Aerobiology with Acoustic Levitation*

Airborne microbes critically impact our everyday lives, e.g., rainfall, disease spread, land fertilization, and food production. Often these microbes hitchhike on particulates – often referred to as bioparticulates – which can remain suspended in the atmosphere and undergo intercontinental transits. Detailed laboratory studies of airborne microbiota are essential for understanding Earth's ecosystems, yet current studies mostly dwell on soil/marine microbiota. Acoustic levitation is one possible route to investigating airborne microbes in the lab by imitating atmospheric conditions and testing different particulates without physical contact. With this goal in mind, we investigated various designs of acoustic levitators to optimize acoustic trapping forces while remaining cost-effective and scalable. Utilizing an array of ultrasonic transducers roughly based on the TinyLev design, we levitated materials of different densities such as polystyrene, volcanic pumice, glass, water, and light metals. Furthermore, we test the performance of our acoustic levitators in different environmental conditions by varying the humidity, temperature, pressure, and other physical conditions relevant to the mechanics of airborne particles. These results will be useful in understanding the survival of airborne microorganisms in the troposphere.