Robotic Plant

Barbara Mazzolai
Italian Institute of Technology in Genoa

Plants could soon have robotic counterparts. Barbara Mazzolai from the Italian Institute of Technology and colleagues are creating a system that mimics the behaviour of roots. The team plans to use bespoke soft sensors for underground exploration, tips that grow by unwinding material and a mechanism to reduce friction when penetrating the soil. The artificial system will be equipped to detect gravity, water, temperature, touch, pH, nitrate and phosphate.

Researchers working on the Plantoid project, led by Barbara Mazzolai of the Italian Institute of Technology, in Pontedera, hope to develop robot plant roots that will be as good as the real things, if not better. In doing so, they seek to understand how real roots work and also to devise machines that might monitor soil pollution, prospect for minerals and look for water.

Modelling a growing root is complex because it bends while increasing in length, adding cells on the opposite side from the direction in which it is heading. At the same time, a root perceives several physical and chemical stimuli at once and prioritises them; how it makes these decisions is not completely understood. “The mock-ups and prototypes we’ve developed aim to validate some of the functions and features of plant roots,” says Mazzolai.

In addition to mimicking a single root, the team is also looking at how roots interact with each other, coordinating their movements through soil. “New findings could be the basis for novel swarm intelligence,” says Mazzolai.

The system could produce more energy-efficient robots that can adapt to their environment. An obvious use for plant-like robots is environmental monitoring in soil, but their knack for exploration and ability to anchor themselves could have applications in space.

They also have potential uses in medicine, for example as flexible, growing endoscopes that can move easily inside a human body. “The ability to bend, grow at low pressure and with low friction while adapting to the surrounding environment could offer a new vision for medical tools,” says Mazzolai.

Robotic roots could be used to monitor changes in the soil, with sensors to measure nitrate, pH, water, temperature, and even gravity. Creator Barbara Mazzolai says they could also be used as a medical device. “The ability to bend, grow at low pressure and with low friction while adapting to the surrounding environment could offer a new vision for medical tools,” she told New Scientist. Imagine vaguely tentacle shaped sensors growing inside you during surgery.

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 specialised 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 millimetre at a time. The researchers expect their prototypical robotic roots to be able to penetrate up to a metre of real soil.

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.

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.


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