Adaptive 4D printing of infrared stealth materials based on temperature-responsive emissivity tunability and thermal insulation coupling.

Adaptive infrared stealth technology, as an important means of target feature control, has a core contradiction in the synergistic realization of environmental adaptability and structural functionality. 4D printing provides a new paradigm for the realization of structural time-varying response to material intrinsic properties by exploiting the stimulus-responsive properties of shape memory polymers (SMPs). Inspired by the flower petal's blooming structure, a 4D adaptive infrared stealth material PP-N-VO was developed by DLP light-curing printing technology and coating process. PP-N-VO has temperature-responsive 4D dynamic properties (from 3 mm to 8 mm in height). The microscopic porous structure inside the material and the air layer generated by the contraction of the petal morphology contribute to the temperature control (equilibrium temperatures at the surface of the heat source are only 46.1 °C at 100 °C). The surface VO coating reduces the emissivity of the material after reaching the phase transition temperature (from 0.942 to 0.623). It is worth noting that NIPAAM and tungsten-doped 1.5 wt% VO phase transition temperature is close to the response temperature of the contraction morphology. This dual-responsive effect not only produces an air layer to enhance the effect of thermal insulation, but also makes the surface of the infrared emissivity reduction (within 1 min), thus achieving the efficient infrared stealth. Therefore, this intelligent 4D stealth material with responsive temperature adaptation performance is expected to become a potential candidate for emerging intelligent materials in the field of infrared stealth, meeting the needs of high-temperature equipment.