Gelation-Constrained Freeze-Casting Fabrication of Ultra-Homogeneous Nanocomposite Aerogels with Superelasticity and Harsh Environment Tolerance

Abstract

Freeze casting is a versatile technique for organizing low-dimensional building blocks into ordered porous structural materials. However, the freeze-casting fabrication of porous materials with a robust and topologically elastic skeleton to withstand harsh conditions is challenging. Herein, a silanized ultra-homogeneous nanocomposite aerogel is fabricated using a gelation-constrained freeze-casting strategy. Diverging from traditional freeze-casting methods employing a solution precursor, the approach involves a gelation-constrained freeze-casting process utilizing a rational-designed supramolecular hydrogel as the quasi-solid precursor. The low-dimensional building blocks within the hydrogel, enclosed in a dense hydrogen-bonded network, effectively mitigate secondary agglomeration caused by ice crystallization and concentration enrichment during freeze-casting. By forming a topologically elastic cellular skeleton with an interconnected nanoparticle network, the resulting aerogels exhibit exceptional mechanical elasticity retaining over 98% height after 10 000 compression cycles, along with superior electrical properties showing a 78.9% increase in conductivity compared to conventional freeze-casting aerogels. Wearable piezoresistive sensors with these aerogels demonstrate outstanding force sensing capabilities, showing a broad linear range (0–17.6 kPa) and high sensitivity (1.32 kPa⁻¹). When integrated as an intermediate layer in protective garments, these sensors offer exceptional insulation and fire resistance, enabling them to endure harsh conditions like repetitive extreme deformations, exposure to high-temperature flames, and water-erosion damages.