Engineers are always looking for innovative ways to overcome the challenges in creating robots, especially when it comes to soft robots. Recently, a group of researchers from Princeton and North Carolina State Universities combined the ancient art of paper folding with modern materials science to develop a caterpillar robot that is soft, highly flexible and steerable.
“The new design overcomes these problems by building the steering system directly into the robot’s body,” said Tuo Zhao, a postdoctoral researcher at Princeton.
Soft robots have been a challenging field of study due to their difficulty in being steered without compromising their flexibility. Often, conventional steering systems end up making the robot rigid. However, the engineers behind this new project have found an innovative solution by integrating the steering system directly into the robot’s body. This was achieved by constructing the robot from modular cylindrical segments, which can operate independently or come together to form a longer unit.
In their article entitled “Modular Multi-degree-of-freedom Soft Origami Robots with Reprogrammable Electrothermal Actuation”, published in the journal Proceedings of the National Academy of Sciences, the researchers describe in detail how they built and implemented this innovative concept.
“Each segment can be an individual unit, and they can communicate with each other and come together on command,” said Zhao. “They can separate easily, and we use magnets to connect them.”
The secret behind the robot’s ability to move and steer lies in the flexibility and adaptability of the cylindrical segments. Each segment can operate individually or in conjunction with others, allowing the robot to crawl back and forth, handle loads and assemble itself into longer formations. In addition, the modularity of the system allows the robot to function both as a single unit and as part of a swarm, providing additional flexibility in its application.
“The concept of modular soft robots can provide insights into future soft robots that can grow, repair and develop new functions,” the authors write in their article.
The development of this robot would not have been possible without collaboration between different disciplines and institutions. The work involved a multidisciplinary team, with researchers from the fields of civil engineering, materials and mechanics, among others. North Carolina State University played a crucial role in developing the mechanism for controlling the robot’s bending and flexing movements. This mechanism was created using materials that shrink or expand differently when heated, combined with a stretchable heater made of a network of silver nanowires.
“Silver nanowire is an excellent material for making stretchable conductors. Stretchable conductors are building blocks for a variety of stretchable electronic devices, including stretchable heaters,” said Yong Zhu, Andrew A. Adams Distinguished Professor in the Department of Mechanical and Aerospace Engineering at N.C. State and one of the lead researchers.
Shuang Wu, a post-doctoral researcher in Zhu’s lab, pointed out that previous projects carried out in the lab have used the extensible heater to induce continuous bending of a two-layer structure. “In this work, we achieved localized, sharp folding to trigger the origami pattern. This effective actuation method can be generally applied to origami structures (with folds) for soft robotics,” said Wu.
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The scientists noted that the robot in its current form has a limited speed and are dedicated to improving its locomotion in future iterations. In addition, Zhao mentioned that the team is planning to carry out exploratory experiments involving various shapes, patterns and levels of stability, with the aim of optimizing both the speed and the precision of the robot’s direction.
