Conclusion
In this paper, we have presented a soft fluidic bending actuator that undergoes characteristic quasi-sequential deployment and bending motion, attributed by an asymmetric extension of dual-origami components; a folded fluidic chamber and a folded strain-limiting layer. The proposed design embodies spatial benefits of deployment and retraction that originate from origami architectures, as well as inherent adaptiveness of soft fluidic robots. The dual-origami soft fluidic bending actuators can be directly and automatically fabricated through accessible 3D printing technology, and additional heat treatment post-processing was introduced to reinforce the material adhesion. Furthermore, we have investigated the kinematic features of the flexible soft origami robot and established a bending-to-deployment ratio factor to quantify the dominance shifting from deployment to bending. The relationship between design parameters and the motion was also explored and the tradeoff relationship between deployment and bending was demonstrated through pre-programming of six-module dual-origami fluidic bending actuators. Moreover, we built the deployable two-finger gripping unit that can generate high holding force (~3.15 kg, weight 56.8 g), and applied them into a versatile soft gripper that cooperate with a commercial suction gripper. The demonstration has successfully shown that the deployable finger units can not only grow and adapt to various objects, but also can make place to the suction cup for efficient use of the entire system.
We believe that our approach provides a new design guidance of soft fluidic robots to embody the grow-and-retract motion with a small initial form factor that considers space usage, differentiating from conventional design methods that primarily focus on motion generation. In addition, the proposed design principle is implemented by non-stretchable and flexible materials, allowing wide range of material choice compared to our previous work using stretchable materials.\cite{Katzschmann2018,Heng_2021,Cianchetti_2014} Future work may include fabrication using light and thin materials such as thermoplastic sheets (e.g., polypropylene, polyethylene), composite fabrics, and papers, to improve scalability and functionality. Further improvement such as sensor integration, real-time control and analytical modeling would complement the complexity of the combined motion of deployment and bending. We expect that the unique property of a small form factor soft robot with grow-and-retract motion would be considered as a powerful option for applications in next-generation soft robotic systems, including portable or mobile application, medical devices, wearable robots, and integrated robotic systems.
Acknowledgements
This work was supported by the National Research Foundation of Korea (NRF) (NRF-2016R1A5A1938472) and the Technology Program (20008908) funded by the Ministry of Trade, Industry & Energy (MOTIE, Korea).
Conflict of interest
The authors declare no conflict of interest.