Ultrasound bubble filter using the flexural vibration of a cylinder for an extracorporeal circulation circuit

•An ultrasound bubble filter without a mesh structure was developed.•The filter utilizes an ultrasound standing wave and removes bubbles.•The filter was designed using FEA.•The total volume of air in the main flow decreased to 1%. An ultrasound bubble filter without a mesh structure was developed for extracorporeal circulation. The filter utilizes an ultrasound standing-wave field generated by flexural vibration and removes micro air bubbles from the circulation. The ultrasound filter consists of an aluminum cylinder, two annular ultrasound transducers, and three connectors to the flow path. The configuration of the filter was determined through finite element analysis computations. Flexural vibrations at 46 and 199kHz were generated in prototypes with lengths of 69 and 130mm. Two driving modes (both standing-wave and traveling-wave modes) were used to evaluate the filtering characteristics in a water circulation system. The bubble size decreased by increasing the input voltage to the filter; the average diameter changed from 60 to under 10μm when the input voltage changed from 0 to 200V. The total volume of air in the main flow estimated from the size distribution of the bubbles decreased to 1% for the 130-mm-long filter excited with the traveling-wave mode.