A non-invasive, low frequency resonant method to detect bubbles in liquid media

Abstract

Reliable detection technology of gas and vapor filled bubbles in fluid media is of paramount importance for many medical and industrial processes. In this work we present an acoustic bubble detection technique. A single element transducer device simultaneously performing as projector and receiver capable of generating well-controlled low frequency standing pressure waves in a resonant acoustic glass chamber. The electrical properties of the transducer reflect changes in the elastic properties of the fluid media due to the presence of bubbles that perturb the resonant state of the acoustic chamber, providing the bubble detection mechanism. This allows the usage of electrical resonance of the transducer as a proxy measurement for determining the mechanical resonance of the chamber. Our results show reproducible detection of a 7.5 mm long and 5.2 mm wide Taylor bubble in the form of a current drop across the transducer. Positive results were also obtained with bubbles of 2 and 0.6 mm in diameter. The device proved to work effectively at low power (<1 Watt) making it highly stable over long operation times. Additionally, by taking advantage of the transducer’s electrical properties as a proxy for the resonant state of the enclosed volume, the operation is non-invasive and adaptable to other geometries.