing for years – and estimated four billion years, actually.
After all this time, organisms that managed to survive have adapted to solve the issues of
what they need to survive. They have perfected techniques that we as humans are still
searching after. From self-cleaning to shelter to efficient mechanisms, nature holds the
keys to the solutions of many current problems.
Biomimicry is being used by engineers and scientists in two main directions: taking
problems and looking for answers in nature, or looking at nature’s principles and finding
applications for them. In any case, new ideas and technologies can then be modeled after
nature, seeking simplicity and efficiency at the same time.
In this lab, we will explore three examples of biomimicry, namely the surface character
of the Namib desert beetle, the attachment mechanism of burrs, and the design of the
kingfisher’s beak for traveling through different mediums.
Inspiration is our first requirement. Then there is thirst. Without air, the human body
expires in minutes. Without water, it’s a matter of days before the body succumbs. Yet
nearly 1 billion people worldwide live under the pall of tainted or unreliable water
sources.
Tejas Sundaresan and Jaehyeong Lee, NCSSM juniors, have committed themselves to
solving this water problem. They conceived of a technology that would extract water
vapor from the air and condense it for clean drinking water. They call it “amphipathic
films for water collection,” and their idea took first prize at the 2012 Toshiba
ExploraVision competition, the world’s largest K–12 science competition, which
challenges students to envision new technologies that could make the future healthier and
safer.
Lee and Sundaresan’s amphipathic film is inspired by the stenocara beetle of the Namib
Desert, which extracts water vapor from the atmosphere via hydrophilic nodules and
hydrophobic channels. The young inventors want to apply this natural technology on a
macroscopic scale.
Part 1: Namib Desert Beetle
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The Namib Dessert Beetle drinks its
water with a very interesting mechanism.
It has hydrophobic ridges and bumps on
its back which help direct water.
Hydrophobic (“water hating”) means that the surface will repel water. When water lands
on these bumps, the water will flow away from the hydrophobic surfaces and into
hydrophilic (“water loving”) grooves in the surface. Thus, the beetle collects water that
condenses on its shell and concentrates it into one point from which it flows into its
mouth.
In this lab, we will try to mimic this effect making our own hydrophobic/hydrophilic
surface. We will use foam board as our hydrophilic surface, and cover parts of it with
crayon, synthesizing a hydrophobic surface. The goal of this lab is to direct water using a
hydrophobic/hydrophilic surface to one point. You are to design a pattern such that when
water is sprayed on the surface, the water flows into one concentrated point.
Part 2: Procedure
1. Design a pattern that would create a path for water to flow into a cup.
2. Cut out a 10 in x 10 in piece of foam board
3. Using crayon or some other sort of waxy substance, copy your pattern onto the
poster board.
4. Put the piece of poster board on a 45 degree incline with the pattern facing up so
that the water can be collected in the cup.
5. Using a spray bottle, spray the surface of the foam board ___ times and collect the
run-off water. (Decide the number of trials needed based on size of spray. Keep
the number the same each time.)
6. Using a graduated cylinder, measure the amount of water collected.
7. Repeat the collect method 3 times and average your data.
Example: A simple, directed hydrophobic coloring (left); after squirting the surface,
water directed toward the middle to flow down, and collected into droplets on the
hydrophobic surfaces to roll down (right)
Part II
1. Go to web and look at leaves or other biological surfaces and redesign your
pattern.
2. Think about the width of the hydrophobic surface and the space between the
hydrophobic surfaces you make. Those on the beetle are very small.
3. Based on your first set of trial, design a new pattern that you think will collect
even more water. Test your new pattern following the procedure as before.
Discussion Questions:
In this lab we used spray because it is quick and easy. In the desert the beetle collect
condensation. How could you design a better method to test your pattern for collection in
the desert?
What practical applications are there for this device?
What makes a successful pattern?
What other hydrophilic and hydrophobic materials are there? How could they be applied?
References:
Student designer of the lab – Christie Jiang and Yu Wang
http://www.asknature.org/strategy/dc2127c6d0008a6c7748e4e4474e7aa1 - Ask Nature Namib Desert Beetle Biomimicry Strategy Page – Idea for the project
Sundaresan, T., Lee, J. 2012 “Amphipathic Films for Water Collection” Exploravision –
Previous Example of Project
http://www.rexresearch.com/qinetiq/qinetiq.htm - Dr Cohen - Dew Collector
Lawrence, C., Parker, A., 2002, Hydrophobic and Hydrophilic Surface, for Promoting
Droplet Formation
Sites
http://dev.nsta.org/evwebs/1987v/whatsnext.html - Exploravision Website
http://dev.nsta.org/evwebs/1987v/prototype.html - Exploravision Prototype
http://www.youtube.com/watch?feature=player_embedded&v=n2ix0fDFTdc - Namib
Desert Beetle