Self-timer for medical paper strip
Scientists from Pennsylvania State University (PSU) have developed a simple timer that can be built into the paper itself, that lets home users and clinicians know when the results are ready.
Scott Phillips and Hyeran Noh designed the timer, which involves treating part of the test paper with dye and paraffin wax. When a fluid sample is placed on the paper, some of it begins to react with the traditional reagents that will ultimately provide the results, while some of it begins to wick through microchannels in the wax, picking up the dye along the way. Once the fluid gets through the wax to the bottom layer of the paper, it causes a dot in one region of the paper to change color, indicating that the time is up. The amount of time that can be measured ranges from one minute to two hours, and is determined by how much wax is used. The system has also been modified to emit a sound when the time is up, or even to glow.
Source: gizmag.comAdded: 14 December 2010