
New suction-cup system spins water to stick to rough surfaces - anon463637
https://newatlas.com/science/zpd-suction-rough-surfaces/
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czr
actual paper
[https://aip.scitation.org/doi/10.1063/1.5129958](https://aip.scitation.org/doi/10.1063/1.5129958)

video 1 (response measurement):
[https://aip.scitation.org/doi/suppl/10.1063/1.5129958/suppl_...](https://aip.scitation.org/doi/suppl/10.1063/1.5129958/suppl_file/video+1.mp4)

video 2 (picking up block):
[https://aip.scitation.org/doi/suppl/10.1063/1.5129958/suppl_...](https://aip.scitation.org/doi/suppl/10.1063/1.5129958/suppl_file/video+2.mp4)

video 3 (hexapod):
[https://aip.scitation.org/doi/suppl/10.1063/1.5129958/suppl_...](https://aip.scitation.org/doi/suppl/10.1063/1.5129958/suppl_file/video+3.mp4)

video 4 (human climbing tiled wall):
[https://aip.scitation.org/doi/suppl/10.1063/1.5129958/suppl_...](https://aip.scitation.org/doi/suppl/10.1063/1.5129958/suppl_file/video+4.mp4)

video 5 (human climbing concrete wall):
[https://aip.scitation.org/doi/suppl/10.1063/1.5129958/suppl_...](https://aip.scitation.org/doi/suppl/10.1063/1.5129958/suppl_file/video+5.mp4)

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keanzu
The videos are great, consumes a lot less water than I imagined. Seems like
most of the water is lost during the de-suction process, if they can scavenge
that it could really cut the water consumption down nearly to zero.

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samstave
If they have an additional ring around the outside of each cup, could they not
suction the water back into the system?

Also, wouldnt this be easily defeatable with small dowel protruding "thorns"
\- or dimples, as on a golf ball - maybe alternating convex/concave dimple
patterns? or other ridges?

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pretty_bubbles
I don't think anyone is building suction robot proof buildings yet. It can
barely climb the buildings we have now.

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NougatRillettes
My understanding of it after a quick read of the paper: you want to make a
suction cup. The usual way is with a solid cup (think plastic) with a softer
rubber-like ring around it. Near the ring, you will have atmospheric pressure
(high) outside, and vacuum pressure (low) inside, so if the ring doesn't make
perfect contact with the surface, some air is going to come in and ruin you
vacuum. What they are doing is that they are rotating a bit of water in the
suction cup, which because of centrifugal force will come close to the suction
cup frontier in a ring-like shape. This water ring will -- thanks to fluid
mechanics black magic -- have a different pressure at its exterior and its
interior. Its interior pressure will necessarily be the same as the vacuum,
and you can make it so that the pressure outside is the same as the
atmospheric pressure, hence, according to this paper, if the rubber ring fails
to make hermetic contact, air won't come in because at the frontier of the
cup, the pressure is the same both outside (atmosphere) and inside (exterior
of the water ring).

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thebiss
Does the water on the innermost edge of the rotating ring, which is exposed to
the vacuum, NOT vaporize because the absolute pressure is still above 10kPa
(100kPa atmospheric - 80kPa vacuum)? [0]

Will the seal slowly evaporate away or absorb into a porous surface like
concrete?

[0]
[https://en.m.wikipedia.org/wiki/File:Phase_diagram_of_water....](https://en.m.wikipedia.org/wiki/File:Phase_diagram_of_water.svg)

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ta1234567890
Pretty cool. Reminded me of what this guy is doing, he calls it "orthosonic
lift": [https://youtu.be/kG6vXGidQbo](https://youtu.be/kG6vXGidQbo)

Some more info:
[http://sciencechatforum.com/viewtopic.php?nomobile=1&f=77&t=...](http://sciencechatforum.com/viewtopic.php?nomobile=1&f=77&t=28698&start=0)

I believe he has a couple of patents on the technology, but not sure he'll
ever get around to making something practical with it.

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NougatRillettes
This has many of the red flags for "technological" development that won't
withstand scientific scrutiny.

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jtbayly
What flags, specifically?

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ithinkso
Author is a crackpot, judging by his posts on that forum

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raihansaputra
Quick links to diagrams explaining how it works:

[https://aip.scitation.org/na101/home/literatum/publisher/aip...](https://aip.scitation.org/na101/home/literatum/publisher/aip/journals/content/phf/2020/phf.2020.32.issue-1/1.5129958/20200113/images/large/1.5129958.figures.online.f5.jpeg)

[https://aip.scitation.org/na101/home/literatum/publisher/aip...](https://aip.scitation.org/na101/home/literatum/publisher/aip/journals/content/phf/2020/phf.2020.32.issue-1/1.5129958/20200113/images/large/1.5129958.figures.online.f6.jpeg)

(from the actual paper link from czr:
[https://aip.scitation.org/doi/10.1063/1.5129958](https://aip.scitation.org/doi/10.1063/1.5129958))

~~~
Iv
Thanks! That's a great concept!

One way of explaining it would be that instead of leaking air, it leaks
sealing water without suffering dpressurization in the process. Really neat.

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flashman
Kind of similar to the reason you'd wet a suction cup before using it: the
water helps plug any small air gaps. But in this version, a fan spins the
water and air inside the cup, with the heavier water being forced to the edge,
and any water leakage being replaced from a reservoir.

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catalogia
Is this the same mechanism as the immersion blender trick?
([https://youtu.be/TrZyuCh9df0?t=424](https://youtu.be/TrZyuCh9df0?t=424))

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Rury
No, I believe the immersion blender trick can be explained by
[https://en.wikipedia.org/wiki/Bernoulli%27s_principle](https://en.wikipedia.org/wiki/Bernoulli%27s_principle)

Whereas the suction cups in the article, use spinning water as a way to seal
suction cups on rough surfaces (the water fills in crevices of rough surfaces
I presume, allowing the suction cup to seal). The water is also spinning (i.e.
it has an inertial force) so that it counteracts the vacuum pressure in the
center of the suction cup.

~~~
jtbayly
Hmmm. At a glance I can’t figure out how Bernoulli’s law applies. The blender
trick looks very similar to the original article to me.

Could anybody explain in more detail?

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Rury
Well for one, the linked video example of the Styrofoam plates and hair dryer
(shown right before the immersion blender) is definitely due to Bernoulli's
law. See
[https://en.wikipedia.org/wiki/Bernoulli_grip](https://en.wikipedia.org/wiki/Bernoulli_grip)

As for the immersion blender, intuition should tell you that the same
principle should/or at the very least… might apply. Now it could very well not
apply (but I'm quite confident that it does). To really prove if it does or
not, one would have to do the rigorous math involved, which would include
deriving the stream function for the flow situation, verifying if conditions
allow for applying Bernoulli's principle, then applying the principle and
verifying if it matches experimental observations... This is would be non-
trivial to do (judging simply by the geometries involved) so I'm not even
going to attempt do this…

However, I’ll try explaining the gist of the idea:

Bernoulli’s principle basically states that, within a flow of constant energy,
when a fluid speeds up, it is corresponded with a drop in pressure and vice
versa. Now looking at the immersion blender, intuition (and essentially
conservation of mass) suggests that the fluid should be moving fastest between
the edges of the blender/blade and the boundaries of the container/cup (i.e.
areas where there’s very little space near the moving blender parts). Outside
these regions, intuition would suggest the fluid is moving _relatively_ slowly
(e.g. near the top of the water level in the container cup). Since the fluid
appears to move, and likely cross these regions (i.e. undergoes speeding
up/slowing down), Bernoulli’s principle states that we should expect to see a
pressure differential between these regions, where faster moving water regions
should be at a lower pressure (i.e. acting as a vacuum / suction cup).

But again, whether or not this idea is true and is valid would have to be
mathematically and experimentally verified…

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AliAdams
What about ferromagnetic fluid? You can still spin it if you are aiming to
push it 'centrifugally' into the features of the vacuum boundary, but you
shouldn't lose a lot during the detachment.

(Plus it looks much more sci-fi.)

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ambyra
Arduino controlled real live squid with water backpack. That’s the future.

I wonder if some sort of jelly would work to do the same thing, like a snail.
Or a dynamic cup surface that conforms to the wall better.

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jcims
No idea if this is actually a new idea but it's definitely new to me and I
love seeing it. What a cool concept, likely to be a few applications in
industry beyond spiderbots.

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Terr_
> The resulting inertial force generates a steep pressure gradient, allowing a
> high vacuum to be maintained at the center of the cup's vacuum zone

Sounds like a "momentum transfer" vacuum pump, shaped so that the output side
bleeds out along the rim.

[https://en.wikipedia.org/wiki/Vacuum_pump#Momentum_transfer_...](https://en.wikipedia.org/wiki/Vacuum_pump#Momentum_transfer_pump)

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jakedata
I can't say I am super looking forward to hexapod wall climbing robots.

