Cactus-inspired freeze-printed SiO₂/ZrO₂ aerogels with programmable configuration for extreme thermal insulation

Aerogels have attracted extensive attention due to their remarkable properties, such as lightweight and low thermal conductivity. However, it remains challenging to simultaneously achieve high temperature insulation (> 1000 °C) and improve mechanical performance. Herein, we report a cactus-inspired spiral structure preparation strategy via freezing-assisted direct ink writing (DIW). By synergistically controlling the rotation angle (θ) and printing spacing (x), we fabricate SiO₂/ZrO₂ aerogels with programmable macroscopic spiral architectures. The SiO₂/ZrO₂ aerogels with θ = 40° and x = 1.3 mm exhibit excellent thermal insulation (30.2 mW·m⁻¹·K⁻¹). However, the compressive strength is only 159.3 kPa at 24.2% fracture strain. To enhance the mechanical performance without compromising thermal insulation, an arctangent-topological DIW strategy is proposed, which employs the arctangent function α_n = arctan(1/n) to fabricate aerogels with four-fold rotational symmetry. When α_n = 26.6° (n = 2), the SiO₂/ZrO₂ aerogels exhibit a favorable thermal insulation performance (33.9 mW·m⁻¹·K⁻¹) while achieving a significant enhancement in compressive strength (341.7 kPa at 24.6% fracture strain). Application of SiO₂/ZrO₂ aerogels for thermal insulation of electronic chips and flame nozzles are demonstrated. The results demonstrate the feasibility of the SiO₂/ZrO₂ aerogels for high temperature applications. This study offers a strategy for developing of high-temperature aerogels with combined good thermal insulation and mechanical properties.