Building Better Soft Robots Is a Snap

Everything from medicine to manufacturing, search and rescue operations, and space exploration could benefit from advances in soft robotics. These unique robots are adaptable, flexible, and have the ability to safely interact with delicate or fragile objects in a way that traditional systems cannot. However, compared to their rigid counterparts, today’s soft robots are far less advanced.

One of the primary reasons they are lagging so far behind is the challenge of building soft actuators. Precision control is very difficult to achieve when the actuator can bend, twist, stretch, and generally flop about freely in any direction. This is especially true when an actuator is designed to perform a wide range of movements. Not only are such devices challenging to develop, but they also tend to have extremely complicated control systems, with tubes running every which way. Robots that utilize these types of actuators are unlikely to ever see the light of day outside of a research lab.

Researchers at Seoul National University have just described a novel type of soft actuator that could be much more practical for real-world use. Robots built using this technology rely on just a single air input to execute complex motions. Unlike existing soft robots, which require multiple air sources or complex electronic control systems, this innovation enables smooth, continuous motion and sudden shape transformations with a single actuation source.

The actuators were built using what the researchers call a Snap Inflatable Modular Metastructure (SIMM), an advanced mechanism that uses a snap-through effect similar to how a Venus flytrap suddenly closes or how a toy jumping popper flips inside out. By incorporating bistable shells — structures that can quickly switch between two stable states — the robot can morph its shape in complex ways in response to air pressure changes. The robot can then return to its original shape by deflating, completing a reversible morphing cycle.

To demonstrate the capabilities of their system, the team built two soft robot prototypes. One leverages the SIMM to crawl along the ground, much like an earthworm, using blasts of compressed air. It also has the unique ability to grip and climb cables, which could come in quite useful in search and rescue operations, in particular. The other robot moves forward by bending its body, somewhat like the crawling robot. But this one can also rapidly transform and expand its body shape, allowing it to pick up objects, change its direction of travel, or traverse complex terrain.

While challenges remain, such as improving durability and optimizing material selection, this new approach to soft actuation represents a significant step forward in soft robot control systems. By reducing the number of required components, the researchers have also decreased the cost, weight, size, and power consumption of these robots. With further research and development, these robots could soon transition from laboratory experiments to real-world applications, transforming fields ranging from healthcare to industrial automation.