Yager's team designed a device in which they varied the lengths of paper that led from three reagent sources to a common reaction site, providing a way to control the timing of reactions.

The team demonstrated the amplification of a color indicator linked to a molecule associated with a disease. This allows the disease to be detected visually even if the tell-tale molecule is present only in very low concentrations. This is a crucial part of several clinical tests, but had not yet been carried out on paper because of its complexity--needing different reagents at different times. The team's results were published this month in Sensors and Actuators and Microfluidics and Nanofluidics.

The new devices will be entirely self-sufficient and can be operated by without training. "What we're doing is throwing away the pumps, throwing away the hardware, and keeping the full complexity of the microfluidics we've worked on in the last 15 years," says Yager.

Bernhard Weigl, the director at the Center for Point-of-Care Diagnostics for Global Health, says that paper tests like the one Yager's team is developing could be used to detect a range of diseases, with just one sample, "as samples can be guided to different reagent sites from a single distribution point," he says. Weigl is collaborating with Yager's team to develop and test the device.

Now that the team has shown that the amplification step is possible, they are working on ways to optimize and package the technology for distribution. The end result is expected to be a paper-based device, laminated in plastic for protection, with a lens to make the results visible.