Researchers Create First Soft Robot Mimicking Plant Tendrils

The world’s first soft robot that imitates plant tendrils has been developed by researchers at IIT-Istituto Italiano di Tecnologia. The robot uses the same physical principles that establish water transport in plants to climb and curl.

Barbara Mazzolai headed the research team, and the study results have been reported in Nature Communications. The tendril-like soft robot may lead to the development of soft braces and other similar wearable devices in the future, and would be able to actively change their shape.

In 2015, RoboHub listed Barbara Mazzolai among the 25 most influential women in robotics. Mazzolai also coordinated the EU-funded project called “Plantoid” earlier in 2012, which introduced the first plant robot to the world. The research team, which includes Indrek Must and Edoardo Sinibaldi, is a small yet well-assorted group, based on complementary backgrounds— Mazzolai a biologist and has done PhD in microsystems engineering, Sinibaldi is an aerospace engineer and holds a PhD in applied mathematics, and Must is a materials technologist and has done PhD in engineering and technology.

Plants and their movement inspired these researchers. Obviously, plants cannot escape like animals; therefore, they have related their movement to growth and in doing so, they constantly adapt their morphology according to the external conditions. Even the organs of the plants exposed to the air are capable of carrying out intricate movements like, for instance, the closing of leaves in carnivorous plants or even the development of tendrils in climbing plants, which are capable of coiling around external supports, and uncoiling if the supports are insufficient, to prefer the growth of the plant itself.

The scientists initially examined the natural mechanisms through which plants leverage water transport within their organs, cells, and tissues to move, and subsequently simulated it in an artificial tendril. “Osmosis”—the hydraulic principle—is based on the presence of tiny particles in the intracellular plant fluid called the cytosol.

The researchers initially used a basic mathematical model to understand how large a soft robot— fueled by the above-mentioned hydraulic principle— should be, so as to prevent relatively slow movements. Next, they gave the shape of a small tendril to the robot and gained the ability to perform reversible movements, just like how the real plants actually do.

The researchers created the soft robot from a stretchable PET tube, comprising of a liquid with electrically charged particles, or ions. When a 1.3 V battery is used, the particles are attracted and immobilized on the flexible electrodes’ surface at the base of the tendril; the movement of these particles causes the liquid to move, whence that one of the soft robot. To go back, the electric wires can be simply disconnected from the battery and joined together.

For the first time, the potential of controlling osmosis to stimulate reversible movements has been shown. In addition, the effective use of flexible fabrics and a standard battery indicates the possibility of developing soft robots that can be conventionally adapted to the surrounding environment, thus offering the potential for safe and improved interactions with living beings or objects.

Promising applications of soft robots will span from the development of flexible robotic arms for exploration purposes to wearable technologies. The challenge of mimicking the ability of plants to move in unstructured and fluctuating environments has just started.

In this regard, Mazzolai and her team are working as coordinators in a latest project, called “GrowBot,” which is supported by the European Commission under the FET Proactive program. The project envisions the development of a robot that will have the ability to control its adaptation and growth to the surrounding environment with the potential to detect the surfaces to which it anchors, or the supports to which it attaches, similar to how the real climbing plants do.