Smartphone-powered microchip for at-home diagnosis

Microfluidics involves the study and manipulation of liquids at a very small scale. A popular application 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, rapid Covid-19 antigen tests being one example. However, a challenge in engineering more sophisticated diagnostic chips — for example, to identify the specific strain of Covid-19 or measure biomarkers like gluclose or cholesterol — is the fact 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. These materials are difficult to scale down to the micro level.

Now, the Minnesota team has reportedly developed 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, an electrical and computer engineering professor and senior author of the study.

“Our thought was, can we just get rid of the cover material, wires and pumps altogether and make it simple?”

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Many lab-on-a-chip technologies work by moving liquid droplets across a microchip to detect the virus pathogens or bacteria inside the sample. Researchers said they were inspired by a real-world phenomenon associated with wine — 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, researchers said they placed tiny electrodes very close together on a 2cm x 2cm chip, which 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 ten nanometers of space between, the resulting electric field is so strong that the chip needs less than a volt of electricity to function, the team said.

This low voltage requirement allowed them to activate the chip using near-field communication signals from a smartphone, the same technology used for contactless payment.

“This is a very exciting, new concept,” said Christopher Ertsgaard, lead author of the study and a recent University alumnus. “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 working with Minnesota start-up GRIP Molecular Technologies to commercialise the microchip platform. The chip is designed to have broad applications for detecting viruses, pathogens, bacteria and other biomarkers in liquid samples.