Minimalist microfluidic chip powered by a smartphone

Researchers at the University of Minnesota have developed a new microfluidic chip for diagnosing diseases that uses a minimal number of components and can be powered wirelessly by a smartphone. Described in the journal Nature Communications, the innovation opens the door for faster and more affordable at-home medical testing.

Microfluidics involves the study and manipulation of liquids at a very small scale. One of the most popular applications in the field is developing ‘lab-on-a-chip’ technology, or the ability to create devices that can diagnose diseases from a very small biological sample such as blood or urine.

Scientists already have portable devices for diagnosing some conditions, such as rapid antigen tests for COVID-19. However, a big roadblock to engineering more sophisticated diagnostic chips is the fact that they need so many moving parts. Chips like these would require materials to seal the liquid inside, pumps and tubing to manipulate the liquid and wires to activate those pumps — all materials difficult to scale down to the micro level. The Minnesota team was able to create a microfluidic device that functions without all of those bulky components.

“It’s not an exaggeration that a state-of-the-art, microfluidic lab-on-a-chip system is very labour-intensive to put together,” said Sang-Hyun Oh, senior author of the new study. “Our thought was, can we just get rid of the cover material, wires and pumps altogether and make it simple?”

Many lab-on-a-chip technologies work by moving liquid droplets across a microchip to detect the virus pathogens or bacteria inside the sample. The researchers’ solution was inspired by a peculiar real-world phenomenon with which wine drinkers will be familiar — the ‘legs’, or long droplets, that form inside a wine bottle due to surface tension caused by the evaporation of alcohol. Using a technique pioneered by Oh’s lab, the researchers placed tiny electrodes very close together on a 2 x 2 cm chip; the electrodes generate strong electric fields that pull droplets across the chip and create a similar ‘leg’ of liquid to detect the molecules within.

Because the electrodes are placed so closely together, with only 10 nm of space between, the resulting electric field is so strong that the chip needs less than a volt of electricity to function. This incredibly low voltage requirement allowed the team to activate the chip using near-field communication signals from a smartphone, the same technology used for contactless payment in stores. It is also believed to be the first time researchers have been able to use a smartphone to wirelessly activate narrow channels without microfluidic structures.

“This is a very exciting, new concept,” said Minnesota alumnus and lead author Christopher Ertsgaard. “During this pandemic, I think everyone has realised the importance of at-home, rapid, point-of-care diagnostics. And there are technologies available, but we need faster and more sensitive techniques. With scaling and high-density manufacturing, we can bring these sophisticated technologies to at-home diagnostics at a more affordable cost.”

Oh’s lab is now working with startup company GRIP Molecular Technologies, which manufactures at-home diagnostic devices, to commercialise the microchip platform. The chip is designed to have broad applications for detecting viruses, pathogens, bacteria and other biomarkers in liquid samples.

Image credit: ©stock.adobe.com/au/metamorworks

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