Volumetric 3D printing of high-performance, gradient functional organic-inorganic nanocomposites via in situ calcium mineralization

Biomimetic mineralization enhances polymer mechanical properties, but conventional inorganic fillers often induce light scattering and dispersion instability, while solution-mediated mineralization may cause swelling and performance degradation, thereby limiting their use in photocurable 3D printing. In this study, we introduce a combination of volumetric 3D printing and an in situ mineralization strategy through gas diffusion to construct organic–inorganic nanocomposites. By preloading Ca 2+ into the photocurable resin and using a diffusion system containing ammonium bicarbonate, triethylamine, and ethanol, the reaction–diffusion microenvironment was controlled, enabling the in situ nucleation and growth of nanoscale CaCO 3 (∼130 nm) within the printed polymer network. The uniform distribution of nanoparticles and strong interactions led to significant improvements in tensile strength (372%) and toughness (1142%) compared with unmineralized samples. The nanocomposites also showed enhanced cyclic stability and puncture resistance. Leveraging the programmable UV dose distribution inherent in volumetric 3D printing, a gradient in crosslinking density was achieved, which in turn created a gradient distribution of inorganic-phase density and a hierarchical mechanical response to strain. A small amount of PEDOT:PSS was incorporated to endow the nanocomposites with conductivity, broadening their potential applications in flexible strain sensors for human motion monitoring. For the gradient-structured sensor, the sensitivity increased by 1263%, and the response time decreased by 51% compared with the homogeneous material. Together, these findings present a scalable approach to high-performance, gradient-structured 3D-printed organic-inorganic nanocomposites, which are anticipated to expand the scope of functional 3D printing.