Creation of cavitation activity in a microfluidic device through acoustically driven capillary wavesElectronic supplementary information (ESI) available: Movie 1-The development of acoustic cavitation showing the generations of surface instability, gas bubble pulsation, bubble splitting, and large area cavitation; gas on top and water below. The width of the frame is 500 μm. The driving frequency of the PZT transducer is 103 kHz and the driving voltage is 230 V. The video was recorded at 125 000

• Main Authors: Tandiono, Ohl, Siew-Wan, Ow, Dave Siak-Wei, Klaseboer, Evert, Wong, Victor V. T, Camattari, Andrea, Ohl, Claus-Dieter
• Format: Article
• Language: English
• ISSN: 1473-0197; 1473-0189
• DOI: 10.1039/c002363a

We present a study on achieving intense acoustic cavitation generated by ultrasonic vibrations in polydimethylsiloxane (PDMS) based microfluidic devices. The substrate to which the PDMS is bonded was forced into oscillation with a simple piezoelectric transducer attached at 5 mm from the device to a microscopic glass slide. The transducer was operated at 100 kHz with driving voltages ranging between 20 V and 230 V. Close to the glass surface, pressure and vibration amplitudes of up to 20 bar and 400 nm were measured respectively. It is found that this strong forcing leads to the excitation of nonlinear surface waves when gas-liquid interfaces are present in the microfluidic channels. Also, it is observed that nuclei leading to intense inertial cavitation are generated by the entrapment of gas pockets at those interfaces. Subsequently, cavitation bubble clusters with void fractions of more than 50% are recorded with high-speed photography at up to 250 000 frames/s. The cavitation clusters can be sustained through the continuous injection of gas using a T-junction in the microfluidic device. Intense inertial cavitation in PDMS based microfluidics is achieved from gas bubble entrapment of strongly driven capillary waves.