Colour is often not a static trait but can change over time either through biotic or abiotic factors. Humidity-dependent colour change can occur through either morphological change (e.g. to feather barbules in birds) or by the replacement of air by water causing a shift in refractive index, as seen in arthropod multi-layer cuticles or scales. The scaled springtail Lepidocyrtus cyaneus has scales that produce colour largely via thin film interference from their lamina. We observed a marked colour change from golden to violet/purple coloration in humid conditions. Light microscopy, micro-spectrophotometry, contact angle goniometry and optical modelling indicate that the formation of a thin film of water on top of the hydrophilic scales increases their laminar thin film thickness, causing a shift towards violet/purple colour. Evaporation of the water film causes the metallic golden colour to return. This constitutes a remarkably rapid colour change (in the order of seconds), only limited by the speed of water film condensation and evaporation, that may serve as inspiration for new dynamically coloured materials and sensors.

中文翻译：

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鳞片弹尾鱼中形成水膜，随湿度而发生快速且可逆的颜色变化。

颜色通常不是静态特征，而是可以通过生物或非生物因素随着时间而变化。湿度依赖性颜色变化可以通过形态变化（例如鸟类的羽小羽）或通过水替换空气导致折射率变化而发生，如节肢动物多层角质层或鳞片中所见。鳞片弹尾蓝鳞鱼的鳞片主要通过其叶片的薄膜干扰产生颜色。我们观察到在潮湿条件下颜色发生显着变化，从金色变为紫罗兰色/紫色。光学显微镜、显微分光光度法、接触角测角法和光学模型表明，亲水鳞片顶部水薄膜的形成增加了层状薄膜的厚度，导致颜色向紫色/紫色转变。水膜蒸发导致金属金色回归。这构成了非常快速的颜色变化（以秒为单位），仅受水膜冷凝和蒸发速度的限制，这可以作为新的动态着色材料和传感器的灵感。