Engineering exercises from Science Buddies

Key Concept Nanotechnology Material Strength Engineering Introduction Have you ever seen superhero movies where superheroes rely on super strong materials, such as Wolverine’s King Kong claws, Captain America’s vibrating shield or Iron Man’s armor? Scientists and engineers in comic books are dedicated to creating fictitious materials to help superheroes win, while real-world scientists and engineers are actually already creating super-strong materials with multiple uses-from improved bulletproof vests to stronger Ropes, then lighter bicycles, better spaceships. In this activity, you will explore how the shape of the molecules in a material can significantly affect its strength, using only paper. Who knows, maybe this will put you on the road of designing your own super powers! Background Nanotechnology is the science of studying materials on the "nano" scale or the scale of individual atoms and molecules. How small is the nanoscale? A nanometer is one billionth of a meter. A typical human hair is about 100,000 nanometers wide-so one nanometer is really small! The structure of nanoscale materials can significantly change the way they behave. For example, a pencil contains graphite, which is composed of carbon atoms arranged in thin slices and can be easily slid around. It is easy to write with a pencil because the graphite flakes are easy to wipe off on the paper. However, carbon atoms also constitute some of the strongest materials in the world-diamonds! In diamonds, carbon atoms are packed tightly together, making them hard enough to cut steel. Scientists are working on another super strong version of carbon atoms called carbon nanotubes, which consist of sheets of carbon atoms rolled into tiny cylinders! Although this makes individual carbon nanotubes very strong, mass production of carbon nanotubes is still a challenge. In this activity, you will compare the strength of paper stacked into sheets and rolled into tubes to simulate the difference between flake graphite and carbon nanotubes. Material

Observations and results Are rolled paper stronger than stacked paper? You should have discovered that paper rolled into a tube is much stronger than paper that is simply stacked together, so it can bear the weight of more coins. Like the carbon atom flakes in pencil graphite, the stacked paper flakes are "flaky"-they can easily slide on top of each other, which makes them very fragile and unable to withstand a lot of weight. When a piece of paper is rolled into a tube, it becomes stronger, even though it is still the same piece of paper. This is similar to how carbon atoms become stronger when they form tiny cylinders in carbon nanotubes. Please note that in this activity, you simulate the difference between graphite sheets and carbon nanotubes by comparing paper sheets with paper tubes. Although compared to the "macro scale" (or the scale of everyday objects we are used to), physics behaves differently on the nanoscale of a single atom, but the general principle remains the same-you can completely change the material by changing the strength of the material The strength of its shape. More exploration and exploration of nanotechnology: ways to fold, roll and stack super-strong materials, from Science Buddies Nanotechnology, Chris Woodford at Explain That Stuff! Nanotechnology, Big Things from a Tiny World (pdf), from National Nanotechnology Coordination Office Science Activities for All Ages!, from Science Buddies

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