Today was fun...the College of Engineering hosted "Engineering Expo." The entire engineering campus was decked out with displays from a wide variety of students, clubs, and departments, and flooded with families. I was involved with three displays:

1. Making carbon nanotube models out of balloons
Carbon nanotubes are cylinders of carbon atoms arranged in 6-sided rings (they look a lot like nanoscale chicken wire). They are only a few billionths of a meter across, but can be a whopping few millionths of a meter in length (about the width of a human hair!). They are exciting to study because they are stronger than steel nanowires (and thus can be mixed into plastics to make them stronger), and if the carbon atoms are arranged correctly, they conduct electricity better than copper wire (so they could theoretically be used to make nano-computers). Yesterday, several people made a giant balloon nanotube model, about as tall as a house (at least as tall as an average room). It was fun!

2. Teaching kids how blood pressure sensors and Doppler ultrasound machines work
The ultrasound machine was my favorite. It's a small microphone/speaker, about the size of a small flashlight. It works based on the "Doppler effect," i.e. that when sound bounces off of a moving object, its pitch changes. When the sound from the ultrasound machine bounces off of moving blood cells, the machine can tell whether the cells are coming toward the microphone (i.e. the pitch is higher) or away from it (i.e. the pitch is lower). It has a speaker on it, so when you put it against an artery, you can hear the blood rushing through it. The younger kids especially liked it ("Dad! Listen! That's the blood in my arm!").

3. Detecting salt with gold
When gold particles are very small (i.e. nanoscale), they aren't yellow anymore--their color changes depending on how small the particles are (very small=blue, extremely small=red). We used a solution of red nano-sized gold particles (it looked like cranberry juice). When we added salt water, it made the gold particles stick together, which made them look blue. It was fun--we had people test Gatorade, pickle juice, and flavored water to see which one had the most salt. Pickle juice turned the solution dark blue, but flavored water didn't noticeably change it.

In summary, today was great. I would like to help out with educational events more often.