In the future, soft robots will be able to take on tasks that conventional robots fail at. For example, they could be used in terrain that is difficult to access and in environments where they are exposed to chemicals or radiation that would harm electronically controlled metal robots. However, this requires these soft robots to be controllable without any electronics.

A research team at the University of Freiburg led by Dr. Stefan Conrad, Dr. Falk Tauber, Joscha Teichmann and Prof. Dr. Thomas Speck from the Cluster of Excellence "Living, Adaptive and Energy-autonomous Materials Systems (livMatS)" has taken on this challenge. The team has now developed 3D-printed pneumatic logic modules that control the movements of soft robots using air pressure alone. These modules enable logical switching of the air flow and can thus imitate electrical control. The modules make it possible for the first time to produce flexible and electronics-free soft robots entirely in a 3D printer using filament made from conventional printing material. Dr. Stefan Conrad: "Our design enables anyone with experience in 3D printing to produce such logic modules and use them to control a soft robot without the need for high-end printing equipment. This marks a significant step towards completely electronics-free pneumatic control circuits that can replace increasingly complex electrical components in soft robots in the future."

The structure of the modules

The modules consist of two pressurized chambers. A 3D-printed channel runs between the chambers. By pressing on the channel, the chambers can stop the air flow in it and regulate it like a valve. By opening and closing the valve in a targeted manner, the modules can perform the Boolean logical functions "AND", "OR" and "NOT" in a similar way to electrical circuits and direct the air flow into the movement elements of the soft robot. Which function the individual module performs is determined by the chambers into which air pressure is applied. Depending on the material selected, the modules can be operated with a pressure of between 80 and more than 750 kPa. Compared to other pneumatic systems, they have a fast response time of around 100 ms.

"The application possibilities of these modules are enormous. We have developed a flexible 3D-printed robotic slider that is controlled by air pressure using an integrated circuit. The flexibility of the logic modules is demonstrated by the fact that this slider can even withstand the load of a car driving over it," explains Dr. Falk Tauber. "As an example of more complex control systems, we have also developed an electronics-free drinks dispenser."

The research team's results were published in the renowned journal "Science Robotics".