Interdigitated Three-Dimensional Heterogeneous Nanocomposites for High-Performance Mechanochromic Smart Membranes

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 threedimensional (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 modulusmismatching 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.

Color‐Tuning Mechanism of Electrically Stretchable Photonic Organogels

“…Note that the electromechanical stretching of the photonic organogels was directly affected by the symmetrical expanding actuations of the DEA with the contraction of thickness. In recent studies where similar mechanochromic systems were investigated, [ 70,73,76,78,79 ] the organogels exhibited hexagonal lattice structures. However, in contrast to the uniaxial deformation of the HCP lattice observed in these studies, here, the HCP lattice structure of the electrically stretchable nano organogels with circular compliant facing electrodes was symmetrically expanded along both the horizontal and vertical directions during the color change process.…”

“…[2,43,[70][71][72] Nevertheless, the wavelengthtuning mechanism of such electrically stretchable organogels is not well understood yet. Although recent reports have comprehensively illustrated the uniaxial mechanical stretchinginduced color change mechanism of similar hydrogels, [73][74][75][76][77][78][79][80] a deeper understanding of electrically stretchable chromonic organogel systems, in comparison with mechanical stretching mechanochromic systems, is required. However, elucidating the electrical mechanochromic processes involved in electrically stretchable and variable nanostructures, presents notable technical challenges.…”

Soft Optomechanical Systems for Sensing, Modulation, and Actuation

“…Based on these effects, Chen et al reported periodic 3D structures composed of two interdigitated PDMS phases with different Young's modulus. Under strain, numerous nanogaps emerged between the phases acting as light scattering centers, rendering a high-contrast mechanical modulation of the light transmittance [149] (Figure 6d).…”

Solar and Thermal Radiation‐Modulation Materials for Building Applications

“…Transparent Components: Mechanochromic (MC) window, which is composed of mechanoresponsive optical materials, can switch its solar optical properties in response to mechanical strain. [18,92] The strain can reconfigure the surface morphologies or deform internal structures of the mechanoresponsive materials, which would tune the solar scattering/reflecting characteristics of the materials, resulting in varied solar transmittance. Based on the working principle, three categories of MC windows are reviewed in this section, that is, wrinkling-based, delamination bucklingbased, and kirigami structure-based.…”