From PhysOrg:
When Dr. Leonard “Bones” McCoy needs to diagnose an ill member of the Starship Enterprise, he simply points his tricorder device at their body and it identifies their malady without probing or prodding. Similarly, when Capt. Kirk beams down to an alien world, his tricorder quickly analyzes if the atmosphere is safe to breathe. Now Stanford electrical engineers have taken the latest step toward developing such a device through experiments detailed in Applied Physics Letters and presented at the International Ultrasonics Symposium in Taipei, Taiwan. The work, led by Assistant Professor Amin Arbabian and Research Professor Pierre Khuri-Yakub, grows out of research designed to detect buried plastic explosives, but the researchers said the technology could also provide a new way to detect early stage cancers. The careful manipulation of two scientific principles drives both the military and medical applications of the Stanford work.
First, all materials expand and contract when stimulated with electromagnetic energy, such as light or microwaves. Second, this expansion and contraction produces ultrasound waves that travel to the surface and can be detected remotely. The basic principle of this interaction was first revealed in 1880 when Alexander Graham Bell was experimenting with wireless transmission of sound via light beams. Bell used light to make sound emanate from a receiver made of carbon black, which replicated a musical tone. The Stanford engineers built on the principles demonstrated in Bell's experiment to develop a device to “hear” hidden objects.
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