Biomedical engineers from Washington University in St Louis have implanted electrodes into the brains of grasshoppers, allowing them to exploit the jumping insects excellent sense of smell.

The engineers selected the American grasshopper as the subject of their experimentation on account of its sophisticated olfactory (scent detection) system. The grasshopper's antennae contain olfactory receptors which are used to sniff for food and predators. Information from these receptors are transmitted to 50,000 neurons in a part of their brain called the antennal lobe.

According to Professor Barani Raman, who has been working on insect-based sensory systems at the universitys biomedical engineering department for years, these qualities could make grasshoppers better at detecting explosives than any device in existence.

In order to exploit the grasshoppers sense of smell, Raman and his colleagues implanted electrodes into the olfactory centres of their brains.

They puffed vapours of different explosive materials at the grasshoppers: dynamite (TNT) and 2,4-Dinitrotoluene (DNT), with benzaldehyde and hot air as controls. They measured the neural activity triggered by each of the compounds and found that with some practice they were able to distinguish between the different vapours within a second, simply by observing the grasshoppers neural activity.

Finally, Raman and his colleagues fitted the grasshoppers with a lightweight sensor 'backpack'. This device records and wirelessly transmits their neural activity to a computer, which interprets this data in real time.

The enhanced grasshoppers could detect and distinguish between explosive compounds correctly for up to several hours after the electrodes were implanted. A single grasshopper could detect explosives with an accuracy of 60 per cent, while a seven-grasshopper team had an average accuracy of 80 per cent.

Our study provides the first demonstration of how biological olfactory systems (sensors and computations) can be hijacked to develop a cyborg chemical sensing approach, the engineers wrote in their study.

Sadly for the grasshoppers, the mechanisation procedure comes at the cost of their mobility, resulting in the researchers pushing their unfortunate subjects around on a wheeled, remote-controlled platform to test them in different locations and orientations. The grasshoppers also died of fatigue after about seven hours of work.

The study, which was funded by the US Office of Naval Research, could eventually lead to the deployment of cyborg grasshoppers for homeland security purposes. For instance, a swarm of upgraded insects could be deployed to the scene of bomb threats in the future as an alternative to valuable working dogs.

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'Cyborg' grasshopper engineered to sniff explosives - E&T Magazine