Cactus-inspired freeze-printed SiO2/ZrO2 aerogels with programmable configuration for extreme thermal insulation
Aerogels are promising for thermal insulation due to their lightweight and low thermal conductivity, yet achieving high-temperature resistance (>1000 °C) alongside robust mechanical performance remains challenging. Here, we report a cactus-inspired spiral structure strategy via freezing-assisted direct ink writing (DIW). By controlling the rotation angle (θ) and printing spacing (x), we fabricate SiO2/ZrO2 aerogels with programmable macroscopic spiral architectures. The aerogel with θ = 40° and x = 1.3 mm exhibits excellent thermal insulation (30.2 mW·m−1·K−1) but limited compressive strength (159.3 kPa at 24.2% fracture strain). To enhance mechanical properties without compromising insulation, we propose an arctangent-topological DIW strategy using αn = arctan(1/n) to create four-fold rotational symmetry. At αn = 26.6° (n = 2), the aerogel achieves a thermal conductivity of 33.9 mW·m−1·K−1 and a compressive strength of 341.7 kPa at 24.6% fracture strain, representing a significant improvement. Finite element simulations (COMSOL Multiphysics) corroborate experimental results. Demonstrations on electronic chips and flame nozzles confirm effective thermal protection. This work provides a viable route to aerogels with integrated high-temperature stability and mechanical robustness.