LEAPS-MPS: Glass Particle-filled Fungal Composites with Advanced Mechanical Properties through a Nutritive Hydrogel-based Interfacial Engineering

NON-TECHNICAL SUMMARY: The biological growth of filamentous fungi cells (hyphae) and their bonding with substrate particles leads to highly sustainable composite materials called fungal composites. Practical approaches to improve fungal composite mechanical properties are necessary to realize this potential fully. A promising approach to improving fungal composite mechanical properties is reinforcing the substrate with rigid fillers, as commonly used for synthetic polymer composites. The fundamental challenge underlying this approach is that hyphae do not bind naturally to synthetic particles to form the composite due to a lack of nutrient elements. This project will support research on understanding mechanisms to promote bonding between fungal hyphae and synthetic particles to obtain improved mechanical properties in fungal composites that rival traditional composites. The findings from this study will support the development of advanced fungal materials that will advance national technological leadership in biological materials and conserve national non-renewable resources, which will result in significant societal and economic benefits. Additionally, the project will contribute to STEM workforce development on biological materials through outreach activities for K-12 students and research opportunities for undergraduate and graduate students. TECHNICAL SUMMARY: This project will support fundamental materials research on understanding the mechanisms that govern the interfacial bonding of fungal hyphae with synthetic particles to develop novel fungal composites. These composites use glass beads as reinforcing fillers through a rational design of the interface between hyphal matrix and glass beads. Specifically, the research will aim to design a hydrogel-based interfacial layer supplemented with nutritional elements for glass particles that will promote hyphae-particle interfacial bonding. Hydrogel composition and material properties will be tailored to support invasive hyphal penetration into the hydrogel layer through the exertion of mechanical force. A systematic study will be performed to understand the complex interactions between hydrogel material properties, nutrition content, fungal species, and particle-hyphae interface structure. The effectiveness of hydrogel-based interfacial engineering will be evaluated through systematic measurements of hyphae-particle interfacial bonding strength and macro-scale mechanical properties of glass-filled fungal composites. A novel particle-filled fiber network model will be implemented to understand microstructural deformation and failure mechanisms not accessible experimentally. The model will be validated with respect to mechanical testing data and used to establish structure-property relations. Together, effective ways will be identified to control hyphae-glass particle bonding strength and concomitantly achieve dramatic composite reinforcement through rigid glass particles. Additionally, the project will broaden participation and contribute to STEM workforce development on biological materials through outreach activities for K-12 students and research opportunities for undergraduate and graduate students. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.