Autonomous Robot Grows Stem by Responding to Light and Gravity

Researchers in Italy have developed a remarkable robot that mimics the growth patterns of a plant. Known as FiloBot, this innovative creation is the result of the Bioinspired Soft Robotics Laboratory at the Fondazione Istituto Italiano di Tecnologia in Genova.

FiloBot has the ability to build its own stem-like body, which can reach several meters in length. It permanently curves in response to light, dark, or gravity, and can adjust the strength of its body based on its environment.

The robot consists of three main parts: a 40mm diameter head, a body of the same diameter, and a base unit. Initially, the head sits on the base unit without a body.

Growth begins when the head starts to rotate, depositing a thin stream of melted plastic from a point on its edge. This plastic hardens into a circle, and ring after ring is deposited in the form of a continuous spiral. Gradually, the body is formed, lifting the head layer by layer.

The head of FiloBot is a marvel of miniaturization, containing various components such as motors, a rotation mechanism, a deposition mechanism, a Bluetooth microcontroller, a three-axis accelerometer, and a color sensor. The robot operates autonomously, with its growth being emergent without pre-planning or external guidance.

The body of FiloBot was grown in the lab and was later placed around a tree for fun. Steering is achieved by depositing more or less plastic at different points during the 360° rotation. The same technique is used to make the body stronger or more resource-frugal depending on the situation. The robot can adjust its growth rate between 2 and 7mm per minute.

The motivation for steering is similar to that of a plant, relying on gravity perception and the levels of blue, red, and far-red. The researchers have developed algorithms by comparing the resulting growth with real plants, demonstrating behaviors such as twining, gravitropism, phototropism, and skototropism.

To rotate the head, FiloBot utilizes a short sleeve inside the body with springs that push outward. The springs are designed to resist slipping circularly inside the hollow body while easily sliding longitudinally as the body extends. The rotation is achieved through teeth cut into the inside of the sleeve that mesh with a gear on the end of a motor.

The second motor in FiloBot hauls 3D printing filament up the length of the body from a spool in the base unit. It pushes the filament out through a deposition nozzle via a heater that melts it. All the necessary electronics are compactly packed into a space of approximately 42cm3 and weighing 82.5g.

To prevent the plastic feed filament from tangling, the storage reel inside the base unit sits on a freely-rotating joint. Two wires pass up the inside of the body to supply power to the head via slip-rings built into the head. Cooling air for the head is provided by fans in the base unit.

The development of FiloBot was a collaborative effort between the Fondazione Istituto Italiano di Tecnologia and the University of Montpellier in France. The research and findings have been published in a paper titled "A growing soft robot with climbing plant–inspired adaptive behaviors for navigation in unstructured environments" in Science Robotics.