Journal: Nature Communications

Article Title: Anderson light localization in biological nanostructures of native silk

doi: 10.1038/s41467-017-02500-5

Figure Lengend Snippet: Self-cooling function of native silk revealed by biogenic light localization. a Top: measured steady-state temperature of native silk, a conventional reflecting material (i.e. aluminium) and a high-emissive material (i.e. carbon black paint-coated aluminium) under direct sunlight exceeding 1000 W m −2 (grey line) on a clear day of late summer in West Lafayette, Indiana. The temperature is measured at the centre immediately below the back surface of each cooling panel. Bottom: computed steady-state temperature using a 3D multiphysics model of heat transfer (Methods). b 3D illustration of the scalable biophotonic cooling device, continuously integrating unit silk patches with a diameter of 10 mm. Photograph of the device is shown in Supplementary Fig. . c Computed temperature distributions below the silk (left) and the aluminium (right) cooling panels at the solar irradiance of 1000 W m −2 (2 p.m. local time). d Ensemble-averaged reflectance in the visible/NIR region and emissivity in the IR region from the inner/outer compartments of an white silk cocoon with a thickness of ~400 µm (blue solid lines). For the entire solid angle Ω collection, two hemispherical measurement systems are used for the visible/NIR (Thorlabs IS200-4) and IR (Surface Optics SOC-100 HDR) regions. After loss compensation for the limited NA of a Fourier transform infra-red (FTIR) microscope , FTIR microscopy measurements (blue dotted line) further provide enhanced visibility of the vibrational modes of silk protein marked with ○ and Δ; sample thickness ~100 µm. In the list of vibrational modes, the label prefixes δ , γ and ν indicate bending, rocking and stretching vibrations. The suffixes as and s imply asymmetric and symmetric modes. e Real and imaginary parts Re(n) (top) and Im(n) (bottom) of the complex refractive index of a regenerated silk film in the entire visible/NIR/IR regions. Amide bond links amino acid monomers in fibroin protein (i) and has five vibrational modes within the wavelength of interest (ii). In spite of the identical protein composition, the colour and scattering of silk drastically change if native silk (iii) loses the light localization structure to form the regenerated film (iv)

Article Snippet: Using RF Module of COMSOL Multiphysics (4.3a version), we computed all of the modes near λ 0 = 600 nm for each disordered system and displayed the norm of E z field component of the transverse magnetic mode.

Techniques: Microscopy, Refractive Index