Silicon dioxide (SiO2) aerogel has become the most widely used aerogel material due to its high porosity, high pore volume, large specific surface area, excellent thermal insulation, acoustic impedance, flame retardant and other characteristics. Its sol gel preparation process makes SiO2 based aero gel mainly molded by mold casting, which is difficult to obtain complex three-dimensional structure. The emergence of 3D printing technology provides the possibility to build customized SiO2 based aerogels with complex macro morphology. Among them, UV curing 3D printing can achieve higher construction accuracy and rapid large-scale manufacturing. However, photocuring 3D printing relies on photocuring of photosensitive resin to realize 3D manufacturing. The introduction of photosensitive groups in the precursor will significantly reduce the intrinsic characteristics of aerogel products. The removal of organic components by post-processing will inevitably damage the structure of aerogel.

The Institute of Chemistry of the Chinese Academy of Sciences has realized the preparation of SiO2 based aerogels by digital light processing (DLP) 3D printing at extremely low acrylate content by exploring the time evolution of the photorefractive behavior of acrylate modified silica sol during hydrolysis condensation. The content of SiO2, skeleton intrinsic density and physical structure characteristics of the obtained aerogels are similar to those of commercial SiO2 aerogels, and show more excellent mechanical properties at low apparent density. Furthermore, taking advantage of the opening characteristics of the three-dimensional framework of the aerogel, the printed SiO2 based aerogel was used as the nano engineering platform, and other functional materials were filled to obtain high-performance multi-functional interpenetrating phase nanocomposites with complex macro structure. The specific bending strength of the composite material with epoxy resin is 107 ± 6 MPa/g − 1 · cm3, which exceeds that of most metals, ceramics and natural mother oysters; The composite with ionic gel realizes the decoupling of mechanical properties and conductivity. The elastic modulus of the composite is nearly 1400 times higher than that of gel, while the ionic conductivity is almost unchanged.

Figure 1. Preparation route, morphology and structure of SiO2 based aerogel printed by DLP

Figure 2. Mechanical properties and flame retardancy of DLP printed SiO2 based aerogel

Figure 3. Preparation route, morphology and mechanical properties of aerogel epoxy matrix interpenetrating phase nanocomposites

Figure 4. Aerogel ion gel/hydrogel interpenetrating phase nanocomposites

This study shows that the traditional sol gel process can match with the UV curing 3D printing technology, reduce the over dependence of the printing process on UV curing through the spontaneous sol gel transition, and achieve the preparation of complex macrostructures while retaining the intrinsic properties of materials. This strategy can be extended to other sol gel systems such as titanium, aluminum, vanadium and zirconium, greatly expanding the range of UV curing 3D printing materials.