Illustration showing a ring of disease biomarkers, in purple, interacting with a droplet of liquid that contains plasmonic nanoparticles. (Image courtesy of the researchers)From drop to diagnosis
Look at any coffee stain, and you’ll see that the outline is much darker than the interior. This “coffee-ring effect” occurs when a droplet of liquid evaporates, pushing suspended particles toward the edge. If the particles are pigmented, as in coffee, the stain’s rim appears darker around the rim than its center. Now, Berkeley engineers have harnessed this phenomenon to create low-cost, rapid, at-home diagnostic tests up to 100 times more sensitive to viruses.
“This simple yet effective technique can offer highly accurate results in a fraction of the time compared to traditional diagnostic methods,” said Kamyar Behrouzi (M.S.’21, Ph.D.’24 ME). “Our work paves the way for more affordable, accessible diagnostics, especially in low-resource settings.”
The technology uses tiny plasmonic nanoparticles that interact with light in unique ways. To conduct the test, a user adds a droplet of liquid containing disease-relevant proteins — from a cheek or nasal swab — to a membrane. As the droplet dries, it concentrates any biomarkers at the coffee ring.
A second droplet containing plasmonic nanoparticles that have been engineered to stick to the disease biomarkers is then added. If biomarkers are present, the nanoparticles aggregate in patterns that change how light interacts with the membrane — providing results that are visible to the eye or 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,” said Liwei Lin, professor of mechanical engineering. “Our technique could help doctors detect sepsis in 10 to 15 minutes.”
Learn more: From COVID to cancer, new at-home test spots disease with startling accuracy (Berkeley News); Plasmonic coffee-ring biosensing for AI-assisted point-of-care diagnostics (Nature Communications)