3D-printed programmable hierarchical hole-cavity architectures of fully cellulose nanofibrils for tunable broadband...

The integration of broadband sound absorption with environmental sustainability remains a key challenge in advanced material design. In this work, an innovative 3D-printed cellulose nanofibril (CNF) architecture with a customizable hierarchical "hole-cavity unity" structure was proposed for highly efficient sound absorption. This multi-scale structural design strategy synergistically coupled the perforated-panel acoustic principles with nanoscale viscous dissipation mechanisms. By leveraging the shear-thinning behavior of CNF inks and the precision control of direct ink writing, the sub-millimeter periodic pore arrays were embedded within the continuous nanofibrous network, enabling programmable structural tunability across multiple pore scales. Systematic regulation of infill ratio and sample thickness yielded high sound absorption coefficients (>0.7) over an ultra-broad frequency range of 1.2-6.3 kHz. Combined with low shrinkage, structural customizability, low density, and rapid environmental degradability, the fully bio-based 3D-printed CNF architectures are expected to offer a promising and sustainable solution for developing next-generation acoustic materials for noise control applications.