On-package Additively Manufactured Chemiresistive Sensors for Smart Agriculture: Detection of Airborne Sex Pheromone of Domestic Silk Moths

Domestic silk moths, Bombyx mori, which have been bred for centuries, are insects that play a leading role in the production of silk, an economically valuable and highly sought-after natural fiber. Female domestic silk moths produce two types of sex pheromones, named bombykol and bombykal, respectively. Even though detection of the sex pheromones of domestic silk moths has great economic and academic significance, related work has rarely been reported. In this work, flexile carbon nanotube-based chemiresistive sensors, which were amine-functionalized and additively manufactured via inkjet-printing and drop-casting, were used to target the aldehyde sex pheromone bombykal. Domestic silk moths were home-raised starting from Bombyx mori silkworm eggs. Female silk moths, which produce the two types of sex pheromones, were used as the analyte in this work. Custom-designed boxes were 3D-printed in-house to facilitate the pheromone building-up and their exposure to the sensors. Sensing trials were performed in air under ambient conditions with a commercial data acquisition system, automated with home-developed LabVIEW-based programs. A typical sensor showed prompt and significant response upon exposure to the airborne pheromone vapor emitted by 10 female silk moths, achieving a relative sensitivity of 1.2% after 10 minute exposure. A sensing mechanism, which involves the chemical reaction between the aldehyde group of the sex pheromone bombykal and the surface amine groups on the sensors, is proposed.