Figure 1: Schematic of biomimetic colourimetric sensor system.
(a) Turkeys autonomously change their red skin to white and/or blue when excited. The blue colour is associated with structural colourization of collagen nanostructures11, although their colour-change mechanism is not known with molecular detail. As a result, turkeys are known as ‘seven-faced birds’ in Korea and Japan. (b) A histological section of turkey skin stained with Masson’s trichrome shows that turkey skin consists mainly of collagen and highly vascularized tissues (scale bar, 50 μm). (c) Transmission electron micrograph of perpendicularly aligned collagen bundled fibres in the dermis (scale bar, 200 nm). (d) Bioinspired phage-based colourimetric sensors, termed Phage litmus, are composed of hierarchical bundles like the collagen fibres in turkey skins. Application of target molecules (chemical stimuli) causes colour shifts due to structural changes, such as bundle spacing (d1 and d2) and coherent scattering. Using a handheld device’s camera (iPhone) and home-built software (iColour Analyser), we can identify target molecules in a selective and sensitive manner.
