NEW DELHI, INDIA: Diagnostic tools that are cheap to make, simple to use, and rugged enough for rural areas could save thousands of lives in poor parts of the world.

To make such devices, Harvard University Professor George Whitesides is coupling advanced microfluidics with one of humankind's oldest technologies: paper.

The result is a versatile, disposable test that can check a tiny amount of urine or blood for evidence of infectious diseases or chronic conditions, reports the inaugural issue of the Indian edition of Technology Review, a 109-year magazine from Massachusetts Institute of Technology (MIT).

The finished devices are squares of paper roughly the size of postage stamps. The edge of a square is dipped into a urine sample or pressed against a drop of blood, and the liquid moves through channels into testing wells.

Depending on the chemicals present, different reactions occur in the wells, turning the paper blue, red, yellow, or green. A reference key is used to interpret the results, elaborates the article from Technology Review, to be launched by the noted policy maker Prof MGK Menon at MIT's Emerging Technologies conclave here next week.

The squares take advantage of paper's natural ability to rapidly soak up liquids, thus circumventing the need for pumps and other mechanical components common in microfluidic devices.

A small drop of liquid, such as blood or urine, wicks in through the corner of the paper and passes through channels to special testing zones. Substances in these zones react with specific chemicals in the sample to indicate different conditions; results show up as varying colors. these tests are small, simple, and inexpensive.

Paper is easily incinerated, making it easy to safely dispose of used tests. And while paper-based diagnostics (such as pregnancy tests) already exist, Whitesides's device has an important advantage: a single square can perform many reactions, giving it the potential to diagnose a range of conditions. Whitesides also wants to develop tests for infectious diseases such as tuberculosis.

The Harvard researchers have made the paper chips into a three-dimensional diagnostic device by layering them with punctured pieces of waterproof tape. A drop of liquid can move across channels and into wells on the first sheet, diffuse down through the holes in the tape, and react in test wells on the second paper layer.

The ability to perform many more tests and even carry out two-step reactions with a single sample will enable the device to detect diseases (like malaria or HIV) that require more complicated assays, such as those that use antibodies. Results appear after five minutes to half an hour, depending on the test.

The researchers hope the advanced version of the test can eventually be mass produced using the same printing technology that churns out newspapers. Cost for the materials should be three to five cents. At that price the tests will have a big impact on health care in areas where transportation and energy access is difficult.

Currently, Whitesides is developing a test to diagnose liver failure, which is indicated by elevated levels of certain enzymes in blood. People without consistent access to health care do not have that luxury; a paper-based test could give them the same safety margin.