Using Eastern Bluebird's Feather Structure, Researchers Replicate Material for Applications

Saturday - December 2 2023, 08:25 UTC - 11 months ago

ETH Zurich researchers at the Laboratory of Soft and Living Materials, led by former ETH Professor Eric Dufresne, have replicated the feather structure of the Eastern bluebird to create a material for applications such as batteries and water filters. This new material is created by a heat-induced phase separation process and has the potential to replace liquid electrolytes with solid electrolytes in batteries and enhance the removal of contaminants from water.

The Eastern bluebird is a species of bird native to eastern North America known for the bright blue plumage on its head and back. What makes this bird so special is that its famous blue hue is not the result of pigments but rather an outcome of the animal’s unique feather structure. Now, ETH Zurich researchers at the Laboratory of Soft and Living Materials, led by former ETH Professor Eric Dufresne, have managed to replicate the material in the laboratory to be used in applications such as batteries and water filters.

The researchers began their experiments using a translucent silicone rubber that can be stretched and distorted and immersing it in an oily solution that allowed it to swell for several days in an oven at 60 degrees Celsius. Once they had chilled the material, they used a microscope to compare its nanostructure to that of the bluebird’s feathers. They found similar network patterns that could not only produce a blue hue but could also activate many other properties. This is partially due to the intricate process used for developing the material.

"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," said lead author Carla Fernández Rico. The simplicity of the new material combined with its unique traits have drawn a lot of attention and interest from the physics community. Perhaps its most notable quality is that it is made of only two ingredients but exhibits a final structure that is very complex and controlled by the properties of its components.

"We have been approached by several theoretical groups that are proposing the use of physical models in order to understand the key physical principles of this new process and to predict its outcome," said Fernández Rico. The researchers' main focus for applications is batteries and water filters. In the first, the material could be used to replace liquid electrolytes with solid electrolytes taking advantage of the invention’s network structure of interconnected channels. In the second, the material could be used to enhance and optimize the removal of contaminants such as bacteria or other particles from water.

"However, the product is still a long way from being ready for market," said Fernández Rico. "While the rubbery material is cheap and easy to obtain, the oily phase is quite expensive. A less expensive pair of materials would be required here." The researchers are now exploring the options of working with natural polymers, such as cellulose or chitin, which are more eco-friendly as they don’t rely on petroleum and are also significantly cheaper. Although these materials are not yet functional, the scientists hope to find methods of increasing their efficiency and adaptability to make their new process more scalable.

The study is published in Nature Materials. Study abstract: Bicontinuous microstructures are essential to the function of diverse natural and synthetic systems. Their synthesis has been based on the physical principles of self-assembly, typically requiring large amounts of energy and time. Here, we describe a simple process for the formation of bicontinuous microstructured networks in a binary polymer blend, using a heat-induced phase separation process. Upon cooling, an intricate connected network of nano- and micropillares is produced, which can be scalably applied to various substrates and shows diverse optical and mechanical properties. The process promises to provide a versatile tool for the bottom-up production of multifunctional materials.