Tiny wireless sensors inspired by floating seeds could be used to measure environmental factors such as pH 鈥� but they could also have military applications.
at Northwestern University in Illinois and his colleagues have developed sensors whose shape is modelled on seeds like those of maples that spin or glide down to the ground so they can disperse further. Because the sensors are smaller than many of the seeds they mimic 鈥� some are less than a millimetre across 鈥� and can be released from much greater heights, they can stay in the air for longer.
鈥淲e have gliders and spinners,鈥� says Rogers. 鈥淲e do better than naturally occurring seeds.鈥�
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So far, the team has created sensors that can detect pH, heavy metals and exposure to different wavelengths of light. The group also plans to make devices than can capture particulate pollution as they descend.
The wings of the sensors are made from one kind of plastic on top of a stretched out elastic layer, with the heavier electronic components in the middle. The sensors can be manufactured on flat sheets and take on the right shape once cut out, as the bottom layer pulls tight.
The simplest devices just change colour to indicate pH, for instance. The team has also created devices that transmit data via radio frequencies. However, the sensors tested so far are powered by near-field communication circuits like those found in contactless credit cards, meaning they would work only if near an external power source.
鈥淭he manufacturing and design schemes are pretty versatile,鈥� says Rogers. 鈥淲e feel that they will be compatible with a very broad range of electronic components.鈥�
Dropping large numbers of the sensors would create a pollution issue unless they were designed to biodegrade. The degradation rate could be tailored depending on their purpose, says Rogers. Those intended to work on the ground or in water would persist for longer, while sensors for measuring atmospheric properties would degrade much more rapidly.
In theory, the sensors could be used for purposes such as spying, too. 鈥淭hat certainly wasn鈥檛 our intention,鈥� says Rogers, adding that the team didn鈥檛 receive any funding from the military or intelligence agencies. 鈥淏ut any new technology can be used for nefarious purposes.鈥�
Nature
