Nanoscience in Nature
Or
“Why Don’t Water Striders Get Wet?”
and Other Burning Questions
By Jeannie Nye
Lake Mills Middle School
Lake Mills, WI
So, Why Don’t Water Striders Get Wet?
Water striders are able to “walk on water” for a number of reasons. Striders are assisted by five things:

http://whyfiles.org/shorties/walk_on_water.html
surface area
gravitational forces
surface forces (van der Waals force)
a waxy (hydrophobic) surface on their legs
And most important -

The microhairs on their feet are
‘nano-groovy’ !
Microhairs
Nanogrooves on microhairs
Tell me more! (Click here.)
Tell me more!


Sure they are!

If, by chance, the water strider did break the water tension and take a plunge, it would not be able to dry off with a bug-sized towel. At this size, surface adhesion forces (van der Waals force) would keep the towel stuck to the water strider.

Besides, the water strider could put on a bathing suit for it`s dip; and it would never have to worry about the suit coming off when it hit the water during a high dive. First, because its so small, the water strider would float gently down because the frictional forces acting upon the water strider’s surface overcome the weak influence of gravity at this size. Also adhesion forces would keep the suit on the strider for life.

It would also be impossible for the bug to read a book by the pool, since once the pages were scaled down to bug-size, surface adhesion would keep the
pages stuck together.



http://invsee.asu.edu/nmodules/sizescalemod/unit4.htm
Surface Forces and Gravity
are Important to the Water Strider.
More information can be found on the web at http://www.exploratorium.edu/ronh/bubbles/bubbles.htm .
Activities can be found at http://www.lessonplanspage.com/ScienceExAddPenniesToFullGlassMO68.htm or
http://www.iit.edu/~smile/ph9205.html
Nano-groovy Hair
Sticky Spider Toes
These are the single hairs (setae) that make up the tuft of hair on the bottom of a jumping spider’s foot.

The oval represents the approximate size of the foot magnified to 270x.



This picture, magnified 8750x, shows the very dense nanosized setules on the underside of just one of those many seta (hairs) shown in the picture above.

http://www.primidi.com/2004/04/26.html

Tell me more!
Water strider toes help keep it dry, but this spider’s toes help make him sticky!
Spider Toes
Check out this jumping spider’s foot. Jumping spiders use nanoscale structures, too! Below thicker hairs on this spider’s leg are the nanoscale fibers that look like toes. These fibers are on the bottom of the spider`s leg, and each individual hair is covered in more hairs. These smaller hairs are called setules. Because these setules are so small they can use van derWaals force to make the spider stick to surfaces. The van der Waals force acts between individual molecules that are within a nanometer of each other (about ten thousand times smaller than the width of a human hair.) What makes the van der Waals force an interesting form of adhesion is that, unlike many glues, the surrounding environment does not affect it. The only thing that affects it is the distance between the objects (in this case, setules and the surface).

These nanofibers are small enough that the van de Waals force create a very high degree of waterproof, grease-proof, dirt-proof stickiness. When all 600,000 tips are in contact with a surface the spider can produce an adhesive force of 170 times its own weight. That`s like Spiderman clinging to the flat surface of a window on a building by his fingertips and toes only, while rescuing 170 adults who are hanging onto his back!

The total van der Waals force on the spider`s feet is very strong, but since it is due to many very small forces on each molecule the spider can lift its leg so that the nanosized setules are lifted successively, not all at once. It doesn’t need to be strong to do that.

http://www.sciencedaily.com/releases/2004/04/040426054407.htm
http://www.primidi.com/2004/04/26.html
Spider leg
Hairy toe
Setules on one hair
Lots of nano-toes!

Beetles and flies also have nanostructures that help them stick to walls, ceilings and what appear to be smooth surfaces. Tell me more!
























http://shasta.mpi-stuttgart.mpg.de/biomaterials.html

http://shasta.mpi-stuttgart.mpg.de/research/Bio-tribology.htm
Tribology is the study of friction, lubrication
and wear. When applied to living organisms this
study is called bio-tribology.

Tribology
Why do you think these nanostructures on my toes are important in biotribology?

How sticky?
As sticky as a …
http://pubs.acs.org/cen/critter/gecko.html
If their feet are that sticky, how do they pick up their feet?
http://www.cbid.gatech.edu/resources.htm

Gecko?
How Can a Gecko Lift Its Foot Off of a Surface?

These lizards uncurl their toes like a paper party favor whistle when putting their feet down and peel the toes back up as if removing a piece of tape when they step away.
http://pubs.acs.org/cen/critter/gecko1.html
How strong?
As Strong as… Silk?
The nanometer-sized biodegradable threads of spider silk are stronger, by weight, than high-tensile steel.
It is also elastic enough to stretch up to 10 times its initial length.
Toucan Beaks - Strong and Light
The exterior of the toucan beak is made up of overlapping nanosized tiles of keratin, the same protein that makes up hair, fingernails, and horn.
http://pubs.acs.org/cen/news/83/i50/8350toucan.html
http://www.nuthatch.birdnature.com/jan1897/toucan.html
The interior of the beak is a rigid foam made of a network of nanosized bony fibers connected by membranes. This allows the beak to absorb high-energy impacts.



Keratin tiles glued together
Foam-like interior made of bony fiber and drum-like membranes
http://search.eurekalert.org/e3/query.html?qt=toucan&col=ev3rel&qc=ev3rel
Nature uses Light
on the Nanoscale

What Makes Color?
http://acept.la.asu.edu/PiN/rdg/interfere/interfere.shtml
There are three possible reasons for color:

One reason is pigment. If color is due to pigment, the color never changes.
For example, a bluejay is always blue. Though pigment isn’t based on nanoscience, the next two examples of ways to create color are based on nanoscience.
Or Could Color Be Nanoscopic?

2. The colors of beetle and butterfly wings come from the scattering of light.
Light hits the nanostructures on their scales. These nanostructures are typically smaller than the wavelengths of visible light (smaller than 400 nanometers, for example).
Tell me more! (weblink)
http://pubs.acs.org/cen/critter/butterfly.html
These nanostructures
don’t just make me pretty. They also keep me clean by shedding water and dirt!
Color Can Be Iridescent, Too!


Thin films are made of nanoparticles, smaller than 400 nanometers, that
produce iridescent (rainbow-like) colors when light strikes them.

Iridescent colors change when you look at the object from different angles.
Tell me more! (weblink)
3.The third reason for color is the interference of different wavelengths of light (like oil on water).
http://acept.la.asu.edu/PiN/rdg/interfere/interfere.shtml
http://www.ptfe.gatech.edu/faculty/mohan/MSLAB-research-nanobiooptics.htm
Squid Lights
on a Nanoscale
First, it has a light-producing organ on its underside. How does it produce light? Why, it contains bacteria that produce luminescent light on the nanoscale.


Secondly, the squid has stacks of silvery nanoplatelets made of proteins behind the tissue to reflect the light downward from the squid.
The light prevents it from casting a shadow when seen from above or forming a silhouette when seen from below.

Would somebody turn on the lights, please?
http://pubs.acs.org/cen/topstory/8202/8202notw3.html
The Hawaiian bobtail squid uses a two part process to hide from predators at night.


“You Light Up My Life”
or
Bioluminescence Basics
Bioluminescence in fireflies is nanoscale. The glow is caused by the exciting of electrons by a firefly’s enzyme.

When the electrons quiet down and go back to their stable state, they give off light.

They glow to attract mates and communicate.
What’s an enzyme?
Angler fish use bioluminescent lures to attract fish.

http://www.anglerfish.info/
http://pubs.acs.org/cen/science/84/8414biolum.html
A “Blue Light Special”
Tiny crustaceans, Ostracods, also known as "seed shrimp" or "sea fireflies," also use this enzyme to produce bioluminescence in courtship. The males produce blue dots in the water, which are used to attract mates.

http://www.pisces-conservation.com/index.html?softost.html$softebookmenu.html
A close-up using a scanning electron microscope
http://pubs.acs.org/cen/science/84/8414biolum.html
Jellyfish Lights
A jellyfish-type invertebrate, called a siphonophore, uses red bioluminescent lures created at the nanoscale to attract prey.
Doesn’t it seem odd that it would use red light since red isn’t easily visible underwater?
http://www.coml.org/medres/high2005/highlightimages.htm
Click here for a weblink to a video and lesson on bioluminescent deep sea organisms.

Bioluminescence Lesson
There’s an interesting, though high level, video clip at http://pubs.acs.org/cen/multimedia/84/biolum/Biolum_content.html
NSTA provides a lesson on bioluminescence. It can be found at http://www.nsta.org/main/news/stories/science_scope.php?category_ID=87&news_story_ID=52197

http://www.mbayaq.org/efc/living_species/default.asp?hOri=0&hab=9&inhab=182

Hippo Sweat is Nanoscience?
Hippo sweat contains compounds that absorb light in the range of 200 – 600 nanometers. This compound protects the hippo’s skin like sunscreen.

One of the compounds in hippo sweat, hipposudoric acid, inhibits bacterial growth and is hydrophilic, too. Can you think of ways the hippo benefits from these properties?
http://pubs.acs.org/cen/news/8222/8222notw9.html
http://www.pbs.org/kratts/world/africa/hippo/index.html
Get Ready, Get Set,
Drink!
Imagine you’re a very thirsty tiny beetle in a desert. How can you get a drink?

The Namib desert beetle in the deserts of southwest Africa has a novel idea.

First it must collect drinking water using its wings, which are waxed and covered with raised unwaxed nanobumps. The bumps attract
water (hydrophilic). When enough water collects it rolls down the waxy areas, which repel water (hydrophobic), into the beetle’s mouth.

Click here for more information!



http://biomechanics.bio.uci.edu/_html/nh_biomech/namib/beetle.htm
http://www.newscientist.com/article.ns?id=dn1508
A closeup of the nanobumps on a beetle’s back.
But How Does the Water
Get to Its Mouth?
Six times a year when the fog blows in from the Atlantic the Namib beetle turns a 45 degree angle to the wind so that the droplets of water from the fog stick to the unwaxed bumps on its back. This water builds up before rolling down the water-repelling waxed troughs on the beetle`s back and into its mouth.

Speaking of Water…
Let’s Look at Snowflakes!
Have you ever looked closely at a snowflake



and wondered why they’re all different?
For more information click on the following link: http://www.its.caltech.edu/~atomic/snowcrystals/primer/primer.htm
It’s Because They’re Nano-Flakes!
They build up on the nanoscale, one molecules at a time. Their size and shape is determined by the altitude and air pressure where they are formed.




Use the same bottom up construction to make your own snowflakes by clicking on this web link: http://profhorn.meteor.wisc.edu/wxwise/snowflake/makesnow.html

Nanoscience Is Everywhere
in Nature
Living cells have been using their own nanoscale devices to create structures one atom or molecule at a time for millions of years.

To be specific, DNA is copied, proteins are formed, and complex hormones are manufactured by cellular devices far more complex than the most advanced manufacturing processes we have today.
http://dallas.bizjournals.com/dallas/stories/2001/09/10/focus2.html?page=3
Click here for an example!
“Mighty Oaks
from Little Acorns Grow”
For example, an acorn uses the energy within it to read nanoscale DNA. The DNA is coded to sprout roots and leaves. These structures can gather more energy from the soil and the sun. The DNA tells the acorn to rearrange the atoms in soil, air and water to produce an oak tree, a material far more complex than today`s material science can produce.

Mother Nature
Mankind has always found inspiration in
Mother Nature. Today developing
technologies allow us to probe and better understand the nanoscience of Mother Nature.