Self-rolling of vanadium dioxide nanomembranes for enhanced multi-level solar modulation

Abstract

Thermochromic window develops as a competitive solution for carbon emissions due to comprehensive advantages of its passivity and effective utilization of energy. How to further enhance the solar modulation ($${\triangle T}_{{{{{{{\rm{sol}}}}}}}}$$ △ T sol ) of thermochromic windows while ensuring high luminous transmittance ($${T}_{{{{{{{\rm{lum}}}}}}}}$$ T lum ) becomes the latest challenge to touch the limit of energy efficiency. Here, we show a smart window combining mechanochromism with thermochromism by self-rolling of vanadium dioxide (VO2) nanomembranes to enhance multi-level solar modulation. The mechanochromism is introduced by the temperature-controlled regulation of curvature of rolled-up smart window, which benefits from effective strain adjustment in VO2 nanomembranes upon the phase transition. Under geometry design and optimization, the rolled-up smart window with high $${\triangle T}_{{{{\rm{sol}}}}}$$ △ T sol and $${T}_{{{{{{\rm{lum}}}}}}}$$ T lum is achieved for the modulation of indoor temperature self-adapted to seasons and climate. Furthermore, such rolled-up smart window enables high infrared reflectance after triggered phase transition and acts as a smart lens protective cover for strong radiation. This work supports the feasibility of self-rolling technology in smart windows and lens protection, which promises broad interest and practical applications of self-adapting devices and systems for smart building, intelligent sensors and actuators with the perspective of energy efficiency.

Mechanically-Guided 3D Assembly for Architected Flexible Electronics

“…In this review, responsive materials denote materials that response to different types of physical (e.g., heating, illumination) 16,17,109,117,118,162,163 and chemical (e.g., redox reactions) stimuli. 119,123,158 The residual-stress-induced rolling assembly is typically accomplished through releases of heteroepitaxial crystalline bilayers 91,92,136,137 (Figure 2a), prestressed nonepitaxial nanomembranes 108,162,163 (Figure 2b), and other layered heterogeneous structures. 94 Figure 2a illustrates the rolling of a typical heteroepitaxial bilayer crystalline film (consisting of materials 1 and 2 with different sets of lattice constants a 1 and a 2 ) by the use of photoresist as the sacrificial layer.…”

“…Mechanically-guided 3D assembly methods exploit controlled mechanical deformations to transform planar electronic devices into 3D ones with various geometric configurations. Based on loading schemes and deformation characteristics, mechanically-guided 3D assembly methods are classified into rolling assembly, − ,− ,,,− ,,,,− folding assembly, − ,− ,,,,− curving-induced assembly, ,− ,,,,− …”

“…Based on the mechanisms to generate strain mismatches, rolling assembly approaches are divided into two different subfamilies, i.e., residual-stress-induced rolling assembly and responsive-material-induced rolling assembly (Figure a–c). In this review, responsive materials denote materials that response to different types of physical (e.g., heating, illumination) ,,,,,, and chemical (e.g., redox reactions) stimuli. ,, …”

“…The residual-stress-induced rolling assembly is typically accomplished through releases of heteroepitaxial crystalline bilayers ,,, (Figure a), prestressed nonepitaxial nanomembranes ,, (Figure b), and other layered heterogeneous structures Figure a illustrates the rolling of a typical heteroepitaxial bilayer crystalline film (consisting of materials 1 and 2 with different sets of lattice constants a 1 and a 2 ) by the use of photoresist as the sacrificial layer.…”

“…The second class of rolling assembly approaches mainly leverage engineered stress gradients created by the utility of specific characteristics of various stimuli-responsive materials, such as actuation of smart materials (e.g., hydrogels, liquid crystal elastomers, shape memory polymers/alloys), ,− varied thermal expansion coefficients, material phase transitions, ,, among others . Hydrogel-based composites are capable of forming complex 3D configurations (Figure g) by swelling-driven rolling assembly .…”