Synthetic material allows soft robots to grow like plants

A team of scientists and engineers from the University of Minnesota has developed a plant-inspired extrusion process that enables the growth of synthetic materials, which could allow soft robots to grow like plants. The method is innovative and novel, and the resulting robots could navigate narrow places, complicated terrain and even areas of the human body.

The research, which was funded by the National Science Foundation, was published in the Proceedings of the National Academy of Sciences (PNAS).

Robots that “grow” as they move

Chris Ellison is a lead author on the paper and a professor in the Department of Chemical Engineering and Materials Science at the University of Minnesota.

“This is the first time these concepts have been fundamentally demonstrated,” Ellison said. “The development of new manufacturing methods is essential for the competitiveness of our country and to bring new products to people. On the robotics side, robots are increasingly being used in dangerous and remote environments, and these are the types of areas where this work could have an impact.

Soft robots are robots made of soft, bendable materials instead of rigid materials, and these new types of soft-growing robots can generate new materials and “grow” as they move. They could be applied to a variety of applications, and they are particularly useful for navigating in remote areas that humans cannot access. Actual applications could include inspections or installation of underground tubes, or navigation inside the human body.

The soft-growing robots we currently have access to leave a trail of solid material behind, and they use heat and/or pressure to transform the material into a more permanent structure. The researchers compare this to a 3D printer, which is fed solid filament to produce a shaped product. Despite this, the soft material becomes difficult when the robot has to move around bends, which means that it is difficult for the robots to pass certain obstacles.

Develop new means of extrusion

To solve this problem, the team developed a new means of extrusion. The new process involves material being pushed through an opening to create a specific shape, and it allows the robot to create its synthetic material from liquids instead of solids.

Matthew Hausladen is the first author of the article and a Ph.D. student in the Department of Chemical Engineering and Materials Science at the University of Minnesota Twin Cities.

“We were really inspired by how plants and fungi grow,” Hausladen said. “We took the idea that plants and fungi add material to the end of their bodies, either at the end of their roots or at their new shoots, and we translated that into a system of engineering.”

The researchers wanted to mimic the process of plants using water to transport the building blocks that turn into strong roots as the plant grows outward. To achieve this with a synthetic material, the team relied on a technique called photopolymerization, which uses light to turn liquid monomers into a solid material. The soft robot can use this technology to more easily navigate obstacles and bends without the need to drag solid materials.

Potential real-world applications

The team says the new process could also be applied in manufacturing, especially applications that use heat, pressure and machines to create and shape materials that might not be needed.

“A very important part of this project is that we all have materials scientists, chemical engineers, and robotic engineers involved,” Ellison continued. “By bringing all of our different expertise together, we really brought something unique to this project, and I’m sure none of us could have done it alone. It’s a great example of how collaboration allows scientists to solve very difficult fundamental problems while having a technological impact. »

The team of researchers also includes researchers from the Department of Chemical Engineering and Materials Science at the University of Minnesota, Boran Zhao (postdoctoral researcher) and Lorraine Francis (professor emeritus of the College of Science and Engineering); and University of Minnesota Department of Mechanical Engineering researchers Tim Kowalewski (associate professor) and Matthew Kubala (graduate student).