Using coffee-ring effect, scientists boosted sensitivity of diagnostic tests by pre-concentrating disease biomarkers into a ring pattern.
Turns out, coffee stains and cutting-edge medical tests have quite a lot in common.
A new at-home diagnostic technology developed by researchers at the University of California, Berkeley uses the same physics behind coffee rings to dramatically boost the sensitivity of rapid tests.
Coffee or wine stain often leaves a darker ring around the edges than at the center, a phenomenon known as the “coffee-ring effect.” As a droplet evaporates, it pushes particles outward, concentrating them along the rim.
Where stains meet science
The UC Berkeley team realized they could use this natural process to concentrate disease markers in a test sample, making them easier to detect.
The result is a low-cost, easy-to-use device that’s up to 100 times more sensitivethan current at-home COVID-19 tests and could one day help detect life-threatening conditions like sepsis and prostate cancer in just 12 minutes.
The innovation combines the “coffee-ring effect” with plasmonic nanoparticles and an AI-powered app to detect trace amounts of disease biomarkers in a single droplet.
When the sample dries, it concentrates the target proteins at the edge of the ring. Special nanoparticles are then added, which bind to these proteins and create light patterns that can be identified visually or through a smartphone.
“This simple yet effective technique can offer highly accurate results in a fraction of the time compared to traditional diagnostic methods,” said Kamyar Behrouzi, who recently completed a Ph.D. from UC Berkeley.
“Our work paves the way for more affordable, accessible diagnostics, especially in low-resource settings.”
Prototype at-home test kit includes a 3D printed scaffold to help guide users on where to place the droplets (upper left), a syringe (upper right), and a small electric heater to speed evaporation (lower right). Credit -Kamyar Behrouzi
The rapid test works by using plasmonic nanoparticles, the tiny particles that interact with light in distinctive ways.
Rings, light, and logic
To begin, a user places a droplet of liquid, such as from a nasal or cheek swab, onto a membrane. As the droplet dries, it naturally pulls any disease-related proteins toward the outer edge, forming a concentrated coffee-ring pattern.
A second droplet, this time containing specially engineered nanoparticles, is then added. These nanoparticles are designed to bind to the disease biomarkers.
If the biomarkers are present, the particles cluster in patterns that alter how light reflects off the membrane, a change that can be seen with the naked eye or detected through an AI-powered smartphone app.
“One of the key proteins that we are able to detect with this method is a biomarker of sepsis, a life-threatening inflammatory response to a bacterial infection that can develop rapidly in people over 50,” said study senior author Liwei Lin.
“Every hour is critical, but culturing bacteria to determine the source of the infection can take a few days. Our technique could help doctors detect sepsis in 10 to 15 minutes.”
The researchers have developed a prototype home testing kit, much like existing at-home COVID tests that includes 3D-printed components to guide users in placing the sample and plasmonic droplets accurately.
“During the COVID-19 pandemic, we relied on at-home tests to know if we were infected or not,” Lin said.
“I hope that our technology makes it easier and more accessible for people to regularly screen for conditions like prostate cancer without leaving the home.”
The findings have been published in the journal Nature Communications.
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