Micropumps for lab-on-a-chip disease diagnosis

Researchers from Pennsylvania State University have demonstrated an acoustofluidic pump powered by a piezoelectric transducer the size of a coin. The inexpensive, programmable pump is a crucial feature for lab-on-a-chip devices that could make the diagnosis of many life-threatening diseases easy and affordable.

Tony Huang, a professor of engineering science and mechanics in Penn State’s College of Engineering, noted that it is “difficult to fabricate micropumps that are simple and inexpensive, yet reliable and effective”. But Huang and his team demonstrated that with a smart microfluidic design, low-power acoustic waves could deliver fluids precisely and reliably.

The pump works by oscillating a series of thin sharp-edge structures hundreds of micrometres in length that have been constructed onto the sidewall of a microfluidic channel made of PDMS, a widely used polymer. A miniaturised piezoelectric transducer, similar to the kind used in medical ultrasounds, is the source of the oscillations.

This video shows the real-time pumping behaviour under different input voltages from the piezoelectric transducer.

Writing in the journal Lab on a Chip, the researchers said the “sharp-edge-based acoustofluidic pump is capable of generating stable flow rates as high as 8 μL min^-1 (~76 Pa of pumping pressure)”. The flow rates can be tuned across a wide range, from nanolitres per minute to microlitres per minute.

“Along with its ability to reliably produce stable and tunable flow rates, the acoustofluidic pump is easy to operate and requires minimum hardware, showing great potential for a variety of applications,” the researchers continued.

This video shows the pulsed pumping flow when alternately switching the piezoelectric transducer on and off.

The permanent equipment for the lab-on-a-chip system, including off-the-shelf electronics, could cost as little as $20-$30 to make, while the disposable chip could cost as little as 10 cents, Huang said - in comparison to many diagnostic tests which can cost as much as $800. The system is also far more versatile and precise than paper-based diagnostics, enabling quantitative analysis of HIV, hepatitis, cancer, infectious diseases, cardiovascular diseases and nutritional deficiency.

A silicon mould of the device and the sharp-edged structures on its sidewall were first created using a deep silicon etch tool in the Penn State Nanofabrication Laboratory, followed by a PDMS casting of the device. Eventually, Huang said, the devices and chips could be created using standard automated machine tools controlled by computers for scalable manufacturing. In the future, a battery-powered system could bring affordable disease diagnosis to regions without available electricity.

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