{"id":197,"date":"2010-08-16T10:21:01","date_gmt":"2010-08-16T00:21:01","guid":{"rendered":"https:\/\/scienceillustrated.com.au\/blog\/?p=197"},"modified":"2010-08-17T14:37:39","modified_gmt":"2010-08-17T04:37:39","slug":"worlds-smallest-radio-may-cure-blindness-detect-harmful-chemicals","status":"publish","type":"post","link":"https:\/\/scienceillustrated.com.au\/blog\/features\/worlds-smallest-radio-may-cure-blindness-detect-harmful-chemicals\/","title":{"rendered":"World’s smallest radio may cure blindness, detect harmful chemicals"},"content":{"rendered":"
\"\"<\/a><\/p>\n

Illustration: Claus Lunau<\/p>\n<\/div>\n

Nanoradios work by using physical vibrations. They won’t change how we listen to music, but they could have a significant impact on the world of medicine.<\/strong><\/p>\n

<\/strong>When the radio was invented in the 1890s, no one dreamed that 120 years later there would be a version small enough to fit inside a living cell. The first “nanoradio”\u009d was built at the University of California at Berkeley in the US in 2007, when physicists at the Centre of Integrated Nanomechanical Systems (COINS) realised that the mechanical properties of a single carbon nanotube meant that it could function as a radio.<\/p>\n

Although nanoradios don’t have tremendous potential for consumer gadgets \u2014 who needs a music player smaller than the width of a human hair? \u2014 the technology might have profound medical and environmental applications.<\/p>\n

It could restore vision, for example. For some types of blindness, doctors can bring back sight by electrically stimulating specific areas of the brain. In current therapies, wires connect electrodes implanted in the brain to an external power source. But the wires can cause infections. In 10 years, an array of implanted nanoradios could be stimulating the brain wirelessly, says COINS physicist Alex Zettl, whose team invented the tiny radio.<\/p>\n

Zettl also predicts that the radios, coupled with similarly small transmitters in development at COINS, will one day be built into remote-controlled nanodevices that communicate with each other. The nanoradios and transmitters could be used to monitor thermal or chemical conditions, including the air quality in a city or the toxic chemicals in a factory, without the tangle of wires required by existing systems. “But the real advantage in going nano,”\u009d Zettl says, “is that the power requirements are much smaller.”\u009d In environmental applications, a smaller power source means lower costs. In medicine, it means that a single living cell could power sensors inside the body.<\/p>\n

Four-part harmony<\/strong>
\nFor all their futuristic practical applications, the world’s smallest radios play music as well. One of the first songs Zettl and his colleagues played to prove that their nanoradio worked was “Good Vibrations”\u009d by the Beach Boys. It’s a bit of lab humour \u2014 vibrations are the secret behind nanoradios.<\/p>\n


\nA typical radio has four main components: an antenna, a tuner, an amplifier and a demodulator. The antenna picks up radio signals; information like a voice or song is encoded into these signals by modulating the frequencies (FM radio) or amplitudes (AM radio) of the so-called carrier waves. When you change the dial on your car radio to tune in a specific station, the tuner is detecting a specific frequency of the carrier wave. Once that is accomplished, the radio’s amplifier increases the strength of the signal, making the details more apparent. The demodulator then decodes the information.<\/p>\n

The carbon nanotube in Zettl’s radio, which is able to detect both AM and FM signals, takes on all four of these roles. To do so, a nanotube typically less than 0.005 of a millimetre long (and one millionth as thin as that) is anchored to a metal electrode that functions as a negative pole. A short distance away from it sits a positively charged metal electrode. Connecting a battery between the electrodes shoots current through the conductive nanotube to its tip. But the electrons won’t make the jump to the positively charged electrode about a micrometre away unless the conditions are just right. Instead they stop at the tip, creating an electric field. If the nanotube is exposed to an electromagnetic radio wave in a specific wavelength, the tip will begin to vibrate up and down rapidly.<\/p>\n

Here, the nanotube is acting as an antenna. Changing the length of the nanotube tunes the nanoradio \u2014 the shorter the tube, the higher the frequency at which it will vibrate. As the nanotube antenna vibrates, the distance between the tip and the positive electrode changes. When voltage is applied, the tip of the nanotube ejects electrons in a phenomenon called field emission. This ejection is easier when the nanotube is closest to the nanoradio’s positive electrode because the electrons are more likely to jump across this shorter distance. Changing this distance affects how many electrons make it to the other side; the current flowing through the circuit represents the information coded in the carrier wave, essentially decoding it.<\/p>\n

The carbon nanotube thus functions as an antenna, tuner and demodulator. But it’s also the final necessary component of any radio: the amplifier. The strength of the current sent to the speaker corresponds to the voltage the battery sends to the nanotube. Simply hooking up a larger battery, or more of them, to the nanoradio can generate a stronger signal.<\/p>\n

The electrons will jump from the tube’s tip only in a vacuum, so the entire apparatus must be built into a an airtight capsule for it to work. For now, millimetre-size batteries power the radio, but in the future, Zettl predicts, “the radio will be housed in a nanoscale boron-nitride vacuum chamber, which can be inserted into a cell. The biochemistry of the cell itself will be tapped for the energy source, so no battery will be needed.”\u009d<\/p>\n

From nanoscale to nanoradio<\/strong>
\nZettl and his colleagues at COINS stumbled on the nanoradio while devising extremely sensitive scales from nanotubes. Scales and radios may not seem to have much in common, but both work according to the same principles at a nano level. Zettl’s nanoscale is physically almost identical to his radio. Like the radio, the scale’s nanotube vibrates to an electromagnetic radio signal. The difference is that the scale vibrates to a constant carrier wave without any extra information.<\/p>\n

<\/p>\n

Because the scale’s radio signal is constant, the vibrations are as well. A steady stream of electrons passes through the nanotube and then jumps through the electric field. If an object to be weighed is attached to the nanotube, the additional mass changes the tube’s resonant frequency so that it no longer vibrates in sync with the radio wave, and electrons can no longer jump from the nanotube to the positive electrode. The heavier the object that is placed on the nanotube, the more its resonant frequency changes.<\/p>\n

The researchers were able to determine that a frequency change of 0.104 megahertz corresponded to a mass of 4.9 x 10″\u201c24 kilograms. In fact, the scale is capable of weighing materials lighter than one atom of gold. During this research, Zettl realised that some of the nanotube’s frequencies fell within the commercial radio band, spawning the idea for the nanoradio.<\/p>\n

Read more: For the full article, see Science Illustrated <\/em>magazine, July\/August 2010 Australian edition.<\/strong><\/p>\n","protected":false},"excerpt":{"rendered":"

Nanoradios work by using physical vibrations. They won’t change how we listen to music, but they could have a significant impact on the world of medicine.<\/p>\n","protected":false},"author":13,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4,5,9],"tags":[],"class_list":["post-197","post","type-post","status-publish","format-standard","hentry","category-features","category-medicine","category-technology"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/scienceillustrated.com.au\/blog\/wp-json\/wp\/v2\/posts\/197"}],"collection":[{"href":"https:\/\/scienceillustrated.com.au\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/scienceillustrated.com.au\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/scienceillustrated.com.au\/blog\/wp-json\/wp\/v2\/users\/13"}],"replies":[{"embeddable":true,"href":"https:\/\/scienceillustrated.com.au\/blog\/wp-json\/wp\/v2\/comments?post=197"}],"version-history":[{"count":15,"href":"https:\/\/scienceillustrated.com.au\/blog\/wp-json\/wp\/v2\/posts\/197\/revisions"}],"predecessor-version":[{"id":206,"href":"https:\/\/scienceillustrated.com.au\/blog\/wp-json\/wp\/v2\/posts\/197\/revisions\/206"}],"wp:attachment":[{"href":"https:\/\/scienceillustrated.com.au\/blog\/wp-json\/wp\/v2\/media?parent=197"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/scienceillustrated.com.au\/blog\/wp-json\/wp\/v2\/categories?post=197"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/scienceillustrated.com.au\/blog\/wp-json\/wp\/v2\/tags?post=197"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}