A team at Penn State has developed a system for conducting a wide range of medical and other tests using nothing more than a slip of paper the size of a stick of gum. These slips, which reveal chemical markers that can point to serious diseases or contamination, are designed to be cheap, portable, easily used and fully functional without power. (click below to read more)
The slips are layered constructions combining different types of paper and chemicals that variously channel liquids and react with them. The scientists used their invention to measure two enzymes, one indicative of liver health and another that serves as a marker for fecal contamination of water.
To use the technology, you'd take a slip made to detect the thing you are looking for and apply blood or some other liquid to it. Then you wait for one of two white dots on the slip to turn green. At that point you start keeping time until a second dot turns green. The longer the second change takes, the higher the concentration of the detected marker. Measurement times range from 30 seconds to 15 minutes.
Why the two dots? The strip is divided into two sections, an assay area and a control area. Since humidity and sample viscosity affect the rate at which a substance is distributed through the paper, the coloring of the first dot indicates that the liquid has been sufficiently distributed through the paper so that the real test, on the assay side, can begin.
The researchers note that their special paper, despite its structured design, requires only inexpensive materials. But by making slips with different reagents, or detection chemicals, batches of the slips could be customized for measuring different biochemical markers, and therefore different diseases or contaminants.
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