These Real-World Transformers Use a 3D-Printed Soft Actuator to Flip Locomotive Modes
Flipping between two states with the application of power, this soft rubber actuator offers real flexibility.
Researchers from Carnegie Mellon University and the University of California have designed a novel actuator that can be used to built more flexible soft robots — including machines capable of transforming between walking on land land swimming across the sea.
"We were inspired by nature to develop a robot that can perform different tasks and adapt to its environment without adding actuators or complexity," explains first author Dinesh K. Patel, a post-doctoral fellow in Carnegie Mellon's Morphing Matter Lab. "Our bistable actuator is simple, stable and durable, and lays the foundation for future work on dynamic, reconfigurable soft robotics."
The actuator itself is relatively simple, produced from rubber on a 3D-printer — but is fitted with shape-memory alloy springs. When an brief electrical current is applied, the springs cause the actuator to snap into its second configuration — where it remains until a second current is applied to snap it back again, hence "bistable."
To prove the actuator's flexibility, the team built a series of robot prototypes. The first is a true transformer, capable of using the curved actuators as propellers in the water then flipping them into functional legs for locomotion across the land. A second prototype can switch between crawling and jumping, while a caterpillar-inspired third can crawl or roll.
"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," says Xiaonan Huang, assistant professor of robotics and co-author of the paper, of the prototype. "We use the same system for both environments to create an efficient robot."
Being primarily made from a dense rubber helps with durability, too: the prototype actuators were tested to hundreds of state-changes with no loss of performance, and even subjected to a torture test by having a researcher repeatedly run over them with a bicycle to no ill effect. The team has also suggested the possibility to replace the electrically-actuated springs with heat-actuated versions for broader applications including environmental monitoring and haptic interfaces.
The researchers' work has been published under open-access terms in the journal Advanced Materials Technologies.