Soft robotics is an emerging field where robots are made of soft, pliable materials as opposed to rigid ones. Soft growing robots can create new material and “grow” as they move. These machines could be used for operations in remote areas where humans can’t go, such as inspecting or installing tubes underground or navigating inside the human body for biomedical applications. Current soft growing robots drag a trail of solid material behind them and can use heat and/or pressure to transform that material into a more permanent structure, much like how a 3D printer is fed solid filament to produce its shaped product. However, the trail of solid material gets more difficult to pull around bends and turns, making it hard for the robots to navigate terrain with obstacles or winding paths. Scientists have now developed a first-of-its-kind, plant-inspired extrusion process that enables synthetic material growth. The new approach will allow researchers to build better soft robots that can navigate hard-to-reach places, complicated terrain and potentially areas within the human body.

An interdisciplinary team of scientists and engineers at the University of Minnesota (Minneapolis, MN, USA) developed the new means of extrusion, a process where material is pushed through an opening to create a specific shape. Using this new process allows the robot to create its synthetic material from a liquid instead of a solid. The researchers were inspired by how plants and fungi grow. Plants use water to transport the building blocks that get transformed into solid roots as the plant grows outward.

The researchers were able to mimic this process with synthetic material using a technique called photopolymerization, which uses light to transform liquid monomers into a solid material. Using this technology, the soft robot can more easily navigate obstacles and winding paths without having to drag any solid material behind it. This new process also has applications in manufacturing. Since the researchers’ technique only uses liquid and light, operations that use heat, pressure and expensive machinery to create and shape materials might not be needed.

“We were really inspired by how plants and fungi grow,” said Matthew Hausladen, first author of the paper and a Ph.D. candidate in the College of Science and Engineering. “We took the idea that plants and fungi add material at the end of their bodies, either at their root tips or at their new shoots, and we translated that to an engineering system.” 

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