Stretchable\nMetamaterials with Tunable Infrared Emissivity\nfor Dynamic Thermal Management

Manipulation of infrared emissivity,\nwhich is closely related to\nsurface structure and optical parameters of materials, is a crucial\napproach for realizing dynamic thermal management. In this study,\nwe design a metamaterial consisting of an array of aluminum disks\nembedded on a surface of a stretchable elastomeric substrate. Mechanical\nstretching-induced deformation allows dynamic modification of the\nsurface structure and equivalent optical parameters, thus enabling\ndynamic control of the emissivity. By utilizing the elastomer polydimethylsiloxane\n(PDMS) as the substrate, the microstructure interdisk gap can be altered\nby stretching the PDMS. Through theoretical calculations, the plausibility\nof this approach is explained by the excitation of plasmon resonance\nand the variation in the exposed area of highly absorbent PDMS, and\nthe optimal structures for tuning the infrared emissivity are revealed\nto be 6 μm in diameter and 100 nm in height. Based on this design,\nwe prepare samples with periods of 7 and 7.9 μm and experimentally\ndemonstrate that a change in the period can cause a change in the\nemissivity and thus tunability in thermal control performance. The\ntemperature difference between the two samples reaches 44.1 °C\nat a heating power of 0.28 W/cm<sup>2</sup> for both samples. Furthermore,\nwe construct a stretching platform that enables in situ mechanical\nstretching to realize dynamic changes in emissivity. The integral\ninfrared emissivity of the sample increases from 0.32 to 0.5 at a\nbiaxial tensile strain of 13%, achieving a 56% modulation rate of\nthe integral infrared emissivity. The material is expected to enable\ndynamic thermal management.