"Robot is Flexible" Starfish Robot Applying Architectural Technology Emerges

UNIST Professor Kim Ji-yoon's Team Develops Tensegrity Structure 'Soft Robot'

A starfish robot that moves flexibly.

[Asia Economy Yeongnam Reporting Headquarters Reporter Kim Yong-woo] Unlike rigid and rough-moving robots, a robot application technology that moves flexibly like a ‘bulgasari’ has been developed, attracting attention. This technology creates robots by applying structures used in lightweight and sturdy buildings.

UNIST (President Lee Yong-hoon) announced on the 27th that Professor Kim Ji-yoon’s team from the Department of Materials Science and Engineering developed a technology to produce ‘soft robots’ that are both flexible and robust.

They devised an easy way to implement the complex tensegrity structure used in buildings and succeeded in producing a movable ‘bulgasari’ robot.

The tensegrity structure is a framework where ‘strong materials’ capable of bearing weight and ‘flexible materials’ that are taut like threads are interwoven like warp and weft.

This structure is mainly used in buildings because it offers the advantage of achieving high strength and flexibility with minimal materials.

When people think of robots, they often imagine steel robots like Mazinger Z or metal-arm robots used in industrial sites, but recently, new types of robots such as caregiving robots or pet robots have emerged.

These robots that interact with humans need to have soft and flexible characteristics. Relying solely on the soft properties of materials when making ‘soft robots’ makes it difficult to implement complex robot drive systems.

Professor Kim Ji-yoon (left), who developed the flexible robot, and researcher Lee Ha-jun (center), the first author, along with the UNIST research team.

Professor Kim Ji-yoon’s research team developed a manufacturing method that applies the robust yet flexible tensegrity structure to various soft robot designs.

Because the tensegrity structure consists of materials with different properties connected in midair, it is difficult to produce such robots using conventional 3D printing techniques.

The team devised a method to realize complex tensegrity structures by combining 3D printing with water-soluble sacrificial molds.

They first 3D print compression materials that can withstand heavy loads and sacrificial molds, then insert flexible tensile materials inside the sacrificial molds. Since the sacrificial molds dissolve in water, they can be easily removed.

Researcher Lee Ha-jun, the first author, explained, “By combining the representative bottom-up manufacturing method of 3D printing with the top-down method of ‘etching,’ we were able to easily realize complex tensegrity structures.”

Using the developed structural manufacturing method and design techniques, the research team produced tensegrity structures in various shapes such as cubes, toroids, and triangular prisms.

They also assembled an electrically driven bulgasari robot with five legs using the fabricated tensegrity structures as basic modules.

Because the tensegrity structure was applied, the robot can walk and change its moving direction. Furthermore, by applying smart materials that ‘move autonomously’ in response to external stimuli, bulgasari robots can be created. In fact, they produced a bulgasari robot that contracts and expands autonomously by applying smart magnetic materials.

Professor Kim Ji-yoon said, “By utilizing the characteristics of the tensegrity structure, it is possible to create various meta-structures with unique mechanical properties that are difficult to achieve with ‘materials’ alone and do not exist in nature.”

He added, “This research is significant because it developed a technique to easily and quickly realize complex tensegrity structures in desired shapes. It will greatly aid the development of soft robots by enabling the easy production of flexible and robust blocks with various shapes and functions.”

This research was published online on August 26 in the prestigious robotics journal ‘Science Robotics.’ The research was supported by the National Research Foundation of Korea (NRF) and the Korea Evaluation Institute of Industrial Technology.

This content was produced with the assistance of AI translation services.