Researchers at Brown University have taken the first steps towards creating a network of interconnected, autonomous robots that mimic the swimming behavior of krill to navigate the ocean’s dark depths. In a study published in Scientific Reports, the team introduces Pleobot, a small robotic platform designed to emulate the metachronal swimming method employed by krill.
This innovative platform not only aids in understanding the intricate swimming technique of these remarkable aquatic creatures but also serves as a foundation for the development of agile and maneuverable underwater robots. Pleobot, currently comprised of three articulated sections, replicates the precise movements of krill during metachronal swimming.
By drawing inspiration from the extraordinary swimming abilities of krill, which encompass acceleration, braking, and turning, the researchers showcase Pleobot’s capabilities in emulating the leg motions of swimming krill. The study offers fresh insights into the fluid-structure interactions necessary for sustaining stable forward swimming in these fascinating organisms.
Pleobot’s capabilities emulate the leg motions of swimming krill. (Image: “File: Antarctic krill (Euphausia superba).jpg” by Krill666.jpg: )
The potential impact of Pleobot extends beyond the realm of scientific curiosity — it holds the promise of leveraging over 100 million years of evolutionary perfection to engineer more efficient and effective robots for ocean navigation. “Experiments involving organisms are inherently challenging and unpredictable,” explains Sara Oliveira Santos, the lead author of the study and a Ph.D. candidate at Brown’s School of Engineering.
“Pleobot provides us with an unprecedented level of resolution and control, enabling comprehensive investigations into the aspects of krill-like swimming that contribute to their exceptional maneuverability underwater. We aimed to design a comprehensive tool for understanding krill-like swimming, encompassing all the intricate details that make krill such agile swimmers.”
This collaborative effort between researchers at Brown University and the Universidad Nacional Autónoma de México seeks to unravel the mysteries of metachronal swimming, enabling a deeper understanding of how krill thrive in complex marine environments and accomplish massive vertical migrations.
By precisely replicating the leg movements and shape-changing appendages of krill, Pleobot allows for precise measurements and comparisons that are otherwise impossible to obtain using live animals.
Image: Scientific Reports (2023). DOI: 10.1038/s41598-023-36185-2
The metachronal swimming technique
Characterized by the sequential deployment of swimming legs in a wave-like motion from back to front, the metachronal swimming technique imparts remarkable maneuverability to krill. The researchers envision future deployable swarm systems capable of mapping Earth’s oceans, undertaking large-scale search-and-recovery missions, or exploring the oceans of celestial bodies such as Europa, one of Jupiter’s moons.
“This study marks the initial phase of our long-term research goal to develop the next generation of autonomous underwater sensing vehicles,” states Monica Martinez Wilhelmus, Assistant Professor of Engineering at Brown University. “Understanding fluid-structure interactions at the appendage level empowers us to make informed decisions about future designs.”
The researchers have achieved active control over two leg segments of Pleobot, while the biramous fins feature passive control — making it the first platform to replicate the intricate opening and closing motion of these fins.
Pleobot primarily consists of 3D printable parts
Constructed at ten times the size of real krill, Pleobot primarily consists of 3D printable parts, with its design made freely available to other teams for further exploration of metachronal swimming, not only in krill but also in organisms like lobsters. The study unveils one of the mysteries surrounding krill swimming: the mechanism by which they generate lift to prevent sinking while swimming forward.
Through their experiments with Pleobot, the researchers identified a low-pressure region at the backside of the swimming legs, contributing to enhanced lift force during the power stroke of the moving legs.
Building upon this initial success, the researchers plan to continue refining and testing the designs presented in the study. Their ongoing efforts involve incorporating morphological characteristics of shrimp, such as flexibility and bristles around the appendages, into the robotic platform.
With each step forward, the team endeavors to unlock the secrets of nature, paving the way for the development of advanced autonomous underwater vehicles and enhancing our understanding of underwater exploration.