Nanotennis

By Simon Shapiro

Nanotechnology deals with particles ranging in size from 1 to 100 nanometers. A nanometer is one millionth of a meter. That's very small: a newspaper page is about 100,000 nanometers thick. Atoms are about .1 to .5 nanometers in diameter, so nanotechnology works at a molecular level.

Materials start behaving differently at nano scale and scientists are learning about this behaviour and finding uses for nano materials. One of the success stories has been graphene and carbon nanotubes.

Graphene
Image by AlexanderAlUS

 Graphene consists of a lattice of carbon atoms in a hexagonal pattern. It's a sheet of carbon one atom thick. And it's the strongest material ever discovered – 200 times stronger than steel, but also very light and flexible.

Carbon Nanotube
By Arnero - Own work, Public Domain

Graphene can be formed into a cylindrical shape, which is call a nanotube. It's light, strong and stiff.

 So what does nanotechnology have to do with tennis? Would you believe tiny tennis players hitting electrons across a 1 nanometer high net? No, me neither.

In the early 1970s an aeronautical engineer by the name of Howard Head, revolutionized tennis by inventing a racket with a much bigger face. It was a huge improvement over existing rackets especially for average players. Head did this by making the frame out of aluminum, instead of wood, which wasn't strong enough for larger rackets. (This was Head's second sports revolution: 25 years earlier he had developed plywood/aluminum/steel/plastic skis which blew away the existing solid hickory ones. You can read about this story in my book Faster, Higher, Smarter.)

Head's idea of a larger racket face is still the dominant design, but technologists have been working away to improve the materials used. And the most advanced rackets today all use graphene sheets or nanotubes to make portions of the racket lighter, stronger and more rigid.

Silica (silicon dioxide) is another nanotechnology material used in tennis rackets. Silica nanoparticles are used to fill the gaps in other materials, for example between nanotubes. The silica adds stability and strength, without adding much weight.

Clay Nanoparticles
Silicon atom at the centre and four
oxygen atoms at the vertices

Still with tennis, balls use clay nanoparticles on the inside membrane. These silicon oxide particles are tetrahedral shaped molecules which form a barrier to gas. No gas leaking out gives the ball a longer life.

Fullerenes (or Buckminsterfullerenes, or just "Buckyballs") are carbon molecules made up of 60 carbon atoms linked into pentagons and hexagons, forming a structure that looks exactly like a soccer ball. It also looks like a geodesic dome. (The American architect, Buckminster Fuller, popularized the geodesic dome, earning him the nano-homage).  While we're on the subject of appropriate names, one of the three Nobel laureates for discovering Fullerenes was Richard Smalley!

Soccer ball 
By Pumbaa80 (Self-published work
by Pumbaa80) via Wikimedia Commons

Buckminsterfullerene
By Mstroeck at English Wikipedia

Buckyballs are also used in tennis rackets, to make them lighter and more resistant to twisting.

Nanotechnology is used in lots of other sports equipment.

• Golf clubs: carbon nanotubes are used for strength and lightness. Buckyballs are used for flexibility.
• Fishing rods: use silica nanoparticles to fill spaces between carbon fibres, strengthening the rod without increasing the weight. 
• Kayaking: carbon nanotubes are used to enhance resistance to abrasion and cracks; nanoclay is used to reduce weight and resistance, making it easier to paddle.
• Archery: carbon nanotubes reduce vibration in arrows.
• Bowling: buckyballs reduce chipping and cracking on bowling balls.
• Cycling: graphene and carbon nanotubes are used to build very strong and light bicycle frames. 

Nanotechnology is really important in other industries, of course: electronics, pharmaceuticals, textiles, food ... More to come in future blogs.

Bernoulli Is Not Enough

By Simon Shapiro

Probably all of us science geeks think we know how aeroplanes fly. It’s thanks to the Bernoulli Principle, which says that faster flowing air exerts less pressure than slower air. Aeroplane wings are designed with flat bottoms and rounded tops. Air has to flow more quickly around the longer top surface than the shorter bottom surface. That gives us higher pressure below the wing and lower pressure above the wing.

This diagram is from my book, Faster, Higher, Smarter: Bright Ideas that Transformed Sports. (More information here; available from Amazon, Indigo, etc.)

So, the upward Bernoulli force overcomes the downward force of gravity, and the aeroplane can fly.

But there's a problem:

Think about a plane doing aerobatics. A pilot will happily flip her plane upside down and can fly that way indefinitely (at least until the plane runs out of fuel). But in the upside down configuration the Bernoulli force is directed downwards, just like gravity. So with both forces acting downward, how come the aeroplane doesn’t fall like a stone? Worse than that, like a stone with an extra downward force?

The answer is that there’s another factor, usually overlooked. And that’s the Angle of Attack. Aeroplanes don’t usually fly with the bottom of the wing parallel to the ground. They usually fly with the leading edge tilted up. That tilt angle is called the Angle of Attack.

In this configuration the wing pushes against the air and (thank you, Sir Isaac) experiences a normal (perpendicular to the surface) reaction  of wind resistance. That’s shown as the red arrow in the diagram above. The force shown by the red arrow is the same as two forces – a vertical one (shown by the green arrow) and a horizontal one (shown by the tiny blue arrow). That vertical “green arrow” force counteracts gravity, and is what keeps an upside-down aeroplane in the air.

In fact the Bernoulli effect alone isn’t strong enough to keep a heavy modern jet plane up. The Angle of Attack is critical even when the plane is flying rightside up.