“Nanotubes assemblies of various types are black and highly conductive,” said Dr. Mikhail Kozlov, a research scientist and the study’s lead author. “Their dark, conductive surface can be effectively heated with laser light or electricity to induce variations in the pressure of the air around the nanotubes — which we perceive as sound. It’s called the photo- or thermo-acoustic effect, and it’s the same principle Alexander Graham Bell used to produce sound on the first telephone.”
With laser excitation, no electrical contact with the nanotube speaker is required, making the speakers wireless.
“Speakers made with carbon nanotube sheets are extremely thin, light and almost transparent,” Kozlov said. “They have no moving parts and can be attached to any surface, which makes the surface acoustically active. They can be concealed in television and computer screens, apartment walls, or in the windows of buildings and cars. The almost invisible strands form films that can ‘talk.’”
In addition to filling a room with sound from invisible speakers, nanotube speakers could easily cancel sound from the noisiest neighbor or dim the roar of traffic rushing past a neighborhood, using the same principles as current sound-canceling technologies.
“The sound generation by nanotube sheets can help to achieve this effect on very large scales,” Kozlov said.
Future Mars outposts or colonies may seem more distant than ever with NASA's exploration plans in flux, but the rocket technology that could someday propel a human mission to the red planet in as little as 40 days may already exist. A company founded by former NASA astronaut Franklin Chang-Diaz has been developing a new rocket engine that draws upon electric power and magnetic fields to channel superheated plasma out the back. That stream of plasma generates steady, efficient thrust that uses low amounts of propellant and builds up speed over time. "People have known for a long time, even back in the '50s, that electric propulsion would be needed for serious exploration of Mars," said Tim Glover, director of development at the Ad Astra Rocket Company.
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