The bold blue hue of the Eastern bluebird is a result of the unique microscopic structures found on its feathers. Researchers at ETH Zurich have now imitated this structure to make a material that could one day make better batteries and water filters.
Under the microscope, the bluebird’s wing feathers show a network of channels that have diameters about a thousandth the width of human hair. Light bounces around in these channels in a way that produces a bright blue.
But the unique structure of interconnected channels, which create a huge surface area, are useful for certain applications. Such porous nanostructured materials could, for instance, be used to make battery electrodes that store a lot of energy and could be charged faster, and more effective filters for removing bacteria or chemical contaminants from water.
New 3D printing methods could be used to create such intricate microscopic structures. But those methods are complex, costly, and time-consuming. This limits the size of the final material they can produce.
Materials scientist Eric Dufresne and colleagues came up with a simple, one-step process instead. They start by putting transparent silicone rubber into an oily solution, and heating it to a temperature of 60°C, which mixes the two otherwise immiscible materials.
The rubber swells over a period of a few days. Then the team cooled the material, which separates the rubber from the oil, resulting in the formation of a microscopic network of channels. The channels were much like those found in bluebird feathers, only four times wider.
The simple process and the use of only two ingredients should allow large-scale production of such nature-inspired materials, the researchers write in a paper published in Nature Materials.
They are now exploring the use of natural polymers such as cellulose to make similar materials that are more sustainable and are significantly cheaper.
Source: Carla Fernández-Rico et al. Elastic microphase separation produces robust bicontinuous materials. Nature Materials, 2023.