The lower right red dot indicates that this CHEMCARD paper test is ready (Photo: Scott T. Phillips)
Throughout the world, reactive paper-based systems are used to test peoples’ blood, urine and other bodily fluids for biomarkers that indicate everything from diabetes to pregnancy. Such systems are also used to detect pollution in water. However, for many of these tests to be accurate, an exact amount of time must pass between the application of the fluid and the viewing of the paper – if the paper is observed any earlier or later, the perceived results could be inaccurate. People typically use stopwatches to avoid this problem, but not everyone in the world has access to such devices, so scientists from Pennsylvania State University (PSU) have developed a simple timer that can be built into the paper itself.
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