WHY does ivy stick so well to walls? It was a question that puzzled Charles Darwin, but only now have researchers cracked the problem. It turns out the plant uses nanotechnology.
Ivy stems grow disc-shaped rootlets which secrete a yellowish substance. A team led by Mingjun Zhang at the University of Tennessee in Knoxville has done the first in-depth analysis of these secretions and discovered that it is a gel containing globules about 70 nanometres across that seems to supply the sticking power.
When Zhang鈥檚 team ran the nanoparticles through chemical tests they found 19 primary compounds, most of which seem to be 鈥減olar鈥� molecules (Nano Letters, ). Opposite ends of polar molecules have opposing electric charge, and this enhances their ability to link with other molecules through hydrogen bonds. Although these bonds are relatively weak, 鈥渁dding up millions or billions of weak adhesion could be a big force鈥�, Zhang says. 鈥淭hat is what ivy is doing.鈥�
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The researchers are now investigating the possibility of developing a paint to protect walls from damage caused by climbing ivy. They are also looking into engineering the ivy to produce custom nanoparticles, as a route to 鈥済reen manufacturing鈥�, says Zhang.
