Dip and test: This three-dimensional device can test four samples for four different analytes. The researchers dipped each corner of the device into artificial urine samples to detect glucose and protein. Samples move through the device into the different test zones. White to brown shows the presence of glucose, while yellow to blue indicates protein. (The first sample had neither glucose nor protein.)
According to Whitesides, “Each dot would be a different test” that could be performed using a single drop of blood serum. Currently, the researchers layer the paper and tape by hand, which Whitesides says is fairly easy to do, but they hope that eventually a device could be made to print the tape and paper.
The group has focused on readily accessible materials, so the device can be robust and used in a variety of environments and in developing countries. They chose paper because its natural capillary action circumvents the need for expensive or cumbersome pumps and power sources to move the liquid (as would be needed for polymer or glass microfluidic devices). In that way, the device is similar to how pH paper or a pregnancy test works. But Whitesides aims for his tests to diagnose much more, as well as be portable, cheap to manufacture, and easy for those in developing countries or in military or emergency respond teams to use and adapt.
“These paper-based devices may allow significantly cheaper and portable analytical devices for diagnostics in the developing countries,” says Mehmet Fatih Yanik, an assistant professor of electrical engineering at MIT, who works on lab-on-a-chip imaging. “They could also allow routine conduction of hundreds of assays cheaply, which may allow early and precise diagnostics of severe diseases, significantly reducing the health-care burden,” he adds.
Although the tests are still in the research and development phase, Whitesides says, so far, they seem to be highly accurate. Whitesides has already cofounded a nonprofit, Diagnostics for All, to further develop and distribute the tests in a developing country. (Diagnostics for All won the MIT $100K Entrepreneurship Competition earlier this year.)
The researchers have also begun work on coupling the paper tests with cell phones, so that the results can be photographed, sent to a center, and read by a technician who can send recommendations back via phone.