Interdigitated Three-Dimensional Heterogeneous Nanocomposites for High-Performance Mechanochromic Smart Membranes
Haomin Chen, Donghwi Cho, Kwonhwan Ko, Caiyan Qin, Minsoo P. Kim, Heng Zhang, Jeng‐Hun Lee, Eun Young Kim, Dawon Park, Xi Shen, Jinglei Yang, Hyunhyub Ko, Jung‐Wuk Hong, Jang‐Kyo Kim, Seokwoo Jeon
Abstract
Mechanochromic smart membranes capable of optical modulation have great potential in smart windows, artificial skins, and camouflage. However, the realization of high-contrast optical modulation based on light scattering activated at a low strain remains challenging. Here, we present a strategy for designing mechanochromic scattering membranes by introducing a Young's modulus mismatch between the two interdigitated polydimethylsiloxane phases with weak interfaces in a periodic three-dimensional (3D) structure. The refractive index-matched interfaces of the nanocomposite provide a high optical transparency of 93%. Experimental and computational studies reveal that the 3D heterogeneity facilitates the generation of numerous nanoscale debonds or "nanogaps" at the modulus-mismatching interfaces, enabling incident light scattering under tension. The heterogeneous scatterer delivers both a high transmittance contrast of >50% achieved at 15% strain and a maximum contrast of 82%. When used as a smart window, the membrane demonstrates effective diffusion of transmitting sunlight, leading to moderate indoor illumination by eliminating extremely bright or dark spots. At the other extreme, such a 3D heterogeneous design with strongly bonded interfaces can enhance the coloration sensitivity of mechanophore-dyed nanocomposites. This work presents insights into the design principles of advanced mechanochromic smart membranes.