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The amniotic egg fulfils a critical role in reproduction by serving as an interface between the external environment and the embryo. Because non-avian reptiles are rarely incubated, they must be heated by, and absorb water from, the oviposition site for the developing embryo. The mechanisms by which they absorb sufficient, but not excess, water and how these mechanisms vary with local habitat is largely unknown, despite its significance to their evolution. Here, we first performed histology, Fourier-transform infrared spectroscopy and dynamic vapor sorption experiments to elucidate the mechanisms of eggshell absorption for 56 reptile species. Then, we used phylogenetic comparative analysis to test the hypothesis that the absorptive capacity of reptile eggshells increases with aridity of the environment. We found that water absorption increases in the presence of a superficial mucopolysaccharide layer and decreases with increased calcium content. We found that eggs from arid environments have highly absorbent eggshells, but only in species with weakly calcified shells. Our results suggest that reptile eggshells have over evolutionary time tuned absorptive capacity to environmental moisture level. Since these eggs often must sustain conflicting constraints, they may serve as inspirations for new biomimetic materials, such as water filtering membranes or humidity sensors. [ABSTRACT FROM AUTHOR]

Colorimetric sensors for monitoring and visual reporting of acidic environments both in water and air are highly valuable in various fields, such as safety and technical textiles. Until now sol-gel-based colorimetric sensors are usually nonflexible bulk glass or thin-film sensors. Large-area, flexible sensors usable in strong acidic environments are not available. Therefore, in this study organically modified silicon oxide nanofibrous membranes are produced by combining electrospinning and sol-gel technology. Two pH-indicator dyes are immobilized in the nanofibrous membranes: methyl yellow via doping, methyl red via both doping, and covalent bonding. This resulted in sensor materials with a fast response time and high sensitivity for pH-change in water. The covalent bond between dye and the sol-gel network showed to be essential to obtain a reusable pH-sensor in aqueous environment. Also a high sensitivity is obtained for sensing of HCl and NH3 vapors, including a memory function allowing visual read-out up to 20 min after exposure. These fast and reversible, large-area flexible nanofibrous colorimetric sensors are highly interesting for use in multiple applications such as protective clothing and equipment. Moreover, the sensitivity to biogenic amines is demonstrated, offering potential for control and monitoring of food quality. [ABSTRACT FROM AUTHOR]

A false‐colored SEM image illustrates color changing nanofibrous silicon oxide membranes. On page 5987, R. Hoogenboom, K. De Buysser, K. De Clerck, and co‐workers report synthesis of such membranes through dye functionalization and electrospinning of silane precursors. These flexible, reusable sensors with fast response time and high sensitivity change color upon contact with acids in water or air. They are highly valuable for safety applications, protective clothing, and equipment. [ABSTRACT FROM AUTHOR]