Jellyfish-like robots could one day clean up the world's oceans

Date:
April 25, 2023
Source:
Max Planck Institute for Intelligent Systems
Summary:
Roboticists have developed a jellyfish-inspired underwater robot
with which they hope one day to collect waste from the bottom of
the ocean.

The almost noise-free prototype can trap objects underneath its
body without physical contact, thereby enabling safe interactions
in delicate environments such as coral reefs. Jellyfish-Bot could
become an important tool for environmental remediation.


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FULL STORY ==========================================================================
Most of the world is covered in oceans, which are unfortunately highly polluted. One of the strategies to combat the mounds of waste found
in these very sensitive ecosystems -- especially around coral reefs --
is to employ robots to master the cleanup. However, existing underwater
robots are mostly bulky with rigid bodies, unable to explore and sample
in complex and unstructured environments, and are noisy due to electrical motors or hydraulic pumps. For a more suitable design, scientists at
the Max Planck Institute for Intelligent Systems (MPI-IS) in Stuttgart
looked to nature for inspiration.

They configured a jellyfish-inspired, versatile, energy-efficient
and nearly noise-free robot the size of a hand. Jellyfish-Bot is a collaboration between the Physical Intelligence and Robotic Materials departments at MPI-IS. "A Versatile Jellyfish-like Robotic Platform
for Effective Underwater Propulsion and Manipulation" was published in
Science Advances.

To build the robot, the team used electrohydraulic actuators through which electricity flows. The actuators serve as artificial muscles which power
the robot. Surrounding these muscles are air cushions as well as soft and
rigid components which stabilize the robot and make it waterproof. This
way, the high voltage running through the actuators cannot contact the surrounding water. A power supply periodically provides electricity
through thin wires, causing the muscles to contract and expand. This
allows the robot to swim gracefully and to create swirls underneath
its body.

"When a jellyfish swims upwards, it can trap objects along its path as
it creates currents around its body. In this way, it can also collect nutrients.

Our robot, too, circulates the water around it. This function is useful
in collecting objects such as waste particles. It can then transport the
litter to the surface, where it can later be recycled. It is also able to collect fragile biological samples such as fish eggs. Meanwhile, there
is no negative impact on the surrounding environment. The interaction
with aquatic species is gentle and nearly noise-free," Tianlu Wang
explains. He is a postdoc in the Physical Intelligence Department at
MPI-IS and first author of the publication.

His co-author Hyeong-Joon Joo from the Robotic Materials Department
continues: "70% of marine litter is estimated to sink to the
seabed. Plastics make up more than 60% of this litter, taking hundreds
of years to degrade. Therefore, we saw an urgent need to develop a robot
to manipulate objects such as litter and transport it upwards. We hope
that underwater robots could one day assist in cleaning up our oceans." Jellyfish-Bots are capable of moving and trapping objects without physical contact, operating either alone or with several in combination. Each
robot works faster than other comparable inventions, reaching a speed
of up to 6.1 cm/s. Moreover, Jellyfish-Bot only requires a low input
power of around 100 mW.

And it is safe for humans and fish should the polymer material insulating
the robot one day be torn apart. Meanwhile, the noise from the robot
cannot be distinguished from background levels. In this way Jellyfish-Bot interacts gently with its environment without disturbing it -- much like
its natural counterpart.

The robot consists of several layers: some stiffen the robot, others
serve to keep it afloat or insulate it. A further polymer layer functions
as a floating skin. Electrically powered artificial muscles known as
HASELs are embedded into the middle of the different layers. HASELs
are liquid dielectric-filled plastic pouches that are partially covered
by electrodes. Applying a high voltage across an electrode charges it positively, while surrounding water is charged negatively. This generates
a force between positively-charged electrode and negatively-charged water
that pushes the oil inside the pouches back and forth, causing the pouches
to contract and relax -- resembling a real muscle. HASELs can sustain
the high electrical stresses generated by the charged electrodes and
are protected against water by an insulating layer. This is important,
as HASEL muscles were never before used to build an underwater robot.

The first step was to develop Jellyfish-Bot with one electrode with
six fingers or arms. In the second step, the team divided the single
electrode into separated groups to independently actuate them.

"We achieved grasping objects by making four of the arms function as a propeller, and the other two as a gripper. Or we actuated only a subset
of the arms, in order to steer the robot in different directions. We
also looked into how we can operate a collective of several robots. For instance, we took two robots and let them pick up a mask, which is very difficult for a single robot alone. Two robots can also cooperate in
carrying heavy loads. However, at this point, our Jellyfish-Bot needs
a wire. This is a drawback if we really want to use it one day in the
ocean," Hyeong-Joon Joo says.

Perhaps wires powering robots will soon be a thing of the past. "We aim to develop wireless robots. Luckily, we have achieved the first step towards
this goal. We have incorporated all the functional modules like the
battery and wireless communication parts so as to enable future wireless manipulation," Tianlu Wang continues. The team attached a buoyancy
unit at the top of the robot and a battery and microcontroller to the
bottom. They then took their invention for a swim in the pond of the Max
Planck Stuttgart campus, and could successfully steer it along. So far, however, they could not direct the wireless robot to change course and
swim the other way.

* RELATED_TOPICS
o Plants_&_Animals
# Sea_Life # Marine_Biology # Fisheries
o Matter_&_Energy
# Robotics_Research # Engineering # Vehicles
o Earth_&_Climate
# Energy_and_the_Environment # Water #
Environmental_Issues
o Computers_&_Math
# Robotics # Artificial_Intelligence # Neural_Interfaces
* RELATED_TERMS
o Jellyfish o Artificial_reef o Dinoflagellate o Robot o
Octopus o Robot_calibration o Friction o Coral_reef

========================================================================== Story Source: Materials provided by Max_Planck_Institute_for_Intelligent_Systems. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. Tianlu Wang, Hyeong-Joon Joo, Shanyuan Song, Wenqi Hu, Christoph
Keplinger, Metin Sitti. A versatile jellyfish-like robotic platform
for effective underwater propulsion and manipulation. Science
Advances, 2023; 9 (15) DOI: 10.1126/sciadv.adg0292 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/04/230425111232.htm

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