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Play It Backwards

Posted on February 22 2013 by secret santa

"Using a “time-reversal” technique, the team has discovered how to transmit power, sound or images to a “nonlinear object” without knowing the object’s exact location or affecting objects around it. “That’s the magic of time reversal,” says Steven Anlage, "when you reverse the waveform’s direction in space and time, it follows the same path it took coming out and finds its way exactly back to the source.” Imagine a cell phone charger that recharges your phone remotely without even knowing where it is; a device that targets and destroys tumors; or a security field that can disable electronics, even a listening device hiding in a prosthetic.

What differentiates this research from other time-reversal projects, such as underwater communication, is that it focuses on nonlinear objects such as a cellphone, diode or even a rusty piece of metal - when a waveform bounces off them, the frequency changes. Most components electrical engineers work with are linear—capacitors, wire, antennas—because they do not change the frequency. With nonlinear objects, however, when the altered, nonlinear frequency is recorded, time-reversed and retransmitted, it creates a private communication channel because other objects cannot “understand” the signal. “Time reversal has been around for 10 to 20 years but it requires some pretty sophisticated technology to make it work,” Anlage says. “Technology is now catching up."

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