EdropSpread · Sustainable Formulation of Emulsion Drops and their Spreading on Complex Surfaces

Pesticides are critical to enhance crop production, with global usage reaching 4.3 million tons, double the amount used in 1990. They are typically formulated as oil-in-water emulsions, where active ingredients are dissolved in oil and stabilized with surfactants to improve adhesion to plant surfaces. After deposition, the water phase of the emulsion evaporates rapidly (<1 minute), while the dispersed oil droplets coalesce to form continuous films that spread outward, a process significantly slower than evaporation. However, less than 1% of the pesticides are absorbed by biological targets, with the majority lost during wetting and spreading on leaf surfaces, contributing to substantial environmental risks. This project, aligned with the goals of the European Green Deal, aims to develop a deeper understanding of the dynamics of emulsion drops at surfaces to optimize pesticide-emulsion formulations and handling protocols, thereby increasing their efficiency.The properties of pesticide-emulsion drops at biomimetic surfaces will be explored for key variables such as surfactant concentration, oil-to-water ratio, and dispersed droplet size. The macroscopic behaviour of emulsion drops during evaporation shall be investigated by optical observations including the internal movement and coalescence of dispersed oil droplets and the formation and spreading of a nanoscopic oil layer by fluorescence microscopy and interference techniques. The microscopic properties of the tested emulsion formulation, like dynamic surface tension, micelle size, and disjoining pressure of the spreading micellar film shall be determined by methods such as dynamic light scattering, electron microscopy and force-distance curves. By quantitatively linking the nanoscopic emulsion properties to the macroscopic behaviour, a predictive model shall be developed, providing a foundation for optimizing the formulation of pesticide emulsions enhancing pesticide uptake and minimizing environmental impact.