Hierarchical PDMS-Based Metamaterial for Simultaneous Control of Visible, NIR and LWIR Wavebands

As carbon emissions increase and global warming becomes more serious, the concept of zero energy building (ZEB) has emerged, which covers the heating and cooling loads and other energy consumption of buildings with renewable energy such as photovoltaic. Achieving ZEB requires either increasing the building's own energy production or reducing energy loss. In particular, since energy loss is transferred in the form of heat, conduction/convection losses can be controlled by using highly insulated materials or phase change materials, but radiative energy loss which is the form of the electromagnetic wave is difficult to control. Thermal energy radiated from the building to the outside environment and solar energy incident to the building increase the heating or cooling load of the building, resulting in higher energy consumption. Each energy is a form of the electromagnetic wave in the long-wavelength infrared (LWIR) and near-infrared (NIR) bands, and in the case of windows and exterior walls, additional control of the visible waveband is essential for light transmission or aesthetics of the building exterior. Herein, a hierarchical Polydimethylsiloxane (PDMS)-based metamaterial is proposed to simultaneously control three wavebands, which are visible, NIR, and LWIR. Solar irradiation and atmospheric emission spectra were considered to tailor optical properties for controlling incident and outgoing energy. Moreover, the material was designed by using COMSOL Multiphysics software and fabricated without a photolithography process. By measuring the transmittance of visible waveband, the reflectance of NIR waveband, and the emissivity of LWIR waveband according to the control characteristics required for each energy type, the waveband controllability of the proposed metamaterial was confirmed.