Large-area, self-healing block copolymer membranes for energy conversion.

Membranes are widely used for separation processes in applications such as water desalination, batteries and dialysis, and are crucial in key sectors of our economy and society1. The majority of technologically exploited membranes are based on solid polymers and function as passive barriers, whose transport characteristics are governed by their chemical composition and nanostructure. Although such membranes are ubiquitous, it has proved challenging to maximize selectivity and permeability independently, leading to trade-offs between these pertinent characteristics2. Self-assembled biological membranes, in which barrier and transport functions are decoupled3,4, provide the inspiration to address this problem5,6. Here we introduce a self-assembly strategy that uses the interface of an aqueous two-phase system to template and stabilize molecularly thin (approximately 35 nm) biomimetic block copolymer bilayers of scalable area that can exceed 10 cm2 without defects. These membranes are self-healing, and their barrier function against the passage of ions (specific resistance of approximately 1 MΩ cm2) approaches that of phospholipid membranes. The fluidity of these membranes enables straightforward functionalization with molecular carriers that shuttle potassium ions down a concentration gradient with exquisite selectivity over sodium ions. This ion selectivity enables the generation of electric power from equimolar solutions of NaCl and KCl in devices that mimic the electric organ of electric rays.

Thin film structural color is widespread in slime molds (Myxomycetes, Amoebozoa).

Brilliant colors in nature arise from the interference of light with periodic nanostructures resulting in structural color. While such biological photonic structures have long attracted interest in insects and plants, they are little known in other groups of organisms. Unexpected in the kingdom of Amoebozoa, which assembles unicellular organisms, structural colors were observed in myxomycetes, an evolutionary group of amoebae forming macroscopic, fungal-like structures. Previous work related the sparkling appearance of Diachea leucopodia to thin film interference. Using optical and ultrastructural characterization, we here investigated the occurrence of structural color across 22 species representing two major evolutionary clades of myxomycetes including 14 genera. All investigated species showed thin film interference at the peridium, producing colors with hues distributed throughout the visible range that were altered by pigmentary absorption. A white reflective layer of densely packed calcium-rich shells is observed in a compound peridium in Metatrichia vesparium, whose formation and function are still unknown. These results raise interesting questions on the biological relevance of thin film structural colors in myxomycetes, suggesting they may be a by-product of their reproductive cycle.

Anoplophora graafi longhorn beetle coloration is due to disordered diamond-like packed spheres.

While artificial photonic materials are typically highly ordered, photonic structures in many species of birds and insects do not possess a long-range order. Studying their order-disorder interplay sheds light on the origin of the photonic band gap. Here, we investigated the scale morphology of the Anoplophora graafi longhorn beetle. Combining small-angle X-ray scattering and slice-and-view FIB-SEM tomography with molecular dynamics and optical simulations, we characterised the chitin sphere assemblies within blue and green A. graafi scales. The low volume fraction of spheres and the number of their nearest neighbours are incompatible with any known close-packed sphere morphology. A short-range diamond lattice with long-range disorder best describes the sphere assembly, which will inspire the development of new colloid-based photonic materials.