Smart plankton to 'see' underwater


By David Robson Plankton may be thought of as lowly creatures. But gadgets that copy their drifter lifestyle could improve our understanding of the world’s oceans. Italian researchers are working on “smart plankton”, which will carry sensors and communicate using flashing lights. Released in groups, they could drift through the ocean collecting data. This is a watery take on an idea dubbed “smart dust“, already used to monitor environmental conditions on land and tipped to transform extra-planetary exploration. The smart dust model uses many small, cheap sensors that communicate wirelessly to track environmental conditions over wide areas. Davide Brizzolara says that using a similar approach in the oceans will provide greater coverage than static underwater sensors do, and would be cheaper than using autonomous underwater vehicles. He is developing the smart plankton with colleagues at SmartLab at the University of Genoa, Italy. The team hope that smart plankton swarms containing thousands of individuals will help environmental monitoring, underwater archaeological surveys and mine detection. Each sensor will collect data such as water temperature or salinity as it moves with the ocean currents. Information will be relayed from plankton to plankton back to a fixed hub on a floating buoy that collates the data. Smart dust on land communicates using radio waves. But underwater, such a signal cannot penetrate more than a metre or so. Instead, inspired by photo-luminescent plankton, Brizzolara’s current design uses flashing LEDs to send messages. The researchers found that visible wavelengths of light are scattered less by underwater particles, such as real plankton and sediment than radio waves are. The best wavelength to use varies depending on the size of the particles, so our plankton will be adaptable, says Brizzolara. “If the communication bit rate falls below a certain rate it can switch to another colour, to see if the communication improves.” This should allow nodes up to 10 metres apart to communicate at bit rates around 1 gigabit per second – similar to a home broadband connection. Measuring the delay will also allow an estimate of the distance between nodes and the fixed buoy. The team is currently working on a large proof-of-principle prototype roughly 20 cm in diameter, but plan to reduce the size to smaller than 2 cm per unit. The plankton will draw power from small piezoelectric flags that flutter in the surrounding water and produce voltage as they move. But the model plankton may not need to be shrunk, says John Barker from the University of Glasgow, UK, who is developing smart dust for exploring other planets such as Mars. “The advantage of the plankton model is that the swarm could drift on real currents and retrieve information on temperature and salinity in physically important regions. There is no need to make it small.” However, he points out the smart plankton still needs considerable development and testing before they are ready for their first dip. A paper on smart plankton was presented at Alife Conference in Winchester,
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