Tomographic PIV Measurements of a Bio-Inspired Sniffing Rodent

To sample their chemical environments, rodents sniff at high frequencies (8-12 Hz) characterized by complex temporal waveforms. While much is understood about the flow within the nasal passages, the external flow structures generated outside the nares, subsequent evolution in the far-field, and its impact on odor entrainment is not well understood. This is in part due to fast temporal scales and complex 3D flow fields that are a result of complicated animal behaviors and morphologies. To generate and measure sniffing flows, we implemented a tomographic particle image velocimetry (tomo-PIV) system and a bio-inspired robotic sniffer. The sniffer used a 3D printed model based on computed tomography (CT) scans of a rat, and a piezoelectric actuator driving a syringe capable of producing a wide range of sniffing patterns (e.g., square, sinusoidal, bio-inspired) with high fidelity. The tomo-PIV system used four Imager-S CMOS cameras and two Evergreen Nd: YAG 200 mJ/pulse lasers (15 Hz). Here, we present flow fields generated by the robotic sniffer at distinct phases (inhale, exhale, and transitions), which revealed discrete vortical structures and persistent exhalant jets with maximum flows speeds of ~10 m s^-1. Understanding these flow fields provides a foundation for understanding how complex sniffing by rodents increases biological fitness for olfaction.