A simple system for encoding messages in puffs of alcohol – including vodka – and transmitting them through the air has been used to send a simple text message. The researchers in the UK and Canada claim that this is the first example of the kind of chemical signalling used by animals and plants being mimicked to send a message in the lab.
Since the invention of the electrical telegraph, the principal carrier for human communications has been electromagnetic waves, from the electrical pulses that carried telegrams down wires to the frequency modulated radio waves that transmit mobile phone calls through the air. But when this method is impractical, such as on scales smaller than the wavelength of electromagnetic waves, one alternative, inspired by nature, is chemical signalling.
Nariman Farsad and Andrew Eckford at York University, and Weisi Guo at the University of Warwick set up a simple chemical signalling system by encoding the phrase ‘O Canada’ as a stream of ones and zeroes using an established binary alphabet. They then transmitted the message up to 4 metres using spritzes of isopropyl alcohol – although it also worked with vodka – to represent either a one or a zero. To ensure a constant airflow in one direction the researchers used a fan.
An alcohol gas sensor downwind of the spray provided a voltage that increased with alcohol concentration. The researchers decoded the original binary message by changes in voltage.
The researchers noticed non-linearities in the response of the sensor that had not been predicted by theoretical models, and Farsad explains that they are working to characterise these to allow better theoretical models that should help them design improved communication protocols. ‘We're also trying to shrink it down,’ says Eckford. ‘The ultimate goal is to be able to say something about micro- and nanoscale communication.’
Sasi Balasubramaniam, an electronics and communications postdoc at Tampere University of Technology in Finland, however, points out that the molecules themselves do not actually encode any information. ‘The whole idea of molecular communication is to allow communication between nanomachines that have very limited capacity in a biological environment,’ says Balasubramaniam. This could be achieved by encoding the information into molecules, bacteria or viruses, he adds. ‘You can't just use a bottle of spray, spray it and say: “Hey, that's molecular communication”.’
‘If you wanted to realise a communication system you could use smoke signals,’ agrees Massimiliano Pierobon of the University of Nebraska-Lincoln. ‘This is more or less the same thing done with a spray and a little electronic sensor.’