Fig. 3: Polymer-based micro-photonic multi-function metamaterials (PMMM) working principle, radiative cooling performance and light diffusion.
a Simulated ray propagation maps of the PMMM for θin = 0°, 40°, and 80° in the visible range. Most of the incident light (>80%) diffuses in the range of ±30° when θin = 0°. The micro-pyramid structures can successfully redirect the incident sunlight to the down direction when the incident angle is as high as θin = 80°. b SEM images of PMMM samples with different sizes of the micro-pyramids. There are ~1 to 1.5 μm spaces between the micro-pyramids. c Measured global transmittance (τg_ave) and emissivity (εave) of for PMMM with different pyramid sizes. d Comparison of the global transmittance (0.3–2.5 μm) and emissivity (8–13 μm) of the PMMM (10-μm pyramid with glass substrate) in this study and transparent/translucent radiative cooling materials in the literature. The PMMM in this study exhibits both higher transmittance and also higher emissivity than other emerging transparent/translucent radiative cooing materials. The inserted photograph shows the flexible PMMM film. e Simulated radiative cooling power of PMMM (10-μm-pyramid with glass substrate) and glass when heat convection coefficient with the ambient is h = 5 W/m2/K (Ta = 25 °C). f Simulated radiative cooling power of PMMM (10-μm-pyramid with glass substrate) and glass when h = 10 W/m2/K (Ta = 25 °C). g The Photosynthesis rate of tomato plants as a function of diffused light percentage, and the estimated improvement of photosynthesis rate by the PMMM. The PMMM is calculated and estimated to be able to improve the photosynthesis rate by ~9% compared to normal glass. The data of the photosynthesis rate as a function of the diffuse light percentage is referred to experimental results in ref. 61. Source data are provided as a Source Data file.
