Although plants always give off VOCs during the regular gas-exchange process, certain types and/or concentrations of the chemicals are associated with specific diseases. That's where the new handheld reader-type gadget comes in. Developed by scientists at North Carolina State University, it's designed to be attached to a farmer's smartphone, sitting over top of its camera lens.
That farmer starts by pulling a leaf off the plant in question, and placing it in a test tube which is subsequently sealed for at least 15 minutes – this gives the leaf a good amount of time to release its VOCs. Next, the tube is uncapped and a thin length of plastic tubing is used to pump the accumulated chemical gases from the test tube into a chamber within the reader.
Inside of that chamber is a strip of test paper, which contains spots of embedded reagents that change color when exposed to certain VOCs. Some of those reagents consist of off-the-shelf dyes, while others incorporate custom-altered gold nanoparticles. The phone's camera images those spots, providing an onscreen display.
Presently, users have to manually interpret the displayed strip's color pattern (pictured below), determining which VOCs are present in the chamber, and in what amounts. Once an accompanying app is developed, however, it will automatically alert users if a disease is indicated, telling them which one it is.