The brilliant coloration of North America’s eastern bluebird is not attributed to pigmentation but rather to networks of channels just a few nanometers in size incorporated into the feathers. These structures have been replicated in the laboratory for practical applications in batteries and water filtration systems.

When placed in an oily solution and heated, the polymer and the oil blend and form a network. Source: Fernández-Rico, C., et al. Nature Materials, (2023)

Transparent silicone rubber was placed in an oily solution and left it to swell for several days in an oven heated to 140° F (60° C). It was then cooled to reduce the solubility of the liquid and the rubber extracted from the oily solution. Microscopic analysis revealed network structures similar to those responsible for the coloration of bluebird feathers.

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“We are able to control and select the conditions in such a way that channels are formed during phase separation. We have succeeded in halting the procedure before the two phases merge with each other completely again,” explained the researchers. The channel-​like structure is very similar to that of the bird’s feathers, and the resulting material is several centimeters in size and remains scalable.

The avian-inspired material developed by researchers from the University of Fribourg (Switzerland), Cornell University and ETH Zurich (Switzerland) offers scope to improve battery performance. A solid electrolyte derived from the new material described in Nature Communications would eliminate physical contact between the electrodes while maintaining good ion transport through the battery. For water filters, the ratio of surface to volume increases dramatically when channel-like structures are used, enhancing the efficiency of contaminant removal and preventing premature degradation of the filter’s surface membrane.