Mitigating the Coffee-Ring effect exhibited by pesticide solutions on pepper leaves using amphiphilic berberine sulfate microgels

Nonuniform deposition of pesticide droplets on crops and their runoff create excessive pesticide waste, posing a major threat to public health and the environment. Microgels are a class of soft colloids that combine the properties of solid particles and polymers to regulate the resistance of pesticides to rainwater runoff and mitigate the coffee-ring effect (CRE). In this study, we developed amphiphilic calcium alginate microgels (UAMs) capable of enhancing the pesticide evaporation uniformity and the deposition of berberine sulfate (BS) on a target crop, as well as its surface adhesion. A BS-loaded UAM (UAM–BS) solution was sprayed onto the surface of pepper leaves. The gel coating contained flexible and complex networks, which are easily entangled with the microstructures on the leaf surface. This ultimately resulted in the removal of the interface void and the improvement of the BS deposition uniformity at multiple scales. In addition, the surfactivity of the microgels was regulated through grafting, which affected the uniformity of the liquid film deposition. Furthermore, the effect of UAM–BS on pepper anthracnose was investigated, and its control efficacy was found to be over 80%. Additionally, it could improve the BS deposition uniformity and adhesion while mitigating the CRE. This study establishes the use of alginate-based gel coatings as a promising strategy for improving pesticide utilization while addressing the issues of easy runoff and nonuniform deposition. The findings will prove valuable in the fields of bionic materials science, bio-macromolecular chemistry, and agricultural science.