Microbubble Generation By Piezoelectric Transducers For Biomedical Studies

Mohammed Alkhazal, Old Dominion University


Bubbles induced by blast waves or shocks are speculated as the major cause of damage in biological cells in mild traumatic brain injuries (TBI). Microbubble collapse was found to induce noticeable cell detachment from the cell substrate, changes in focal adhesion, and biomechanics. To better understand the bubble mechanism, a system needs to be constructed which allows clear differentiation on the impact of bubbles from that of shocks. Such a generator needs to be low profile in order to place under a microscope. A piezoelectric transducer system was designed to meet the need. The system uses either a flat or a spherical focusing piezoelectric transducer to produce microbubbles in a cuvette loaded with cell-culture medium. Several transducer configurations were designed and tested. The first design has a transducer that faces upward in a water chamber, so that the pressure waves can reach a coverslip placed above the transducer. To allow for the light passage, the transducer was drilled at the center and a hole was created. This configuration was found not easy to use as it created water jets at the water surface when water level was shallow. A second configuration where the transducer was placed on the side of the cuvette with its axis lining horizontally was then designed. A cover slip was placed on the top of the cuvette. The impact of the waves to the cells was minimized as the cover slip was parallel to the direction of the wave. Only bubbles from the medium could reach the cover slip and interact with cells. The effect of bubbles, therefore, can be separated that of pressure waves. The bubbles collected on a cover slip range in size from 10 μm to 100 μm in radius, but the dominant size is 10-30 μm.