A Simple Way to Harvest the Energy of Water
By LIDA TUNESI
Water is the driver of life on Earth, and as a result many things in nature physically respond to it. In wet conditions, a pine cone will close its scales, preferring to release its seeds on a dry, sunny day. Tiny pores on leaf surfaces open and close in response to water entering and leaving the surrounding cells.
In imitation of these phenomena, researchers at the Advanced Science Research Center at The Graduate Center, CUNY, have designed a simple material that expands and contracts in response to water diffusing in and out. Their work was led by the labs of Professors Xi Chen and Rein Ulijn and appears in Nature Materials.
With further refinements, the material could be used to harvest the energy of water evaporation, and may also have applications in soft robotics and adaptive materials.
The material is a crystal, but not in the sense of colorful, decorative rocks. It’s made of repeating units of three different amino acids, which are the same molecules that make up proteins. The simplicity of this design is a plus, the authors say, as it makes the material biocompatible, cost-effective, and easy to study and modify.
The crystal has both tough and flexible areas, which lets it expand and contract. When humidity in the surrounding area is high, water diffuses into nanopores in the material. When the humidity drops, many of the water molecules evaporate back out.
“Evaporation energy then becomes mechanical energy, through interactions between water and the material, and the material contracts,” Chen explained.
Through their work, the researchers also gained insights into the mechanisms behind water-responsive phenomena in nature, which will help with future designs and improvement of materials.