Researchers have created a synthetic "tree" - a centimeter-sized hydrogel with nanopores that can pull water just like real trees pull moisture up their tall trunks.
Optical micrograph image of a synthetic tree. Credit: Tobias Wheeler.The scientists, led by Abraham Stroock of Cornell University, explained that this process is called "transpiration." Getting water to overcome the force of gravity and move upward to the top of a tree requires a lot of energy. It's also a large factor in determining the maximum height of a tree - after it reaches a certain height, it just can't pull water any higher.
By simulating transpiration in the lab, the researchers show that the process is purely physical, and requires no biological energy. Understanding how the process works could allow researchers to use it for several human applications.
In nature, real trees have long strands of transport tissue in their wood called xylum. When water evaporates from the upper leaves of the tree into the atmosphere, the xylum experiences a negative pressure, and this tension pulls water from the roots to the upper parts of the tree. In a sense the xylum is like a long straw, through which water is sucked to the top.
The Cornell researchers mimicked this behavior by using laboratory materials. They fabricated leaf and root membranes from hydrogel, similar to the material used in soft contact lenses. Then they created tiny xylem capillaries in nanopores in the hydrogel using microfabrication techniques, through which water could be pulled.
The researchers are investigating several applications for the water-pulling technique. One idea is to develop a new kind of passive heat-transfer technology to heat buildings. For instance, a solar collector on the roof could heat a fluid, which could be distributed by gravity to lower parts of the building. Then the fluid could be recycled back up to the roof using the transpiration technique.
The method could also be used for cooling laptops and de-contaminating the soil, where contaminated fluid could simply be sucked out of the soil. Another idea is using the method to draw water out of deep soil, doing away with the need to dig wells.
via: Cornell University