A reception with light refreshments will be held in the B32 lobby before the seminar from 1-1:30 p.m.

Abstract: The replacement of synthetic nanomaterials with biodegradable alternatives made from abundant and sustainable raw materials is a challenge of high societal importance. We will discuss how the process of antisolvent precipitation under shear enables the formation of diverse classes of biopolymer structures, including nanoparticles, rods, nanofibers, nanoribbons, sheets, and hierarchical nanomaterials. Specifically, we will focus on the unique capabilities enabled by a new class of soft dendritic colloids (SDCs) with hierarchical morphology (Nature Materials 18:1315, 2019). The fractal branching and contact splitting phenomena enable a range of highly unusual properties of the SDCs – gelation at very low volume fractions, strong adhesion to surfaces and to each other, and ability to form new types of gels, nonwoven sheets and reinforced biocomposites. Alginate SDCs can be used in hierarchical hydrogel networks with synergistic combination of the colloidal and molecular networks (Nature Comm. 12:2834, 2021). One emerging application of the SDCs with high societal impact is as cleaners that capture microplastics for water remediation (Langmuir 40:5923, 2024). We further make use of the unique properties of the SDCs in “active microcleaners,” which are made of chitosan and infused with a small amount of fatty acid, enabling them to self-propel and self-disperse in water by the Marangoni effect. The rehydrated SDCs could enable the cleanup of microplastics in various types of aquifers, including saline seawater. Finally, we report a class of high-performance multifunctional composite films made of biopolymers: agarose matrix reinforced with chitosan SDCs. Owing to the highly entangled hierarchical SDCs network, the reinforced biocomposites have excellent mechanical performance, high optical transmittance, hydrostability, bactericidal activity and soil biodegradability (Cell Rep. Phys. Sci. 4:101732, 2023). The results suggest a universal strategy for manufacturing of natural-source composite materials that can serve as substitutes for petroleum-based plastics.

Speaker Bio: Dr. Orlin Velev is a Frank and Doris Culberson Distinguished Professor at NC State University. He received his PhD degree from the University of Sofia, Bulgaria (1996), while also performing research for one year in Japan. After a postdoc at the University of Delaware Velev joined NC State University in 2001. He has established a record of innovative research in the assembly of colloidal nanostructures with magnetic, electrical, and photonic functionality, biosensors, microfluidics and manufacturing of environmentally friendly and sustainable nanomaterials. Velev has contributed more than 240 publications and has presented more than 310 invited presentations. He has received numerous awards, including NSF Career, AIChE Andreas Acrivos Award for Professional Progress, AIChE Braskem Award for Excellence in Materials Engineering and Science, and ACS Langmuir Lecturer.