Cactus roots inspire creation of water-retaining material

Like all living things, cacti need water to survive. Yet they thrive in some of the world's driest places. The key is the plant's shallow, but extensive root system that quickly soaks up rainfall, which seldom penetrates more than just a few inches into the soil. During droughts, the roots dehydrate and shrink, creating air gaps that prevent water from escaping back into the soil. Intrigued by these traits, Sang Joon Lee, Hyejeong Kim and Junho Kim wanted to create a durable material that could effectively absorb and store water, without changing other physical properties.

The research team sought to replicate the key features of the cactus root system. To imitate the cactus root and its outer covering, they made a material composed of cellulose fibers, agarose cyrogel and microparticles. Then, they made a cylindrical-shaped gel and freeze-dried it to form a structure that mimics the layered composition of cactus root epidermis. Laboratory tests suggest that the resulting cactus-root-inspired material (CRIM) is capable of absorbing water nearly 930 times faster than it loses through evaporation. The researchers say the mixture of cellulose fibers, microparticles and cryogel is adjustable for particular needs. For example, adding water-repellant microparticles to this system could produce CRIMs useful in oil separation and other oil-based engineering processes. They conclude that CRIMs could eventually have a host of applications in agriculture, cosmetics and medicine.