This device can test four samples for four different analytes. Researchers dipped each corner of the device into artificial urine to detect glucose and protein. Liquid samples move through the device to different test zones. Turning white to brown shows the presence of glucose, while yellow to blue indicates protein.

Paper the size of postage stamps inlaid with different patterns of proteins can perform as diagnostic medical devices. By simply adding tape, Harvard University professor George Whitesides and his team have been able to turn their paper tests into 3D devices for more-complicated analysis. Such paper lab-on-a-chip tests may lead to cost-effective, portable, and accurate methods for diagnosing diseases in countries lacking appropriate laboratories.

Until now, microfluidic systems require channeling fluids. Researchers, however, can direct a liquid by placing water-resistant channels in the paper using waterproof tape. Whitesides’ latest development is a square covered in a grid of red, yellow, green, and blue dots and made of several layers. Waterproof layers separate each. Layering the squares and connecting them with tape sends liquid horizontally and vertically through the small space.

Treating each square of paper with a photoresist material creates channels that direct liquid to tiny wells coated with proteins or antibodies. A tiny hole in the waterproof tape funnels liquid to the next paper or layer. Flow continues through each layer of the chip, and results appear in a dotted grid on the final layer. Body fluid from a patient would interact with the proteins and turn the well a particular color indicating, for example, varying concentrations of glucose.

The team focused on materials that will make it reliable and useful in a variety of environments and developing countries. The natural capillary action in paper avoids pumps and power sources to move the liquid (as are needed for polymer or glass microfluidic devices). Whitesides’s goals are to design portable tests that are cheap to manufacture, easy to use, and can diagnose many ailments. Although tests are still in R&D, Whitesides says they have been accurate.

Researchers have also begun work on coupling paper tests with cell phones, so results can be photographed, sent to a distant medical center, and read by a technician who can phone back recommendations.