One disadvantage Folch notes is that, because of the paper tests' limited pumping action, they probably won't be able to perform more-complex chemical reactions.

Aside from making the devices cheaper, the designers kept in mind other characteristics that would make them more practical in the developing world. The test's light weight and resistance to breaking make it more portable than tests patterned on easily shattered glass surfaces. The paper chip is also easily disposable, by incineration, a key consideration in developing countries concerned with maintaining public health, says Whitesides. "The kinds of things we're developing here are intended to be useful for screening public health in the developing world," he says. Instead of "taking first-world medicine and trying to downsize it," the team began designing the technology with developing countries in mind, concentrating on ease of use, affordability, and portability, says Whitesides.

In order to optimize the device for developing countries, the team plans to combine the paper tests with a system of cell phones for off-site diagnosis, minimizing the level of expertise needed to use the tests. "It's primarily a way of conserving the valuable time and limited resources of health-care folk," says Whitesides. The team envisions that, in rural areas where doctors are limited, people who are trained only to conduct the tests carry them out "and send them back to a central facility where a doctor looks at that information and [recommends] diagnosis and treatment without having to actually be there," says Whitesides.

As of now, Whiteside and his colleagues have tested the paper diagnostic tool using artificial urine. In a paper published last month, they analyzed the paper results remotely, via phone cameras, and found that the results were "comparable in accuracy" to on-the-spot analysis, says Whitesides.

The next step is a clinical trial and deployment somewhere in Africa, says Sindi. Right now, the team is testing the device under harsh conditions, she says, such as high pressure, temperature, and humidity. So far, the test does not seem to be adversely affected, says Whitesides. The team eventually hopes to move beyond human diagnostics, developing devices for testing water, livestock, and other food sources.

"The kinds of diagnostic assays you want to do and the kinds of problems you want to solve are very diverse in the real world," says Mehmet Fatih Yanik, an assistant professor at the Research Laboratory of Electronics at MIT. "The nice thing about paper is that it's a very flexible platform for conducting a variety of assays." He adds that making microfluidic devices like the Whitesides group's is a lot cheaper than making bulk diagnostic machines. "The combination of the two low-cost systems--the paper-based fluidics and cell phones, which are quite ubiquitous in the developing world--that's a novel idea," says Yanik.

"It really brings a tool that will have a big impact on the implementation of microfluidics," a technology that usually requires a lot of hardware and expertise to use, Folch says. "They've lowered the barrier and are able to bring microfluidics to the masses, so to speak."