The first text message sent entirely with molecules has been issued by using evaporated vodka. A vodka spray was turned into a binary code by varying concentration levels – to signal 0 or 1 meaning ‘alcohol’ or ‘no alcohol’ – and transmitted, and the message decoded by a receiving device as: ‘O Canada’.
The scientists from the University of Warwick, UK, and York University in Toronto, Canada, say chemical signalling could replace radio communications in situations such as in industrial plants, hospital settings or deep inside tunnels or pipelines, where they perform poorly. ‘Smell always propagates well in these kinds of tricky environments,’ says author Weisi Guo of Warwick. And the technique could be scaled up by introducing different chemicals into the mix.
The initial setup was very straightforward and relied on a single type of chemical. However, a vast mixture of compounds, each transmitting its own code, could be used. ’If I could use say a couple of million different compounds, I could get a massive data transfer rate,’ says Guo.
The scientists chose a cheap chemical and the receiver was a breathalyser sensor. An off-the-shelf version cost $100; a customised version came to $300. They also kept their communication code and algorithms to turn vodka into code as simple as possible in this proof of principle (PLoS ONE, doi: 10.1371/journal.pone.0082935).
‘One of the chief factors holding back developments in [molecular communication] is the availability of small, inexpensive, sensitive, selective and fast responding chemical sensors,’ commented systems engineer Andrew Russell at Monash University, Australia. ‘As chemical sensor technology improves the range of feasible applications will really take-off.’ Russell has used air pulses to allow mobile robots to communicate with one another (Robotics and Autonomous Systems, doi:10.1016/j.robot.2010.11.002).
Molecular communication is of interest for nanobots in health applications. Electromagnetic waves are no good for communication inside the body, as the antenna size must be proportional to the wavelength, and lasers are no good because accurate alignment is impossible.
The authors note that they could only send short messages in their setup, but the volume of data sent could be improved by using better fans, more sophisticated protocols and detection algorithms, use of multiple chemicals, multiple-input and multiple-output communication, designing better sensors, and using sensor arrays.
Massimiliano Pierobon at the University of Nebraska-Lincoln, US, says molecular communication could allow communication between implantable devices, including cells engineered to deliver drugs. His group recently developed a theoretical model for better drug delivery to the cardiovascular system (EEE Transactions on Biomedical Engineering, doi: 10.1109/TBME.2013.2271503). ‘From an application point of view [the PLOS paper] is interesting, but it is not a breakthrough paper. You could do the same with smoke signals in my opinion.’