Fly-by-moth drone

Anthony King

US researchers have created an autonomous drone that can navigate towards smells using an antenna from a moth. In future, the moth antenna could be genetically hacked to sense other smells, say the researchers, such as the volatile chemicals from an unexploded improvised explosive device, or a gas leak.

Competing against a typical sensor in a wind tunnel experiment, the antenna-equipped drone reacted more quickly to a floral scent and took less time to recover between puffs. The researchers dubbed it ‘the smellicopter.’

Cells in the moth antenna detect and amplify chemical signals and then generate an electrical response, measured by wires inserted into the antenna (Bioinspir. Biomim. 2020, 16, 026002). ‘Then we run that through customised circuitry, which amplifies that signal,’ explains Melanie Anderson, a PhD student in mechanical engineering at the University of Washington.

The antennae were removed from Manduca sexta hawkmoths, previously anaesthetised in a fridge. They remained chemically and biologically active for up to four hours. The smellicopter was naturally tuned to head towards smells the moth finds interesting, such as floral scents.

‘The reason we use living tissue is because of its superb sensitivity, speed of reaction and high specificity,’ says group leader Thomas Daniel at Washington. ‘There is no synthetic sensor that can match the chemical sensing in terms of sensitivity.’

The team is to now collaborate with sensory neurobiologist Jeff Riffell, also at Washington, who has previously gene edited mosquitoes, with a focus on chemical sensing genes. This part of the project starts in January 2021 and is funded by the Air Force Center of Excellence on Nature-inspired Flight Technologies and Ideas. It will look to genetically manipulate the odour sensing capabilities of the moth antennae.

‘Through gene editing we can take those proteins that the moth is sensitive to, such as plant volatiles, and remove or lessen them, or amplify proteins that are sensitive to other gases,’ says Anderson, ‘such as human metabolic chemicals, to perhaps find trapped survivors [under rubble].’

This is the first time a moth antenna has been attached to a flying drone, but moth antennae have been paired before with electronics, as so-called electroantennograms.

Commenting on the research, odour researcher Shunsuke Shigaki at Osaka University in Japan notes that integration with the drone must have been by trial-and-error, since electroantennograms are very noisy and also sensitive to drying out, so ‘we guess that the experiment was really tough’.

Shigaki foresees a problem in how long a cut antenna would stay functional. ‘The advantage of using the living antenna is that it can smell several kinds of odours,’ he explains, but ‘if they continue to use cut antenna, they have to develop a long-lasting way of using it.’

ROLF NUSSBAUMER / NATURE PICTURE LIBRARY / SCIENCE PHOTO LIBRARY