Real-time odor concentration and direction recognition for efficient odor source localization using a small bio-hybrid drone

Small drones with biosensor devices have great potential for detecting odorant molecules in air and can be applied to environmental and security monitoring. To realize these applications, two important factors are considered: first, development of highly sensitive, selective, and real-time odorant sensor devices, and second, construction of a highly maneuverable platform with efficient odor source localization. Previously, small drones with commercial gas sensors or biosensors based on insect antennae have been developed. However, the performance of gas sensors proved to be inadequate for real-time sensing; the flight performance of a bio-hybrid drone was limited because the yaw turn was not considered and flight tests were conducted in a wind tunnel. In this study, we developed a fully autonomous small drone with a portable electroantennogram (EAG) based on silkmoth antennae mounted on it. The EAG device was also equipped with a sensor enclosure to enhance sensor directivity. The bio-hybrid drone can recognize real-time odorant concentration differences in a pseudo-open environment (outside the wind tunnel). We also developed an enclosure for enhancing the sensor directivity of EAG. Owing to the enclosure, the drone could distinguish the front-back direction in the odor plume without a wind direction sensor. Based on these results, the drone recognized the maximum value of odorant concentration during an over 360° yaw turn and localized the odor source using the spiral-surge algorithm without any assumption of the upwind direction. This study proposes an efficient flight platform for detecting odorant molecules in air and localizing their sources.