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Teenager invents flashlight powered by the warmth of your hand

LED light
Makosinski's palm-powered flashlight.Ann Makosinski / YouTube

A 15-year-old girl has invented a flashlight that produces a usable amount of light just by using the heat from your hand. And if the judges at the Google Science Fair like it, she may be on her way to the grand prize.

Ann Makosinski of Canada entered another Science Fair last year with a flashlight that used kinetic energy to power its LEDs, and this year she wanted to try making one that worked via the thermoelectric effect. That's when a small amount of electricity can be harvested as electrons flow between the cool and hot sides of a material.

"I’m sure we’ve all had that annoying experience when we desperately need a flashlight, we find one, and the batteries are out," she said in an email interview with NBC News. "Imagine how much money we would save and the amount of toxins leached into the soil etc reduced if we didn’t use any batteries in flashlights!"

The question was whether enough electricity could actually be made just from holding the flashlight — humans generate a lot of heat (and therefore, potentially electricity), but Ann didn't have the whole body to work with, just one average palm.

LED light
Makosinski's palm-powered flashlight.Ann Makosinski / YouTube

First, she measured how much electricity could be generated from the heat of a palm — about 57 milliwatts — and how much she needed to light the LED — about half a milliwatt.

Next, she got the parts together: several Peltier tiles ("I got them surplus off Ebay," she said), which when warm on one side and cool on the other could generate electricity, and a few other bits necessary to make the current usable by a normal LED.

Finally, she mounted the tiles and circuitry onto a hollow aluminum tube; air inside the tube would cool the Peltier tiles, while the warmth of a hand would heat the other side. And with a little tweaking of voltages and other components, it worked!

The light generated is modest, but enough to find your keys or light the page of a book. It worked for around half an hour in her tests at an ambient temperature of about 50 degrees Fahrenheit, but would last longer or shorter depending on temperature differences.

"The flashlight I have made is more of a prototype then a final product, but the components in my device are quite strong," Ann wrote. "Of course, if it was to be used and manufactured, I would try to seal off the electronic components in some sort of casing so that it wouldn’t get heavily exposed to the elements (example water), and therefore last longer."

She'll be traveling from Victoria, British Columbia to Mountain View, Calif. to visit Google headquarters in September for the final judging event. There, the 15 finalists will present their projects personally to a panel of leading experts and scientists. The competition is fierce, but the prize, which includes a $50,000 scholarship, tutelage at one of several organizations, and a trip to Galapagos, is definitely worth fighting for.

Ann seems ready. "It’s an absolutely amazing experience, and I’m still shocked that my project made it this far, and I feel very blessed to have this experience. But it’s definitely a big shock for me, and an honor to be representing Canada!"

Devin Coldewey is a contributing writer for NBC News Digital. His personal website is