Butterfly Wing Microstructure Inspired Solid/Porous Alternating Layered Structures: In Situ Visualization of Confined...

This study explores confined foaming in micro-/nano-layered (MNL) solid/porous alternating structures inspired by the hierarchical architecture of Ulysses butterfly wings. Biomimetic MNL films composed of alternating polycarbonate (PC) and polymethyl methacrylate (PMMA) layers (17-513 layers) are fabricated via advanced coextrusion and foaming techniques. In situ visualization reveals confinement effects dependent on layer thickness; while nucleation primarily occurrs at PC/PMMA interfaces due to reduced energy barriers, a strong confinement zone within 10 µm of the interfaces significantly restricts cell growth, most notably in the 129-layer and 513-layer samples, where single-cell rows are observed. Thermal regulation tests show that the 513-layer bio-mimic structure reduces temperature rise by 80%, 65%, and 50% compared to polyethylene (PE) film, a three-layer sandwich structure, and butterfly wings, respectively. It also exhibits exceptional delay in heat accumulation under radiative conditions, with a time to reach half of the maximum temperature rise of 165 s, compared to 20 s (PE) and 40 s (both three-layer and butterfly wing). The bio-mimic architecture also exhibits strong anisotropic thermal conductivity, effectively suppressing through-thickness heat transfer while enhancing lateral dissipation. These results connect nature-inspired design and practical implementation, highlighting the potential of bio-mimic MNL structures for advanced thermal management applications.