Chemiresistively sensitized SiOC structure for formaldehyde detection under thermal and pressure loading

Chemiresistive SiOC Negative Poisson's ratio structures for gas detection under thermal and pressure loading were constructed by vat photopolymerization and surface sensitization. Metal-organic framework-derived SnO₂ nanocubes modification provided the structures with sensing capability, while the high deformation-resistant SiOC substrates protected the integrity and connectivity of the sensing layer. The resulting SnO₂/SiOC sensing structures exhibited high selectivity to formaldehyde vapor and showed a response value of 3.6 to 100 ppm formaldehyde vapor. The structures also had a short sensing delay with the response and recovery times of 32 s and 41 s, respectively. Besides, the independent deformation of the units maintained the dimensional accuracy and avoided thermal fatigue failure of the structure at the working temperature by dispersing the thermal stress, at which the coefficient of thermal expansion reached 0.71 × 10⁻⁶/K, revealing a near-zero expansion behavior. Meanwhile, the mechanical performance can be adjusted by structure optimization, and the compressive strength and Young's modulus of the structure reached 51.25 MPa and 5.14 GPa, respectively. Taking advantage of the strengthened and self-adaptive design, the structure exhibited high load-carrying capacity and low thermal expansion performance, providing a facile strategy for highly stable gas detection under complex loading environments.