15-year-old girl invents flashlight powered by the heat of your hand

The flashlight she built employ an aluminum tube slipped inside of a PVC pipe. The pipe was cut away in a certain area so the person's hand would come into contact with the built-in Peltier tiles. The flashlight worked, but due to the temperature reliance of Peltier tiles, the flashlights worked better in colder temperatures (tested at 41 degrees Fahrenheit). The flashlight still worked in warmer temperatures (50 degrees, for instance), but the colder the surrounding temperature, the more the hand's body heat can help the Peltier generate electricity. The flashlight maintained a sufficient level of light for over 20 minutes, definitely enough time to find the candles in the dark when the power goes out. In total, Makosinski built the flashlight for $26, which is definitely a fine price for a flashlight that doesn't require batteries, but she believes if mass produced, it could become even cheaper. If Makosinski wins the Science Fair in September, she'll certainly be able to make a lot of flashlights.