Researchers at the A*STAR Institute of High Performance Computing, Nanyang Technological University, and the A*STAR Bioprocessing Technology Institute are aiming to trap bubbles inside a microfluidic chip to enable the release of concentrated energy pulses that can reach pressures as high as 100 mPa and temperatures upto 5000K.
This concentrated energy surge is termed as cavitation and is capable of driving chemical reactions as well as biological applications.
A blue glow reveals bursts of energy associated with the collapse of bubbles close to the interface between liquid (green dashed line) and gas
Researchers proposed a process that by producing bubbles within liquids of sub-micro liter volumes present in the narrow pathways of a microfluidic chip, it is possible to control the cavitations position. A lot of complexities arise due to presence of bubbles within narrow pathways. Wall boundaries can obstruct collapse of bubbles, thus resulting in energy dissipation.
To validate the idea, the researchers developed microfluidic equipment with an ultrasound-producing transducer. They then filled an aqueous solution of a luminous chemical, luminal, with tiny quantities of gas into the narrow pathways of the microfluidic equipment. They discovered that the energy produced from cavitation could result in the splitting of the water molecules, thus producing hydroxide radicals that react with the luminol to emit blue light. They discovered that the chip emitted a blue light with each burst of ultrasound.
The images captured show that the gas confined inside the pathways split up into tiny bubbles that consequently collapsed violently owing to the pressure waves arising from the ultrasound vibration.
Tandiono from the A*STAR Institute of High Performance Computing stated that they want to achieve an overall understanding of the properties of bubble collapse in the microfluidic pathway and its relation to sonochemistry. Systematic studies can be performed as the oscillating bubbles are confined within a well-defined boundary within the microfluidic pathway.
Following this, the researchers hope to study the link between sonoluminescence, sonochemical reactions, and bubble dynamics, says Tandiono. The microfluidic equipment is useful for various biological research applications. They also hope to make use of acoustic bubbles in microfluidics to suit some biological applications, including gene delivery and cell disruption.