Discussion

[Discuss here your results in light of current knowledge.]

Conclusion

Our work first aim to present an innovative design using bistable metal strip and shape memory alloy Nitinol to fabricate a biomimetic actuator as a swimming device, which exhibited both slow moving and fast snapping capability like an octopus. We hope to inspire more research on combining different materials to achieve novel designs for more applications. Sensing application is just one of the many applications this device can achieve. Remote sampling collecting, video recording, humidity, temperature and air quality monitoring can all be potentially realized with thoughtful integration. However, we do need to consider the long time memory loss of Nitinol wire after more repetitions, which was not exhaustedly investigated in this work. Future research should look into this and come up with an estimate time for Nitinol wire memory exhaustion. Also, how to recharge the battery when the device is far away in the field, and how to make sure we don’t lose connection when battery runs out, etc. More importantly, bio-fouling can be a big challenge for devices that are deployed and immersed in water environment for long period of time. Special protective coatings or antifouling design for the device should be investigated.
In summary, a wirelessly controlled, programmable, swimming device was developed. The properties of the Nitinol alloy, bistable metal strips were investigated to find out optimum design. Hydrogel coating was chosen to provide a stable under-water environment for the Nitinol wires, which facilitates under-water actuation. A fish fin like PDMS flipper was also designed and increased the swimming ability. The swimming device could navigate in all directions and could be controlled wirelessly and easily programmable thanks to the untethered design with a portable battery and wireless control module. We also showcased its successful integration with an etalon-based sensing platform, which can potentially inspire more innovative future applications.