High-Speed Swimming Robots Use Jet Propulsion

Innovation: Academia

University of California San Diego

2019

Image: Rickard Zerpe / Flickr / CC BY - Creative Commons Attribution alone

Move in/on Liquids

Water is not only the most abundant liquid on earth, but it’s vital to life–so it’s no surprise that the majority of life has evolved to thrive on and under its surface. Moving efficiently in and on this dense and dynamic substance presents unique challenges and opportunities for living systems. As a result, they have evolved countless solutions to optimize drag, utilize surface tension, fine tune buoyancy, and take advantage of various types of currents and fluid dynamics. For example, sharks can slide through water by reducing drag due to their streamlined shape and specially shaped features on their skin.

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Modify Size/Shape/Mass/Volume

Many living systems alter their physical properties, such as size, shape, mass, or volume. These modifications occur in response to the living system’s needs and/or changing environmental conditions. For example, they may do this to move more efficiently, escape predators, recover from damage, or for many other reasons. These modifications require appropriate response rates and levels. Modifying any of these properties requires materials to enable such changes, cues to make the changes, and mechanisms to control them. An example is the porcupine fish, which protects itself from predators by taking sips of water or air to inflate its body and to erect spines embedded in its skin.

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Swimming robot from UC San Diego uses jet-propelled locomotion to move rapidly underwater.

Benefits

Flexible
Efficient
Reduced energy usage

Applications

Underwater exploration
Medical treatment

UN Sustainable Development Goals Addressed

Goal 9: Industry Innovation & Infrastructure

The Challenge

Robots are capable of moving at fast speeds, but soft robots, especially underwater, have trouble moving quickly due to the slow propagation of their components. These robots also need a constant source of energy to move and if plugged into an external power source, the cord can hinder its motion.

Innovation Details

The swimming robot mimics the method of jet propulsion that cephalopods such as squids use to move through the water. The robot has a pressure chamber controlled by springs that periodically fills with water to inflate, and then releases the water to deflate. The water rushes through a nozzle during deflation, propelling the robot forward. When the robot repeatedly deflates, it reaches a certain thrust frequency, making the robot move smoothly and efficiently. The robot is also made of smart materials that camouflage the robot as it moves about.

Biological Model

Cephalopods such as squids swim by jet propulsion. They expel water through a moveable tube called a siphon, which jets them in the opposite direction.

See Related Strategy

an orange cuttlefish with a dark background at the lisbon oceanarium

Biological Strategy

Siphon Directs Underwater Movement

Octopods

Siphons of octopi, squid, and cuttlefish jet through the water with directional control via jet propulsion.

References

Journal article

Fluid-structure investigation of a squid-inspired swimmer

AIP

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