Tech Reduces Runoff Pollution By Making Spray Droplets Less Bouncy

When farmers spray their fields with pesticides or other treatments, only 2 percent of the spray sticks to the plants while a significant portion becomes part of the runoff that flows to streams and rivers - often causing serious pollution. MIT researchers have developed a way to make droplets less bouncy, which could help drastically cut down on the amount of pesticide liquid that bounces off plants. The new approach uses two different kinds of additives. The spray is divided into two portions, each receiving a different polymer substance. One gives the solution a negative electric charge; the other causes a positive charge. When two of the oppositely-charged droplets meet on a leaf surface, they form a hydrophilic (water attracting) 'defect' that sticks to the surface and increases the retention of further droplets.