Building Swimming Robots with Help from Bacteria

As robots are required to complete increasingly complex tasks in harsh environments, a new field of robotics research is emerging, taking inspiration from an unlikely source.

A new trend in robotics research is emerging. Just as robots are asked to complete increasingly complex and intricate tasks, they are expected to do so in increasingly diverse environments. To achieve this, researchers are developing reconfigurable robots that are able to dynamically adapt their structures to accomplish their tasks. These are the new ‘soft’ robots.

Dr. Federico Renda, Assistant Professor of Mechanical Engineering, envisions two kinds of modular soft robots: a novel underwater locomotion and manipulation mechanism based on a multi-flagella paradigm, and a versatile soft robotic manipulator based on reconfigurable modules.

“Soft robotics is a new branch of robotics that deals with highly deformable robots made primarily of soft, compliant material, like elastomers,” explained Dr. Renda. “The main driver is the search for advanced robots capable of intervention in unstructured environments. This includes human-robot physical interaction and can be called ‘the mechanical side of artificial intelligence.’ Oil and gas infrastructure surveillance and maintenance, and natural ecosystem monitoring, are a few areas that could benefit immensely from soft robots.”

The research project aims to develop innovative solutions for robotic locomotion and manipulation by combining the positive assets of both fields, providing robust, adaptable, dexterous, safe, and low-cost robotic solutions.

“Locomotion and manipulation are the main types of physical interactions any robot should be able to perform in its environment,” said Dr. Renda. “Nowadays, robots are required to navigate and intervene on-shore as well as in the air, or even in space, and underwater.”

Dr. Renda’s team has developed a prototype designed to achieve safe and reliable interaction with the environment, including delicate eco-systems and expensive industrial installations such as ship hulls and oil pipelines.


The research team took their inspiration from bacteria like E. coli, C. crescentus and others for a flagellum-inspired soft underwater propulsor – a mechanical propulsion device – exploiting passive elasticity. A flagellum is a slender threadlike structured appendix enabling many bacteria and protozoa to swim. The team believes the multi-flagella approach to movement can give the necessary support and intrinsic safety required to overcome the challenges imposed by underwater robotic applications.

“The inspiration for our approach came from bacteria, particularly for the propulsor topology and actuation unit. However, the actual design has been adapted to cope with the change in scale and enriched to include propulsion and manipulation capabilities within the same device,” said Dr. Renda.

Flagellated microorganisms are considered excellent swimmers given their size – combined with the simplicity of their actuation and the richness of their dynamics, they are a valuable source of inspiration for the design of self-propelled underwater robots.

“The main benefit of our approach is that we are able to combine the advantages of a traditional propeller – which employs a simple actuation mechanism – with soft-bioinspired robots that are easily maneuverable, noiseless and safe, potentially giving rise to a novel class of underwater robots able to effectively navigate the ocean world,” explained Dr. Renda.

The robots are designed as a passive system, capable of moving in a range of geometrical configurations from the interaction with the surrounding fluid. Essentially, the motor rotates a straight flagellum which deforms in a helical shape (forming helical traveling waves) due to its flexibility in the fluid, thrusting the robot forwards.

The robots will be equipped with high resolution cameras, sophisticated sensors, and multiple flagella to provide robust, adaptable, and reconfigurable operations. Each flagellum is capable of performing both grasping and propulsion, with the propulsor mechanism bio-inspired by prokaryotic bacteria, which sport a vast repertoire of swimming strategies to enable efficient propulsion.

“Of special interest is the chance to exploit passive structural response and the ensuing kinematics of a flagellum-like body,” added Dr. Renda. “This unique feature, coupled with the capability of performing basic manipulation could make our flagellum-inspired systems a class of soft robots especially suited for intervention and inspection of marine ecosystems, industrial installations, and fluid-filled conduits of diverse size and fluid composition.

“Virtually any industry operating in an underwater environment could benefit from the results of this research, as the demand for safe and reliable underwater manipulation is high and not reasonably addressed by current technologies.”

Jade Sterling
News and Features Writer
30 May 2019