FiloBot can grow by 3D-printing itself and use real plants as support. Credit: Istituto Italiano di Tecnologia (IIT).
Researchers at the Italian Institute of Technology (IIT) have developed a growing robot, named FiloBot, that responds to gravity and light by autonomously adopting some of the behaviors of climbing plants1. The study, published in Science Robotics, is the culmination of a 10-year project for Barbara Mazzolai’s group, which, inspired by plants roots, used additive manufacturing, or 3D printing, to mimic the growth of climbing plants.
“Climbing plants grow against gravity and exploit supports to win the competition for light and other resources, in challenging and crowded environments such as tropical forests,” explains Mazzolai. “They can use tendrils and hooks, or twine to the support itself, and FiloBot exploits this latter strategy.”
Such robots could be able to navigate unstructured environments and cross voids, skills that are harder to emulate for robots with wheels or legs. They could support search and rescue operations or perform environmental monitoring and remediation.
FiloBot has a head equipped with light and gravity sensors. At its base, a tiny 3D printer lets out a filament of thermoplastic material. The filament assumes a circular shape with a diameter of 4 cm and builds the stem-like body of the robot, which is anchored to a station with power supplier, filament spooler, and fans. The robot can be made to bend by modulating the speed at which the filament is plotted around the circumference, deposing more material on one side than on the other. Depending on the behaviour required, FiloBot can autonomously choose a bending angle based on gravity and light and then adjust its parameters to achieve that angle.
Ecologists have hypothesized that, when looking for a support, climbing plants are attracted by shade, a behaviour known as skototropism, as opposed to phototropism when the plant grows towards light. By matching the temperature, plotting and speed of the filament’s extrusion to the wavelengths, the authors made FiloBot search for the support of a plant, growing over one of its leaves in the shadow of the overhanging one and thus towards the trunk. The twining to a plant trunk was achieved by continuously measuring the angle between the robot’s growing direction and gravity, and adjusting the growth parameters accordingly.
Climbing plants are also able to regulate the strength of the stem depending on their configuration. In the young stages of growth or when crossing voids, they grow thicker to go against gravity and carry their own weight. When they are twined to a support, they can be lighter and more flexible. Similarly, the authors achieved a lighter structure by increasing the feeding speed or decreasing the extrusion temperature. “This allows the saving of energy and also growth acceleration, prolonging the system's lifespan and extending its capabilities,” explains Emanuela Del Dottore, a researcher at IIT and first author of the paper.
FiloBot is not yet able to autonomously switch between different behaviours by weighing the impacts of gravity and light on its growth. “Complete autonomy is the next challenge we want to address,” Del Dottore says.Mazzolai adds that artificial plants that can intertwine could pave the way for new applications, such as self-growing infrastructures.“Mazzolai group's work in growing robot structures by additive manufacturing is unique and inspirational to the rest of us,” says Ian Walker, roboticist at the University of Clemson in the United States, whose group also works on bioinspired growing robots. “This work is an important step towards applications in outdoor environments, which is the overall goal of the field.”
