Rc08sma f01

The angle‐resolved optical response of the films was measured by optical spectroscopy on a custom goniometer setup. A broadband xenon lamp (HPX2000, Ocean Optics) was coupled to a reflective collimator (RC08SMA‐F01, Thorlabs) via a 100 µm optic fiber (FC‐UV100‐2, Avantes) and used to illuminate the sample with a spot diameter Ø ≈1 mm. The reflected light was collected using another collimator coupled to a UV–vis spectrometer (AvaSpec‐HS2048, Avantes) via a 1000 µm optic fiber (FC‐UV1000‐2, Avantes). The recorded light intensity was normalized to a white Lambertian diffuser and the exposure time was adjusted automatically using a high dynamic range method. Three goniometer measurement modes were used, as illustrated in Figure S18, Supporting Information. For specular measurements, the angles of illumination and collection (relative to the sample axis) were increased symmetrically about the sample axis, producing the scans shown in Figure S19, Supporting Information. For off‐specular measurements, the sample was illuminated at a fixed angle of 30° to the sample axis while the collection angle was varied, producing the scans shown in Figure S20, Supporting Information. For Supplementary Videos 1‐3, the respective blue, green and red bilayer films were rotated while the illumination and collection angles were kept fixed.

Angular resolved spectra were taken using a custom-built goniometer set-up [29 (link)]. Samples were prepared by cutting out a piece of roughly 1 cm² out of the agar. This piece was subsequently attached to a microscope slide with double-sided tape. The slide containing the bacteria on agar was then mounted on a rotating stage, and illuminated using light in the UV–VIS region (Ocean Optics HPX-2000 xenon lamp) that was collimated through an optical fibre that was attached to a reflective collimator (Thorlabs RC08SMA-F01). This resulted in an illuminating light beam with a spot size of 5 mm diameter. The angle of incidence of this light could be varied by rotating the sample. Light that was reflected and scattered from the sample was collected using the same fibre–collimator combination as used for the incident beam. The fibre was subsequently connected to a spectrometer (AvaSpec-HS2048, Avantes). The detection fibre and collimator were mounted on a rotating arm so that the angle of detection could be varied. At the detection angle, which equals the negative of the incident angle, no signal was collected due to a limitation in the set-up. All the spectra reported here were normalized against a white diffuser (labsphere SRS-99-010) at 0° incident and 5° collection angle.