Super Soaker Inventor Invents New Thermoelectric Generator

Lonnie Johnson has moved on from high-powered squirt guns to a chip that converts heat from the sun--or anything else--into electricity

4 min read

20 March 2008—His best-known invention, a high-powered water pistol, is a fun solution to a hot day in the sun, but to Lonnie Johnson, the potential of solar energy is no laughing matter. ”The sun is the only source that will be able to meet future terawatt levels of power demand, as more and more countries become industrialized and seek to improve their standard of living,” says Johnson, who is also the founder of Johnson Electro Mechanical Systems, in Atlanta. Harnessing the sun’s energy, of course, is easier said than done. But Johnson has developed a new kind of device that converts heat into electric current. He says it has the potential to be the best-ever method of converting solar energy into a form that we can use.

Among the potential applications are at utility-scale solar thermal farms and for plug-in hybrid vehicles, in which the device would use waste heat from the car’s internal combustion engine to help power the car’s electric motor. Johnson even envisions a day when miniaturized versions will power consumer electronics. Imagine your laptop producing power from its own waste heat, your cellphone being charged as you hold the handset against your face, or an implantable medical device exploiting the difference in temperature between, say, your chest cavity and the skin on your arm.

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How the First Transistor Worked

Even its inventors didn’t fully understand the point-contact transistor

12 min read
A phot of an outstretched hand with several transistors in the palm of it.

A 1955 AT&T publicity photo shows [in palm, from left] a phototransistor, a junction transistor, and a point-contact transistor.

AT&T ARCHIVES AND HISTORY CENTER
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The vacuum-tube triode wasn’t quite 20 years old when physicists began trying to create its successor, and the stakes were huge. Not only had the triode made long-distance telephony and movie sound possible, it was driving the entire enterprise of commercial radio, an industry worth more than a billion dollars in 1929. But vacuum tubes were power-hungry and fragile. If a more rugged, reliable, and efficient alternative to the triode could be found, the rewards would be immense.

The goal was a three-terminal device made out of semiconductors that would accept a low-current signal into an input terminal and use it to control the flow of a larger current flowing between two other terminals, thereby amplifying the original signal. The underlying principle of such a device would be something called the field effect—the ability of electric fields to modulate the electrical conductivity of semiconductor materials. The field effect was already well known in those days, thanks to diodes and related research on semiconductors.

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