Researchers develop soft robot that easily transitions from land to sea

Inspired by nature, these soft robots received their amphibious upgrade with the help of bistable actuators.
Kavita Verma
Carnegie Mellon University’s researchers develop a robot that easily shifts from sea to land.

Carnegie Mellon University  

Researchers at Carnegie Mellon University have created a soft robot that can effortlessly transition from walking to swimming or from crawling to rolling.  

"We were inspired by nature to develop a robot that can perform different tasks and adapt to its environment without adding actuators or complexity," said Dinesh K. Patel, a postdoctoral fellow in the Morphing Matter Lab in the School of Computer Science's Human-Computer Interaction Institute. "Our bistable actuator is simple, stable and durable, and lays the foundation for future work on dynamic, reconfigurable soft robotics."

The role of electric currents

The bistable actuator is constructed from 3D-printed soft rubber, which contains shape memory alloy springs that contract on contacting electrical currents, causing a bend in the actuator. The team used this bistable motion to change the robot’s shape. Once the changes in the robot's shape occur, it remains stable until another electrical charge changes it back to its earlier configuration. 

"Matching how animals transition from walking to swimming to crawling to jumping is a grand challenge for bio-inspired and soft robotics," said Carmel Majidi, a professor in the Mechanical Engineering Department in CMU's College of Engineering.

For instance, the team created a robot with four curved actuators fitted in the corners of a body equal to the size of a cell phone made of two bistable actuators. On land, these bent actuators act as legs, allowing the robot to walk. In the water, the bistable actuators change the robot’s shape, which puts the curve actuators in a perfect position to behave like propellers helping it swim.

"You need to have legs to walk on land, and you need to have a propeller to swim in the water. Building a robot with separate systems designed for each environment adds complexity and weight," said Xiaonan Huang, an assistant professor of robotics at the University of Michigan and Majidi's former Ph.D. student. "We use the same system for both environments to create an efficient robot."

The team created two more robots: One with the ability to jump and crawl and one inspired by pill bugs and caterpillars that can roll and crawl. 

The future of the soft robots

In the future, it is assumed that these soft robots will be used for rescue missions or to interact with coral and sea animals. With the help of heat-activated springs, the actuators could be utilized for haptics, environmental monitoring, and reconfigurable electronics and communication.

"There are many interesting and exciting scenarios where energy-efficient and versatile robots like this could be useful," said Lining Yao, the Cooper-Siegel Assistant Professor in the HCII and head of the Morphing Matter Lab.

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