Just like a real plant, Plantoid has branches and leaves. [Credit Italian Institute of Technology]

The Day of the Plantoid Robots

The robots we’re familiar with seeing are usually humanoid or animal-inspired – think Asimo or Aibo - but what can robots based on plants offer us?

Intelligent plants anyone? Perhaps John Wyndham’s The Day of the Triffids springs to mind, with its hordes of 7ft-tall marauding, venomous, carnivorous plants capable of locomotion and communication? Or are you thinking more M Night Shyamalan’s plant-based film caper The Happening, where a group of survivors attempts to out-run an airborne, mass suicide-inducing neurotoxin, emitted by ‘nature’ to protect itself against danger? I fail to see how a stressed-out Mark Wahlberg constitutes a threat to the East Coast of America’s indigenous tree population, but there you go…

Move over Treebeard

Well, plant intelligence is entering a new phase thanks to Dr Barbara Mazzolai, coordinator of the Centre for Micro-BioRobotics (CMBR) at the Italian Institute of Technology, who has been taking inspiration from plant behaviour and applying it to the world of robotics. With a focus on bioinspired soft robotics – looked at more widely in the E&T article Soft robots: merging nature and the future – Dr Mazzolai and her team are working on an EU-based project designing and developing new robotic solutions and advanced components, taking their inspiration from nature.

It can be deemed controversial to use the term ‘intelligence’ in conjunction with plants, but in looking at the way plants are aware of their environment, adapt, communicate and move it’s easy to assign intelligence to their behaviour. However, whether or not this demonstrates sentient decision-making over sophisticated adaptation, there seems to be a consensus on one thing – that we have seriously underestimated their incredibly complex biology.

Dr Mazzolai aims to develop new bioinspired technologies and robotic solutions, increasing our knowledge of the biological system used as models. Commenting on the project, she said: “Many robots are inspired by animals, but people never thought about plants as a model, because usually they are considered quite passive organisms - not able to move or communicate. When I started, people looked at me strangely, but then I showed people the movements in plants, that they are able to sense the changing condition of the environment. When I demonstrated that it is possible to transform these features into something that can move artificially, the story changed completely.”

Smart technology

The plant kingdom represents an incredible source of inspiration for smart technological solutions, such as new materials, mechanisms, sensors, actuators and control schemes. Plants are dynamic and highly sensitive organisms, harnessing efficient soil exploration with the ability to occupy almost any surface on the planet.

In order to exploit dispersed environmental resources, plants develop a network of growing and branching roots, whose tips are highly sensorised and efficiently explore the soil volume, mining for minerals and taking up water to meet their primary functions.

Development of novel principles for penetration, sensory detection, and autonomous decision making could open up new horizons in robotics: autonomous agents able to localise a subsoil source could be used in order to find water and other relevant substances, or to detect the presence of dangerous pollutants and minimise soil contamination.

In studying such plant capabilities, CMBR has developed a robot inspired by plant roots, called Plantoid, investigating the smart strategies of plant roots in performing soil exploration, in order to develop a new generation of technologies in sensing, actuation and collective behaviour.

How does your robot grow?

Plantoid has a trunk like a real plant, with branches and leaves, and several artificial roots that are able to grow through additional material, mimicking how plants function. Dr Mazzolai adds, “The artificial root can move in narrow spaces. It can autonomously look for oxygen or water or the presence of life.”

As it grows, layers of new materials (in the form of a polypropylene filament) are deposited adjacent to the tip of the device, in order to produce a motive force at the tip and a hollow tubular structure extending to the surface of the soil. The addition of material at the tip reduces friction to almost zero, favouring the penetration into the soil at low energy consumption.

As Dr Mazzolai explains: “To a great extent, a robot can be defined as an autonomous device which has a well-defined structure not able to change or to grow. Taking inspiration from the growth mechanism of natural roots, we had the ambition of designing a robot able to grow, a brand new approach in the robotic field.”

Future Plantoids

Robots developed along such lines could be used in applications as diverse as environmental monitoring, space applications or for rescue under debris because they can adapt to the environment around them like a natural system. The robot doesn't have a predefined structure, but can create on the basis of need, growing through and around structures or obstacles.

The team at CMBR are working in a field that promises a new generation of technologies, with the potential to be used in many different activities such as soil monitoring, exploration on contaminated areas or mineral deposits – whether on earth or other planets – and medical and surgical applications, like new flexible endoscopes, able to steer and grow in delicate human organs without damaging them.

Talking about the next stage of the project, Dr Mazzolai said: “The next steps will be focused on the integration of the identified functions into a single robotic root that embeds sensors, actuators, control units, an elongation/growing zone and a bending area. The robot roots will be able to penetrate and steer in the soil, guided by gravity or the proximity of water or other chemicals.

“On the engineering side, our goal is to develop new flexible plant-inspired robots able to grow by adding new materials. This will require the development or use of new flexible sensors based on soft materials, as well as distributed control and robotic architectures. One interesting topic for study is plant structures that exploit external environmental energy to move or implement efficient motion strategies.”

And then there’s the thorny question of intelligence. Dr Mazzolai intends to address the issue of intelligent behaviour by looking at a plant’s capability for adaptively variable growth and development during its lifetime and the potential for this in informing the development of smart devices, “not only with the ability to sense, but with the capability to follow stimuli and take decisions to accomplish the required tasks.”

The interdisciplinary study of plants, from a biological and an engineering approach, promises the design and production of new devices that will impact positively on our quality of life and on the environment. As Dr Mazzolai adds: “Plants are underestimated. They move under the soil and it's difficult to understand the behaviour of these systems, but they have features that can really help us understand nature.”


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