Reconfigurable constriction-based soft actuation for decorative morphing flowers

Most soft actuators producing joint-like deformations rely on the expansion of materials or on the use of multiple chambers in equilibrium while requiring additional structures for inter-connecting the joints. This paper introduces a new soft pneumatic actuator where a constriction placed on an inflatable tube allows the tube to bend around the constriction through the formation of a crease around the constriction. The bending of the tube then changes as the shape of the crease change under a change in pressure without relying on the expansion of the material. This results in an actuator that has a single chamber where multiple constrictions can be placed and freely re-arranged to form different structures as their insertion is nonpermanent. The constriction is also able to induce lateral bending deformations such that the actuator can assume a helical configuration using multiple constrictions spaced over the length of the actuator. The performance of different constriction designs in terms of bending angle without any payloads and with additional payloads is presented followed by their implementation in three different designs of morphing decorative flowers. The actuator itself does not produce a large force and its range of motion is quite limited, but it has a unique set of properties that make it ideal for visual and creative applications as well as educational purposes.