Abstract
Bioinspired swimming robots with various applications have elicited substantial interest owing to their outstanding performance. On the macroscale, national marine plays a significant role in a country’s economic development and global military status. Exploration of underwater resources mainly relies on traditional screw-propeller propulsion because of its mature technology, which, however, also suffers from critical deficiencies, such as low efficiency and maneuverability, large size and weight, and high costs. On the microscale, untethered microrobots have exhibited notable potential in various biomedical applications, such as minimally invasive diagnosis, drug and cell delivery, and tissue engineering. Although a few microrobots have been developed for this purpose, innovative and reliable microrobots remain to be explored. In over millions of years of evolution and natural selection, swimming aquatic organisms have generated distinguished body mechanism and remarkable swimming capacity for sophisticated and challenging living environment. Mimicking their propulsive mechanisms and configurations offers important possibilities and motivations to robot design and control methods. In this study, two types of bioinspired swimming robots on the macro- and microscale are investigated and proposed. This thesis is divided into two parts.In the first part, a bioinspired robotic fish with an integrated oscillation and jet propulsive mechanism is presented. This robotic fish employs two caudal fins that are equipped in parallel at the fish tail, and the shape of the caudal fin is designed to follow the shape of flounder to promote the acceleration ability. The two caudal fins flap oppositely and generate opposing lateral forces, which counteract the yaw motion and lead to a stable and high-speed swimming locomotion. The influence of the distance between the two caudal fins on the swimming performance is numerically and experimentally investigated. Results demonstrate that a critical distance exists at which the robotic fish can exhibit both oscillatory and jet propulsion capabilities; in this circumstance, the robotic fish can reach the maximum swimming speed. This robotic fish can attain many maneuverability capabilities, such as turning, braking, rising, and sinking in conjunction with pectoral fins. The dual caudal-fin propulsive mechanism, which combines oscillatory and jet propulsion, greatly enhances the maneuverability and stability of the robotic fish.
In the second part, a bioinspired magnetically driven microswimmer that mimics the undulatory propulsive mechanism is proposed. This microswimmer consists of multiple rigid segments connected by joints and is fabricated integrally by 3D laser lithography without further assembly, thereby simplifying microrobot fabrication while enhancing structural integrity. A layer of nickel (Ni) is deposited on the first segment (head) of the microswimmer to enable magnetic actuation. The head segment oscillates under an oscillating uniform magnetic field, and its oscillation is transferred to its posterior segments. Accordingly, undulatory propulsion is generated. This work is the first to demonstrate that microswimmers constructed with multiple rigid components can also achieve undulatory locomotion and swim forward along guided directions in the low Reynolds number regime.
In summary, this study shows that the mimicry of biological locomotion strategies can increase the diversity, agility, and efficiency of designed swimming robots on the macro- and microscale. The two innovative swimming robots invented in this work provide new approaches to robot design, which can potentially benefit underwater explorations and biomedical applications.
| Date of Award | 11 Jun 2019 |
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| Original language | English |
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| Supervisor | Dong SUN (Supervisor) & Shiwu Zhang (External Supervisor) |