Hybrid Additive Manufacturing of Highly Stretchable Bottlebrush Polymer Nanocomposites by Decoupled Extrusion and Photopatterning

Abstract

Polymer nanocomposites offer opportunities for engineering soft materials that combine mechanical robustness with multifunctionality. However, their additive manufacturing remains challenging because high nanoparticle loading simultaneously increases viscosity and optical opacity, making these materials incompatible with conventional vat photopolymerization. Existing hybrid direct‐ink‐writing/digital‐light‐processing (DIW–DLP) systems typically process different materials independently rather than photopatterning the same composite ink deposited by extrusion. Here, we introduce a hybrid DIW–DLP (HDD) strategy based on the hypothesis that sufficiently thin layers of opaque polymer nanocomposites can still undergo rapid photocuring. In HDD, extrusion deposits thin layers of composite ink, while projected UV light independently defines geometry and lateral resolution, decoupling material deposition from shape control. This strategy enables sub‐nozzle‐gauge photopatterning and allows the uncured ink to function as a removable, self‐supporting scaffold for embedded structures inaccessible to conventional DIW or DLP. In parallel, we develop bottlebrush polymer–cellulose nanocrystal (CNC) composite inks with extremely high viscosity (up to 3 × 10 5 Pa·s) that, upon curing, exhibit an exceptional combination of softness and stretchability (Young's modulus ∼20–120 kPa; tensile strain >1600%). Together, this work establishes a framework for photopatterning highly viscous composite inks and introduces a new class of stretchable bottlebrush nanocomposites for fabricating mechanically robust, geometrically complex soft materials.