Cyborg Grasshoppers That Detect Bombs
A group of scientists led by Barani Raman at Washington University in St. Louis, Missouri, have re-engineered the olfactory system of the American grasshopper, "Schistocera americana," to invent biological bomb detectors.
The olfactory receptor neurons of insect antennae detect local airborne chemical odors. The neurons then send electrical signals to a section of the insect brain called the antennal lobe. Every grasshopper antenna has roughly 50,000 such neurons.
The St. Louis team puffed vapors of various explosive materials onto grasshopper antennae, including the vapor of trinitrotoluene (TNT), and its precursor 2,4-dinitrotoluene (DNT). The scientists used non-explosive controls like benzaldehyde and hot air, the former of which is the main ingredient for bitter almond oil.
While implanting electrodes in the antennal lobes of grasshoppers, the team discovered groups of neurons that activated when exposed to explosive materials. The further analysis of electrical signals allowed them to distinguish explosive from non-explosive vapors, and also from one another.
Short lifespan, longterm applications
To monitor the electrical activity in real-time, the team equipped the grasshoppers with lightweight sensor backpacks capable of recording and wirelessly transmitting information to a computer.
The cyborg grasshoppers' brains successfully continued to detect explosives for up to seven hours, post-op, until the insects became fatigued, and died.
The process immobilizes grasshoppers, so the scientists put them on wheeled, remote-controlled platform, to study the insects' ability to detect explosives at varying locations and direction.
Since real-world chemicals could be dispersed by varying environmental forces — like wind — the scientists also studied the effects of sensory information combined from multiple grasshoppers.
A seven-grasshopper dataset showed an average accuracy of 80%, significantly higher than the 60% achieved by a singular grasshopper.
While the scientists didn't test the grasshoppers' bomb-sniffing ability when several odors were present at the same time, bomb threats of the future may see a swarm of locusts descend, instead of bomb-sniffing dogs to which we've become accustomed.