Wireless aquatic robot could clean water and transport cells
Inspired by a coral polyp, this plastic mini robot moves by magnetism and light

Date:
July 14, 2020
Source:
Eindhoven University of Technology
Summary:
Researchers have developed a tiny plastic robot, made of responsive
polymers, which moves under the influence of light and magnetism. In
the future this 'wireless aquatic polyp' should be able to attract
and capture contaminant particles from the surrounding liquid or
pick up and transport cells for analysis in diagnostic devices.



FULL STORY ========================================================================== Inspired by a coral polyp, this plastic mini robot moves by magnetism
and light.


========================================================================== Researchers at Eindhoven University of Technology developed a tiny plastic robot, made of responsive polymers, which moves under the influence of
light and magnetism. In the future this 'wireless aquatic polyp' should be
able to attract and capture contaminant particles from the surrounding
liquid or pick up and transport cells for analysis in diagnostic
devices. The researchers published their results in the journal PNAS.

The mini robot is inspired by a coral polyp; a small soft creature
with tentacles, which makes up the corals in the ocean. Doctoral
candidate Marina Pilz Da Cunha: "I was inspired by the motion of
these coral polyps, especially their ability to interact with the
environment through self-made currents." The stem of the living polyps
makes a specific movement that creates a current which attracts food
particles. Subsequently, the tentacles grab the food particles floating
by.

The developed wireless artificial polyp is 1 by 1 cm, has a stem that
reacts to magnetism, and light steered tentacles. "Combining two different stimuli is rare since it requires delicate material preparation and
assembly, but it is interesting for creating untethered robots because
it allows for complex shape changes and tasks to be performed," explains
Pilz Da Cunha. The tentacles move by shining light on them. Different wavelengths lead to different results. For example, the tentacles 'grab'
under the influence of UV light, while they 'release' with blue light.

FROM LAND TO WATER The device now presented can grab and release objects underwater, which is a new feature of the light-guided package delivery
mini robot the researchers presented earlier this year. This land-based
robot couldn't work underwater, because the polymers making up that robot
act through photothermal effects. The heat generated by the light fueled
the robot, instead of the light itself. Pilz Da Cunha: "Heat dissipates
in water, which makes it impossible to steer the robot under water." She therefore developed a photomechanical polymer material that moves under
the influence of light only. Not heat.



==========================================================================
And that is not its only advantage. Next to operating underwater, this new material can hold its deformation after being activated by light. While
the photothermal material immediately returns to its original shape
after the stimuli has been removed, the molecules in the photomechanical material actually take on a new state. This allows different stable
shapes, to be maintained for a longer period of time. "That helps to
control the gripper arm; once something has been captured, the robot can
keep holding it until it is addressed by light once again to release it,"
says Pilz Da Cunha.

FLOW ATTRACTS PARTICLES By placing a rotating magnet underneath the robot,
the stem circles around its axis. Pilz Da Cunha: "It was therefore
possible to actually move floating objects in the water towards the
polyp, in our case oil droplets." The position of the tentacles (open,
closed or something in between), turned out to have an influence on the
fluid flow. "Computer simulations, with different tentacle positions, eventually helped us to understand and get the movement of the stem
exactly right. And to 'attract' the oil droplets towards the tentacles," explains Pilz Da Cunha.

OPERATION INDEPENDENT OF THE WATER COMPOSITION An added advantage is that
the robot operates independently from the composition of the surrounding liquid. This is unique, because the dominant stimuli-responsive material
used for underwater applications nowadays, hydrogels, are sensitive for
their environment. Hydrogels therefore behave differently in contaminated water. Pilz Da Cunha: "Our robot also works in the same way in salt
water, or water with contaminants. In fact, in the future the polyp may
be able to filter contaminants out of the water by catching them with
its tentacles."


==========================================================================
NEXT STEP: SWIMMING ROBOT PhD student Pilz Da Cunha is now working on
the next step: an array of polyps that can work together. She hopes to
realize transport of particles, in which one polyp passes on a package
to the other. A swimming robot is also on her wish list. Here, she thinks
of biomedical applications such as capturing specific cells.

To achieve this, the researchers still have to work on the wavelengths
to which the material responds. "UV light affects cells and the depth of penetration in the human body is limited. In addition, UV light might
damage the robot itself, making it less durable. Therefore we want to
create a robot that doesn't need UV light as a stimuli," concludes Pilz
Da Cunha.

Video: https://www.youtube.com/watch?v=QYklipdzesI&feature=emb_logo

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


========================================================================== Journal Reference:
1. Marina Pilz da Cunha, Harkamaljot S. Kandail, Jaap M. J. den
Toonder,
Albert P. H. J. Schenning. An artificial aquatic polyp that
wirelessly attracts, grasps, and releases objects. Proceedings
of the National Academy of Sciences, 2020; 202004748 DOI:
10.1073/pnas.2004748117 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200714111728.htm

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