By Eric Rosenthal
After air travel security banned bottled water and baby formula, I began wondering why they didn’t use a device to determine the contents of liquids. If a liquid was detected to be safe, security could allow it on the plane.
Spectrometers can identify the chemical makeup of a material by shining light on it and analyzing the precise mix of colors that bounce back. These devices are usually very expensive, but I’ve designed a simple and inexpensive one that can identify liquids. You can also adapt it to determine the color of a swatch of paper or cloth or to identify a gem or semiprecious stone.
I spent less than $100 on this project and it took just a few days to design, fabricate, and test the hardware, plus another two days to write and debug the source code. Collecting the liquids and building the database took one evening, and it was fun!