New ‘squidbot’ explores coral reefs using jet propulsion

A new robot, created by researchers from University of California San Diego, mimics squids by propelling itself with jets of water that it generates with its flexible elastic body. It is hoped this new design could revolutionise coral reef monitoring.

The squidbot on display during a test run in an aquarium tank

As we seek to better explore our oceans and learn more about the creatures that live below the surface, underwater robots can play a crucial role by helping us overcome some of the limitations we face. They are capable of withstanding the crushing pressures of the deep sea, accurately taking multiple-measurements at once, collecting samples and even autonomously operating themselves using advanced AI systems. All while researchers reap the rewards from the surface. Yet there are still many improvements to be made, such as the progression of ‘soft robots’ designed to minimize their impacts whilst surveying vulnerable ecosystems like coral reefs. In an attempt to do this researchers from UC San Diego have designed a new soft robot, known as the ‘squidbot’, by taking inspiration from the cephalopods that have mastered the art of soft body swimming.  

Soft sentinels

The original idea behind the squidbot was to create a new type of underwater robot capable of exploring coral reefs whilst reducing its impact on the animals that live there. To do this meant creating a soft robot made from flexible materials, such as acrylic polymers, with as few solid pieces as possible. This reduces the damage they cause to the fish, corals, crustaceans and other creatures on the reef, whilst maximising what they can help researchers learn about these vital ecosystems. However, the problem is that soft robots is that they are notoriously slow and hard to manoeuvre due to their lack rigidity. This meant that the team had to create a method of locomotion in these soft robots which allowed them to move more efficiently. To do this they decided to look at squids, who despite their own soft bodies are still capable to shooting themselves around the sea at high speeds.

Invertebrate inspiration

The secret to the squid’s soft swimming success, is a form of locomotion known as jet propulsion. To do this the squids fill their mantle cavity with water and then expel it through a specialised funnel (known as a siphon) by contracting their elasticated mantle walls. This technique allows squids to achieve the top speeds of any aquatic invertebrates. In their new research paper, recently published in the journal Bioinspiration & Biomimetics, the team from UC San Diego has shown that it can be replicated in soft robots. Their squidbot, made predominantly from flexible acrylic polymers with a few hard 3D-printed components, mimics the squid’s adaptation with a simple yet effective design.

The squidbot prototype alongside a researcher during its trial run

Shaped roughly like a paper lantern, the squidbot consists of a cylinder of flexible ‘ribs’ supported by elasticated ‘skin’ which are connected to a circular plate at either end. At one end a nozzle allows the chamber to fill with water, before an on-board power system causes the ribs to contract forcing the water back out of the nozzle. This continues in a repetitive cycle that allows the robot to achieve a speed of 18-32 cm/s, making it by far the fastest soft robot to date. “Essentially, we recreated all the key features that squids use for high-speed swimming,” says UC San Diego professor and study author Michael T. Tolley, in a recent press release. “This is the first untethered robot that can generate jet pulses for rapid locomotion like the squid and can achieve these jet pulses by changing its body shape, which improves swimming efficiency.”

Tried & tested

After testing the jet propulsion system in the lab, the team decided to really see what the squidbot could do by releasing a prototype into an aquarium tank at the Scripps Institute for Oceanography. This experiment (which you can see in the video below) showed that the squidbot was able to explore the tank untethered and without incident, whilst also being able to control its direction with its nozzle. There is still some work to be done and the researchers believe they can increase its efficiency and get it moving even faster, but it will hopefully soon get its chance to explore a real coral reef. The final version will also be able to carry an underwater camera or other form of sensor that will allow it to record important information as it jets its way across the reefs. It is hoped that in time these soft cephalopod-inspired robots could eventually be used as remote sentinels on coral reefs and provide an early warning for things like coral bleaching, pollution and overfishing.

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