Pinch-off Dynamics of CNC-Stabilized Foam and Emulsion Filaments

Particle-stabilized foams and emulsions are ideal colloidal dispersions to be used as ink in drop-on-demand 3D printing systems. These unique systems provide the advantageous capability of encapsulating both hydrophilic and hydrophobic cargoes within the printed texture, offering versatile material properties. Emulsions and foams, in particular, enable the exchange of species between the printed frame and the surrounding media, allowing precise control over porosity by manipulating the droplet size distribution. In this study, we investigate the pinch-off dynamics of a colloidal system made of cellulose nanocrystals (CNC)-stabilized foams and emulsions. We find that the viscoelastic properties of our colloidal systems play a crucial role in the dynamics of filament break-up, regardless of dispersed phase state, i.e. water droplets (emulsion) or gas droplets (foam). The concentration of CNCs is found to be critical in the long-term stability and printability for Pickering foams and emulsions. To facilitate practical implementation, we develop a comprehensive printability map that outlines the necessary conditions for CNC-based materials to be effectively utilized in drop-on-demand and direct ink-writing 3D printing technologies.