Under the right conditions, tiny synthetic hairs will twist together to form intricate braids. Joanna Aizenberg, professor of materials science, chemistry and chemical biology and Radcliffe professor at Harvard University, shows us what the nano-sized knots look like and what they might be good for.
Grade Level: 6th – 8th grade
Subject Matter: Physical Science
National Standards: NS.5-8.1, NS.5-8.2
Nanotechnology is the study of what happens when things get very, very small – only a few atoms in size. The word “nanometer” means one billionth of a meter, perhaps five or six atoms long. At the nanoscale, materials can have very different physical or chemical properties, even though they are the same. In particular, super thin films of material, only a few nanometers thick, can cause interference within light reflecting off them, resulting in beautiful displays of colors.
In this activity, students will observe some of the effects that result from creating a thin layer of material several nanometers thick. They also will learn about thin film interference and how it applies to bubbles and oil spots on roads.
Clear nail polish
Black construction paper, enough for each student
Rectangular aluminum pan, one for each student
Nanotechnology: the study and manipulation of materials on the nanoscale (about 1 to 100 nanometers).
Nanometer: a unit of measurement that equals one billionth of a meter.
Reflect: what light does when it bounces off an object or surface.
Constructive interference: what happens when certain colors of light build up to create more intense colors than before.
Destructive interference – what happens when certain colors of light cancel each other out.
What To Do
Begin the lesson by having students watch the Science Friday Video “Nano Hairs Twist into Tiny Dreadlocks.” Ask students to describe the smallest thing they can imagine, and begin a discussion that will lead to the introduction of conditions at the nanoscale. Tell students that they will be making a layer of material so thin it will change the way light behaves when passing through it.
Hand out a sheet of black construction paper and an aluminum pan to each student. If necessary, have students cut the paper so that it will fit neatly on the bottom of the pan.
Have students pour enough water into the pan to cover the paper by about one half an inch. If the paper starts to float, have students push it back down.
Have students examine a bottle of clear nail polish. Ask students to hold the bottle up to the light. What color is the nail polish? Can they see any colors in the nail polish by looking through the bottle at different angles?
Tell students that a drop of nail polish will be dripped into the water. Do they think that there will be any difference in the clear color of the nail polish? Have students use the brush from the bottle to drip one drop of nail polish onto the surface of the water. What happens to the nail polish? Have students explain why the drop is spreading into a thin film.
After 30 seconds, have students gently remove the paper by holding on to the corners and pulling the paper straight out, so that the film adheres to the paper while the water runs off to the side. Carefully place the black paper on newspaper to dry.
Have students observe the thin film on the paper from different angles. What do they notice? Does the layer of film look thin or thick? Why did the clear nail polish suddenly exhibit these colorful patterns?
Optional: Have students make more film prints. Compare prints to observe any differences or similarities. Try changing other variables such as nail polish color or the color of construction paper.
Once the prints are completely dry, give students the option of keeping and framing their prints.
Nanotechnology is the study and manipulation of materials on a very, very small scale. A nanometer is a unit of measurement that equals one billionth of a meter. A DNA molecule is about 2.5 nanometers wide. A human hair, in comparison, is considered “big” at 80,000 nanometers. Certain materials under 100 nanometers (often referred as the nanoscale) have been observed to demonstrate changes in properties or to exhibit new properties. For example, pencil lead is a form of carbon that is soft and therefore easy to use for writing. However, scientists have observed a form of nanoscale carbon, called a carbon nanotube, that is stronger than steel!
In this experiment, when the clear nail polish was dripped onto the surface of water, it spread out into a very thin layer or film, only a few hundred nanometers thick, with some parts being thicker than others. When light waves strike thin films like these something strange happens: colorful patterns appear on the surface. This happens because white light is actually a combination of many different colors, a spectrum of colors. When light strikes the surface of the film, some of it is reflected and some of it goes through the surface, bounces back off the water and re-emerges out through the top of the film. Depending on the thickness of the film, the light waves will either cancel each other out (destructive interference) or reinforce each other to make brighter bands of color (constructive interference). This is the same process that creates rainbow-like colors in bubbles and in oil spots on wet roads or driveways.
Topics for Science Class Discussion
What would happen if more than one drop of nail polish was used? Or if you observed your paper under different types of lights?
How can thin film interference be useful to scientists?
Explain how the colored pattern can be compared to a topographic contour map of light wavelengths.
What are the benefits of studying nanotechnology? Are there any disadvantages or controversies surrounding nanotechnology?
Can you find at home a product that is made using nanotechnology?
Extended Activities and Links
Bend a large paper clip or pipe cleaner to make a big loop. Dip the loop into a bowl of soapy water and hold it above the bowl. What happens to the rainbow colors as the soap sinks down to the bottom of the loop?
Ask students to make a graph illustrating materials that range in size from the nanoworld to the microworld. Have students draw sketches or paste pictures from magazines that match each material in the graph.
Assign students to research nanotech materials that are used today and to predict their own nanotech device for the future. Have a “Nanotech Fair” and let students present their nanotech device.
Learn about light interference while playing with bubbles!
Explore how the same principle applies to the iridescence of butterfly wings.
Explore the possibilities of nanotechnology with fun online games and puzzles.
This lesson plan was created by the New York Hall of Science in collaboration with Science Friday as part of Teachers Talking Science, an online resource for teachers, homeschoolers, and parents to produce free materials based on very popular SciFri Videos to help in the classroom or around the kitchen table.
The New York Hall of Science is a science museum located in the New York City borough of Queens. NYSCI is New York City's only hands-on science and technology center, with more than 400 hands-on exhibits explore biology, chemistry, and physics.