Canine-inspired Unidirectional Flows for Improving Memory Effects in Machine Olfaction.

In a dog's nose, air flows unidirectionally from the nostrils' inlet to its outlet. Previous simulations showed that unidirectional flow through a dog's complex nasal passageways creates stagnant zones of trapped air. We hypothesize that these zones give the dog a "physical memory" which it may use to compare recent odors to past ones. In this study, we conducted experiments with our previously built Gaseous Recognition Oscillatory Machine Integrating Technology (GROMIT) and perform corresponding simulations in two dimensions. We compared three settings: a control setting that mimics the bidirectional flow of the human nose, a short-circuit setting where odors exit before reaching the sensors, and a unidirectional configuration using a dedicated inlet and outlet that most mimics the dog's nose. After exposure to odors, the sensors in the unidirectional setting showed the slowest return to their baseline level, indicative of memory effects. Simulations showed that both short-circuit and unidirectional flows created trapped recirculation zones which slows the release of odors from the chamber. In the future, the memory effects such as the ones found here may improve the sensitivity and utility of electronic noses.