At scale production of biodegradable microcapsules that can control the release of active ingredients is a key technological step to mitigate the environmental impact of intentionally added microplastics, which play an important role in our daily life but are causing health concerns and are targeted by ever stringent regulations on their use. Conventional microplastics are known to last for a long time, move in various ecosystems, and accumulate in living organisms along food chains. Nonetheless, stringent performance criteria such as a precisely controlled release profile and the complex manufacturing of emerging materials hinder the replacement of commonly used microcapsules with biodegradable alternatives. Here, we demonstrate that microencapsulation in a biopolymer such as silk fibroin can be achieved by modulating the structural protein protonation and chain relaxation at the point of material assembly. Manufacturing through well-established fabrication techniques such as spray drying yields microcapsules with tunable morphology and degradation kinetics. It can sustain the release of soluble and insoluble payloads typically used in cosmetic and agriculture applications. As a proof-of-concept for agrochemicals delivery, a greenhouse trial demonstrated that a commonly used herbicide (i.e., Saflufenacil) delivered via
silk microcapsules on corn plants reduced crop injury compared to the non-encapsulated version.
The second part of the talk will focus on the advanced architectures assembled from silk protein microunits. Compared with spherical particles, the hierarchically structured microparticles show enhanced adhesive and frictional properties, and provide reaction points at the interface of complex features. These results provide a fundamental understanding of silk-like polymer polymorphism and promising applications such as long-term delivery and environmentally responsive devices.