Real Robotic Plant Roots 

One day, they could be used to monitor soil. Or your inner organs.

 

Rootpict

The plantoid, of which Dr Mazzolai plans to demonstrate a partial prototype on July 29th at a conference at the Natural History Museum in London, will have a central stem containing a reservoir of liquid plastic of a sort that can be frozen by ultraviolet light. Half a dozen cylindrical roots will branch off this stem, and the plastic will flow through these from the reservoir to the tip. As in a real root, the tip will be a specialized structure. Instead of being a cone containing a meristem (a cluster of proliferating cells that drives the root’s growth) it will be a cone containing a motor, a light-emitting diode and a battery. The motor will suck liquid plastic through the root and push it to the periphery of the cone. Once there, the liquid will be solidified by ultraviolet rays from the diode, extending the cylinder and forcing the cone farther into the soil. As in real life, the gentle but relentless pressure of the root’s growth should be enough to make it advance through the soil, fractions of a millimeter at a time. The researchers expect their prototypical robotic roots to be able to penetrate up to a meter of real soil.

A root system would be able to pull energy from the soil without relying on other power sources, such as batteries, solar or wind.

The direction of growth is controlled by a material known as an electro-rheological fluid, which is also stored in the cone. Such fluids become more viscous when an electric current is applied to them, and changing the viscosity on one side of a root but not the other, using current from the battery, causes the direction of growth to vary.
Check this video
http://www.youtube.com/watch?v=GALHb-b5060
One thing missing from the prototypes is a control system that responds to the root’s environment. The plan is to fit the next generation of cones with sensors that look for whatever the root is designed to find, and control its growth accordingly. Writing the software for these sensors may illuminate how real roots work. According to Dr Mazzolai, the first person to ask about that was Charles Darwin. He could not come up with an answer, and 130 years later no one else has either.

From the print edition: Science and technology