Bio-sourced, oven-dried and wet-stable foams based on cellulose and amyloid nanofibrils

In the recent decades, foams have been extensively used for different applications such as: packaging, thermal and acoustic insulation, energy storage, and water purification. However, fabrication of foams from renewable resources through green methods with scale-up potential is challenging. In this context, cellulose nanofibrils (CNFs) as the most abundant bio-derived nanofibrils with outstanding physical properties such as high aspect ratio and elastic modulus and particular surface chemistry are very attractive. Another bio-sourced nanomaterial that has emerged recently is amyloid nanofibril (ANF). ANFs can be prepared from whey protein which is highly available as a by-product of dairy companies. In addition to high aspect ratio and surface functionality, ANFs are surface active and can form stable wet foams. In this project, we prepare biohybrid foams by a simple up-scalable method: blending and oven drying.  ANFs are used as foaming component and CNFs as wet foam stabilizers. To enhance stability of foams upon convection drying different types of covalent cross-linkers are successfully introduced.

The composition of the foams is optimized and the foams are characterized cautiously. The density, porosity, BET specific surface area, dry and wet mechanical properties, water adsorption capacity, and acid/base resistance of the foams are measured. Moreover, in order to have a better understanding of the mechanism for stability of the foams, rheological time-sweep tests are performed. Finally, confocal microscopy is performed to determine the location of fibrils in the foams. X-ray tomography is planned to be performed to measure the pore size of these foams and to determine how the pore sizes change by swelling of the foams in water.