Multi-material additive manufacturing of polymeric composites with seamless soft-hard interface integration from molecular bonding

Multi-material additive manufacturing (AM) enables the fabrication of functionally graded three-dimensional (3D) structures by integrating multiple materials with dramatically different properties. However, it remains a grand challenge to develop a robust multi-material AM process that allows for joining parts with distinct mechanical properties. Here, we report multi-material stereolithography (SLA) printing of polymeric composites with seamless soft-hard interface integration from molecular bonding. Exploiting our recently discovered foldable bottlebrush polymer networks, we develop photocurable resins with Young’s moduli ranging by more than three orders of magnitude from ~40 kPa to ~150 MPa. Importantly, all resins are cured by the same chemistry, such that polymers of dramatically different stiffness can be bonded at the molecular level. We customize an SLA platform to print these resins into multi-material tensile bars, which exhibit remarkable stretchability (with tensile breaking strain >700%) determined primarily by the softer component. Further, we demonstrate printing multi-material polymeric composites with spatially resolved mechanical properties and seamless soft-hard interface integration. The developed polymeric resins and multi-material SLA process open an avenue for manufacturing functional 3D multi-material polymeric structures and devices for a wide range of applications.