Additive Manufacturing of Lignocellulosic Aerogels from Minimally Processed Waste Streams

This study showcases the use of lignocellulosic pastes for the additive manufacturing of lightweight and load-bearing porous materials. The pastes are obtained via a milder approach compared to the isolation of conventional cellulose nanomaterials and contain varying lignin contents depending on the extent of bleaching chemistry. The as-produced pastes are compositionally and dimensionally heterogeneous, yet still exhibit excellent printability, enabling the facile fabrication of cellulose-based materials through additive manufacturing. The rheological behavior of these pastes is investigated and their printability is assessed, demonstrating high resolution and shape retention. Upon freeze drying, the printed structures retain their 3-D architecture without any appreciable shrinkage, a key performance indicator in additive manufacturing. Micro-computed tomography is used to investigate the internal structure of the freeze-dried structures, revealing a highly porous scaffold. These constructs possess mechanical strengths comparable to native cork and exhibit promising thermal insulation due to their high porosity. The direct 3D printing of crude lignocellulosic inks to obtain precisely architected structures, whose properties are defined but not limited by the heterogeneous nature of the inks, expands the applications of cellulosic inks in additive manufacturing.