Activation-retardation in sol-gel reactions for additive manufacturing of transparent poly(methylsilsesquioxane) aerogels.

Coupling superior thermal insulation performance with high transparency for solar transmission and excellent processability in aerogels is a challenging yet promising subject. Here, we report a direct ink writing strategy to create transparent polymethylsilsesquioxane (PMSQ) aerogels from gel inks with desired rheology, by merely using acid-base dual modulators to achieve "activation-retardation" of polycondensation reaction. The printed aerogels are pure PMSQ, have a transmittance of 97% in the visible-near infrared range, thermal conductivity (16.2 mW m-1 K-1) lower than that of still air, and low density (0.08 g cm-3). We demonstrate new possibilities of our 3D-printed transparent aerogels, such as device encapsulation for heat insulation and cylindrical cooling shields for lighting.