All living organisms exist in a world affected by many external influences, especially water and light. Photonic nanostructures present in certain insects, have evolved over time in response to diverse environmental conditions, facilitating communication within and between species, camouflage, thermoregulation, hydration, and more. Up to now, only a few insect species have been discovered whose elytron changes its color due to permeation of water (or its vapor) through cuticle. Here we report on a scarabaeid beetle Hoplia argentea remarkable in its ability to shift from green to brownish-red when exposed to water, demonstrating reversible changes. Here we show that elytron and scales form a complex and efficient micro/nano-optofluidic system. Water is channeled into the elytral lacunae, then transported internally to the petals of the scales, where it is wicked inside each scale, pushing the entrapped air out. Wicking is a very fast process, occurring during a few seconds. The advantage of this principle is in extremely high pressure (approximately 15 bar) produced by capillary forces, which expediates permeation of air. We present optical models that explain the physical mechanisms behind the coloration, detailing how superhydrophilic properties influence optical behavior. Species within the genus Hoplia exhibit diverse coloration strategies, likely linked to their specific ecological niches. These organisms have evolved intricate optical and microfluidic systems that facilitate rapid alterations in body coloration, potentially serving purposes such as environmental camouflage and thermoregulation. Studying microfluidic and optical properties of the elytra will not only enhance our understanding of the biological purposes behind color change but also inspires design of artificial biomimetic devices. Dynamic fluid flow patterns, described in this paper, are fairly constant and unique and can be used in security applications as a, so called, physically unclonable functions (PUF). More broadly, this kind of microfluidic system can be used for controlled drug release, sensing, hydraulic and pneumatic pumping.

中文翻译：

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Hoplia sp. 甲虫的微流体和光学特性之间的复杂相互作用


所有生物体都存在于一个受许多外部影响的世界中，尤其是水和光。存在于某些昆虫中的光子纳米结构随着时间的推移而进化，以响应不同的环境条件，促进物种内部和物种之间的交流、伪装、体温调节、水合作用等。到目前为止，只有少数昆虫物种被发现，其鞘翅由于水（或其蒸气）通过角质层的渗透而改变颜色。在这里，我们报道了一种甲虫 Hoplia argentea，它在暴露于水中时能够从绿色转变为棕红色，表现出可逆的变化。在这里，我们展示了鞘翅和鳞片形成了一个复杂而高效的微/纳米光流体系统。水被引导到鞘翅腔隙中，然后在内部输送到鳞片的花瓣中，在每个鳞片内部被侵蚀，将滞留的空气推出。芯吸是一个非常快速的过程，在几秒钟内发生。该原理的优点是在毛细管力产生的极高压力（约 15 bar）下，这加快了空气的渗透。我们提供了解释着色背后的物理机制的光学模型，详细介绍了超亲水特性如何影响光学行为。Hoplia 属中的物种表现出不同的着色策略，可能与它们特定的生态位有关。这些生物已经进化出复杂的光学和微流体系统，有助于身体颜色的快速改变，可能用于环境伪装和体温调节等目的。 研究鞘翅的微流体和光学特性不仅会增强我们对颜色变化背后的生物学目的的理解，还会激发人工仿生装置的设计。本文中描述的动态流体流动模式相当恒定且独特，可以作为所谓的物理不可克隆函数 （PUF） 在安全应用中使用。更广泛地说，这种微流体系统可用于控制药物释放、传感、液压和气动泵送。