Origami artists can turn paper into all manner of ingenious objects. It's unlikely, though, that anyone has tried to make a functioning medical lab that way - until now. With the help of some bits of carpet tape, a portable testing kit made of paper could transform medical care in poor countries.
Much diagnosis depends on tests of body fluids, such as for sugar in urine or viral proteins in mucus. Some such tests are now automated in "labs on a chip" that pipe biological samples through tiny channels into cavities containing reagents that change colour to reveal the result. The trouble is that these microfluidic devices are expensive and fragile.
George M. Whitesides and his Harvard University colleagues cut precise patterns of tiny channels in sheets of paper and interleaved them with double-sided carpet tape laser-drilled with corresponding patterns of holes.
The paper wicks water along the channels, making pumps unnecessary, and the holes connect paper layers to form a three-dimensional maze. Samples applied to one side of the device end up in chambers pre-packed with reagents for different substances. The team's prototype measured sugar in urine, but in principle the device could do many tests at once (Proceedings of the National Academy of Sciences.
A photo of the coloured dots that reveal the results could be sent by cellphone to a specialist centre for diagnosis, and the devices are light, cheap and rugged - good news for healthcare in poor countries.