Self-growing robots are an emerging solution in soft robotics as they show potential in navigating, exploring, and colonizing their surroundings. However, they are limited in their ability to grow and move in unstructured 3D spaces. In a recent study, a team of researchers addressed this challenge by taking inspiration from climbing plants.
Adaptive Behaviors of Climbing Plants
Compared with other types of plants, climbing plants have the ability to adapt their growth to a wide range of environmental contexts, from grasslands to riverbanks and forests. Their unique adaptations allow them to compete for sunlight, for which they invest minimal resources for vertical growth.
Ecologists believe that climbing plants are attracted by shade when looking for support. This behavior is known as skototropism, an ability opposed to phototropism where the plant grows towards light.
Climbing plants can also regulate the strength of their stem based on their configuration. During their young stages of development or when crossing voids, they can grow thicker to resist gravity and carry their own weight. Meanwhile, they can make themselves lighter and more flexible by twinning to a support.
Plant-Inspired Machine
At the Italian Institute of Technology (IIT), experts have developed a growing robot which can respond to light and gravity by adopting some of the adaptive behaviors of climbing plants. Their study is discussed in the paper "A growing soft robot with climbing plant-inspired adaptive behaviors for navigation in unstructured environments."
The innovative machine, named FiloBot, is the culmination of a 10-year study led by researcher Barbara Mazzolai. The robot was made to mimic the growth of climbing plants by adapting the behavior of plant roots and by using 3D printing.
In challenging and crowded environments such as tropical rainforests, climbing plants grow against gravity and utilize supports to win the competition for light. They support themselves by using tendrils, hooks, or twines, a strategy which inspired the creation of FiloBot.
FiloBot's head is equipped with sensors that can detect light and gravity. At its base, there is a small 3D printer which lets out a filament of thermoplastic material. This filament assumes a circular shape to build the stem-like body of the robot. Meanwhile, the machine itself is anchored to a station with fans, filament spooler, and power supplier.
In terms of weight, scientists achieved a lighter structure by increasing the feeding speed or by decreasing the extrusion temperature. This allowed them to save energy and accelerate growth, prolonging the robot's lifespan and further extending its capabilities.
The autonomous robot demonstrates the ability to navigate unstructured environments and cross voids. These skills are harder to emulate for robots with legs or wheels. Such features will be beneficial in supporting search and rescue operations and performing environmental monitoring and remediation.
FiloBot is still not yet able to switch autonomously between different behaviors by weighing the impacts of light and gravity on its growth. According to IIT researcher Emanuela Del Dottore, complete autonomy is the next challenge that they aim to address. They plan to develop self-growing infrastructure by taking inspiration from artificial plants that can intertwine.
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