Paper-Based Robotics With Stackable Pneumatic Actuators

Paper continues to receive attention as a material for electronics and robotics due to its low-cost, recyclability, and foldability. In recent years, there has been an increasing amount of literature on origami/kirigami robots made of paper-like materials, which are thin, foldable, and intrinsically unstretchable. Although the word “origami/kirigami” means folding/cutting paper, these robots can be made of both cellulose-based materials and plastic sheets. Although paper-like materials are unstretchable, these origami/kirigami robots, like soft robot made of elastomers, are able to adapt to their surroundings or mimic the movement of living organisms, such as a worm and an octopus, by employing highly deformable structures.

This work presents a unique approach to the design, fabrication, and characterization of paper-based robotic systems consisting of stackable pneumatic actuators. These paper-based actuators (PBAs) use cellulose-based paper, accordion-like structures, and direct coupling with pressure for extension and bending. The study contributes to our scientific and engineering understanding of foldable components under applied pressure through the construction of stretchable and flexible structures with intrinsically unstretchable materials. Experiments showed that a paper-based actuator possesses a power-to-weight ratio (PWR) greater than 80 W/kg, which is more than four times that of human muscle.

This work illustrates the stackability and functionality of paper-based actuators with two simple robotic systems: a parallel manipulator and a legged locomotor. The manipulator consists of an array of PBAs which can bend to a specific direction while inflating the corresponding actuator. In addition, the stacked actuators in the manipulator can rotate in opposite directions to compensate for relative rotation at the ends to work in parallel and manipulate the platform. The locomotor utilizes the rotation of PBAs to apply or release the friction between the feet and the ground. Furthermore, we used numerical and analytical methods to study the influence of folding patterns on PBAs. A numerical model of inflatable actuators included in this work predicts the qualitative mechanical performance of these actuators as a function of dimensional specifications and folding patterns. An analytical model calculates the coordinate of each vertex of a PBA for characterizing the elongation and rotation of PBAs with different folding patterns during the process of unfolding.

Overall, the novelty of this work is using stacked origami actuators to realize the function of conventional robotic systems, rather than simple elongation or rotation. Future origami robots made of paper-like materials may be suitable for single use in contaminated or unstructured environments or for low-cost educational materials.