The bomb-sniffing cyborg locusts are a reality

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If you want to enhance a locust to be used as a bomb-sniffing bug, there are a few technical challenges that need solving before sending it into the field.

Is there some way to direct the locust – to tell it where to go to do its sniffing?

And because the locusts can’t speak (yet), is there a way to read the brain of these cyborg bugs to know what they’re smelling?

For that matter, can locusts even smell explosives?

Yes and yes to the first two questions. Previous research from Washington University in St. Louis has demonstrated both the ability to control the locusts and the ability to read their brains, so to speak, to discern what it is they are smelling

. And now, thanks to new research from the McKelvey School of Engineering, the third question has been settled.

The answer, again: ‘yes.’

In a pre-proof published online Aug. 6 in the journal Biosensors and Bioelectronics: X, researchers showed how they were able to hijack a locust’s olfactory system to both detect and discriminate between different explosive scents – all within a few hundred milliseconds of exposure.

They were also able to optimize a previously developed biorobotic sensing system that could detect the locusts’ firing neurons and convey that information in a way that told researchers about the smells the locusts were sensing.

“We didn’t know if they’d be able to smell or pinpoint the explosives because they don’t have any meaningful ecological significance,” said Barani Raman, professor of biomedical engineering.

“It was possible that they didn’t care about any of the cues that were meaningful to us in this particular case.”

Previous work in Raman’s lab led to the discovery that the locust olfactory system could be decoded as an ‘or-of-ands’ logical operation. This allowed researchers to determine what a locust was smelling in different contexts.

Explosive vapors were injected via a hole into a box where the locust sat in a tiny vehicle. As the locust was driven around and sniffed different concentrations of vapors, researchers studied its odor-related brain activity. Credit: Raman Lab

With this knowledge, the researchers were able to look for similar patterns when they exposed locusts to vapors from TNT, DNT, RDX, PETN and ammonium nitrate – a chemically diverse set of explosives.

“Most surprisingly,” Raman said, “we could clearly see the neurons responded differently to TNT and DNT, as well as these other explosive chemical vapors.”

With that crucial piece of data, Raman said, “We were ready to get to work. We were optimized.”

Now they knew that the locusts could detect and discriminate between different explosives, but in order to seek out a bomb, a locust would have to know from which direction the odor emanated. Enter the “odor box and locust mobile.”

“You know when you’re close to the coffee shop, the coffee smell is stronger, and when you’re farther away, you smell it less?

That’s what we were looking at,” Raman said. The explosive vapors were injected via a hole in the box where the locust sat in a tiny vehicle.

As the locust was driven around and sniffed different concentrations of vapors, researchers studied its odor-related brain activity.

The signals in the bugs’ brains reflected those differences in vapor concentration.

The next step was to optimize the system for transmitting the locusts’ brain activity. The team, which included Shantanu Chakrabartty, the Clifford W. Murphy Professor in the Preston M. Green Department of Electrical & Systems Engineering, and Srikanth Singamaneni, the Lilyan & E. Lisle Hughes Professor in the Department of Mechanical Engineering & Materials Science, focused the breadth of their expertise on the tiny locust.

In order to do the least harm to the locusts, and to keep them stable in order to accurately record their neural activity, the team came up with a new surgical procedure to attach electrodes that didn’t hinder the locusts’ movement.

With their new instrumentation in place, the neuronal activity of a locust exposed to an explosive smell was resolved into a discernible odor-specific pattern within 500 milliseconds.

“Now we can implant the electrodes, seal the locust and transport them to mobile environments,” Raman said. One day, that environment might be one in which Homeland Security is searching for explosives.

The idea isn’t as strange as it might first sound, Raman said.

“This is not that different from in the old days, when coal miners used canaries,” he said. “People use pigs for finding truffles. It’s a similar approach – using a biological organism – this is just a bit more sophisticated.”


The year was 2016 and the headlines talked about something called cyborg insects and reflected on a branch of technology called biorobotics.

Washington University in St. Louis has made news with their research efforts to use cyborg insects as biorobotic sensing machines.

Translation: University engineers wanted to see if they could capitalize on the sense of smell in locusts for sensing systems that could be used by such departments as homeland security.

Barani Raman, an associate professor at the Washington University’s biomedical engineering, and his team have been studying how sensory signals are received and processed in locusts’ brains.

Fundamental olfactory processing in grasshoppers was in the spotlight; Raman focused on how sensory signals are received and processed in their relatively simple brains and his team fashioned a cyborg sniffer.

Fast forward from 2016 to Monday. New Scientist reported that cyborg grasshoppers have been engineered to sniff out explosives.

How the system works: Bomb-sniffing grasshoppers are kitted out with backpacks. They are engineered to transmit data to reveal explosive chemicals. The signals are transmitted wirelessly to a computer from their attached backpacks.

Again, it was Prof. Raman and colleagues at Washington University in St. Louis, featured this time for having tapped into “the olfactory senses of the Schistocerca americana, to create bomb sniffers, uniting sensors of a grasshopper with electronics.

Donna Lu reported in New Scientist that these tiny lightweight sensor backpacks fitted to the grasshoppers “were able to record and wirelessly transmit the electrical activity almost instantaneously to a computer.”

What gives insects a special edge on sniffing out dangerous systems?

New Scientist: Consider olfactory receptor neurons in the antennae. They pick up on chemical odors in the air. They send electrical signals to a part of the insect brain known as the antennal lobe. Each grasshopper antenna has approximately 50,000 of these neurons.

In their testing, the team implanted tiny electrodes into the insects’ antennal lobes and puffed vapors of different explosive materials.

The non-explosive controls were hot air and benzaldehyde. Vapors of different explosive materials puffed into the antennae included TNT and DNT.

“The last step was to fit grasshoppers with a sensor ‘backpack’ which would record and transmit their neural activity in real-time to a computer, where it would be interpreted,” said ZME Science.

What were the test results? Recordings of neural activity from seven grasshoppers were around 80 percent accurate,

“The grasshoppers’ brains continued to successfully detect explosives up to seven hours after the researchers implanted the electrodes, before they became fatigued and ultimately died,” said Lu.

Not only that, and also impressive: “The grasshoppers were able to detect where the highest concentration of explosives was when the team moved the platform to different locations,” said New Scientist.

The paper “Explosive sensing with insect-based biorobots” is up on the preprint server bioRxiv. The authors stated that “We demonstrate a bio-robotic chemical sensing approach where signals from an insect brain are directly utilized to detect and distinguish various explosive chemical vapors.”

They said in their paper that they believed their approach was not that different from the ‘canary in a coal mine’ approach, “where the viability of the entire organism is used as an indicator of absence/presence of toxic gases.”

More information: Debajit Saha et al. Explosive sensing with insect-based biorobots, biorxiv (2020). DOI: 10.1101/2020.02.10.940866


More information: Debajit Saha et al, Explosive sensing with insect-based biorobots, Biosensors and Bioelectronics: X (2020). DOI: 10.1016/j.biosx.2020.100050

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