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.
The project was developed in collaboration with the MIT Tata Center for Technology and Design, which aims to develop technologies that can benefit communities in India as well as throughout the developing world. Spraying of pesticides there is typically done manually with tanks carried on farmers’ backs, and since the cost of pesticides can be a significant part of a farmer’s budget, reducing the amount that’s wasted could improve the overall economics of the small-farming business, while also reducing soil and water pollution. Decreasing the amount of pesticide sprayed can also reduce the exposure of farmers to the spray chemicals.
Based on the laboratory tests, the team estimates that the new system could allow farmers to get the same effects by using only 1/10 as much of the pesticide or other spray. And the polymer additives themselves are natural and biodegradable, so will not contribute to the runoff pollution.
The new approach would require only minor changes to the existing equipment that farmers use, to separate the pesticide into two streams to which small amounts of each polymer could be added. The polymers themselves are extracted from common, low-cost materials that could be produced locally.
In addition to pesticide spraying, the same approach could be useful in other applications, such as the spraying of water onto plants to prevent frost damage in places like Florida, where citrus crops can be severely damaged by frost but water supplies are already constrained.