Leaky pipes can be better for moving water | Hacker News Reader

Leaky pipes can be better for moving water

nature.com

179 pointsrehto2157 comments

Very neat concept. Love to see biomimicry in action. More great stuff available at https://biomimicry.org/.

And for anyone wondering — these pipes don't leak water, they leak air and other gasses. Title is a tad bit confusing.

There possibly is great stuff there, but after having dismissed the third popup in roughly as many seconds, I gave up and hit the back button.

I've no idea why websites do this. No one wants it.

Those 3 clicks to close the popups probably were seen as more "engagement". ;)

Wasn't sure why they called biology "chaotic". Complex, yes, but chaotic? No. More like "we don't understand it".

“Chaotic” may be an appropriate term. I mean, “Chaos Theory” (using a very technical definition of the word “chaos” which is only serving as an analogy here) deals with systems that are understandable and somewhat predictable in the near term but with a certain amount of a particular kind of complexity that makes it totally unpredictable in the long term. Even when you understand that he fundamental, reductionist physics. A simple pendulum is predictable over the near and far term. A double pendulum, on the other hand, is “chaotic,” and fundamentally not predictable in the long term, even though all the relevant fundamental physical laws are known.

I think “chaos” is a good word describing something which is in between the fully predictable and the purely random.

Highly misleading title. Content was interesting, but they never said this was "better for moving water". Rather, they said this was better for heat and gas exchange with water...

Is 3d printing a 1mm wide cube really something you need "one of the most advanced" 3d printers for? Can't we get better resolution than that with hobby grade hardware?

>Is 3d printing a 1mm wide cube really something you need "one of the most advanced" 3d printers for?

Absolutely! fine features and sharp edges are extremely hard.

This is also a fundamental mischaratization of the scale they are working at, as object size /= feature size. the analogy would be images vs pixel. In this case, the image is 1mm, not the pixels

I dont have the paper, but the video shows features around 0.25 mm and a x-y resolution of 0.025mm

If you're willing to print slowly, those are not notable specs. A $250 Ender has an XY resolution of 0.01mm and 0.15mm nozzles are common.

I’m not sure, but I’d bet that this is a debate over precision Vs accuracy.3D printers can be pretty precise in relative terms, but they are difficult to make accurate. Extruder style printers struggle with small feature size because the heating and cooling distorts from the reference size. .01mm resolution does not mean you accurately achieve .01mm parts. It means your machine can be commanded to make .01mm moves and will make them repeatably.

That said, 3D printers aren’t bad. Small parts are just difficult.

It looks like feature size is roughly 0.2mm. This is achievable with hobby grade printers.

Even though the video shows an FDM printer, these look like resin prints. Resin printers tend to have better resolution.

I might be able to print this with my Ender 3, but I bet a resin printer would do better.

I wonder whether there would be any capillary action on the resin during printing, potentially ruining the print?

My friend has a secondhand dental resin printer - feature size is 0.075mm. Seems like he could make this structure at a significantly smaller scale than pictured in the video.

But it's the most expensive machine that goes "Bing!" in-case the director walks by.

My Prusa can print a 1mm cube. Is the complaint that the resolution of hobby machines aren't good enough or that it's using a thermonuclear rocket launcher to squash an ant?

Im assuming you mean your Prusa can print a solid 1mm cube with rounded edges, which is very different than a lattice structure with an overall 1mm size

Absolutely. Then no. :)

I wish I had a 4000 lasers plaid-mode FDM printer able to work in titanium, PLA, ASA, styrofoam, carbon nanotubes, steel, copper, wood, concrete, borosilicate, and EPDM at micrometers.

What flow rates can this achieve and sustain? If you want to use it for absorption of gasses or heat, presumably you are going to want to move that heat and gas somewhere.

Diffusion is quite slow, so I expect you would need flowing water. It might not be all that valuable to have that surface area if you can't also move the water around.

I imagine you could have many of these cubes with water flowing past one of their faces. Essentially using Diffusion to move stuff 1mm and using flow once the water is in a real pipe.

It can sustain a flow rate of 0.

Why 0? If you remove the substance at the end point (e.g. water evaporation by trees) you should have a non-zero flow.

I imagine any significant flow would cause turbulence and surface movement, causing the surface tension to break.

If you watch the video you can see that that does not happen.

Interesting, the principles presented in this video seem microfluidic but it also relies on the surface tension of water so I wonder wonder what realm this belongs under.

It belongs under microfluidics. I don’t understand like you would make it sound like that field doesn’t deal with surface tension of water, that’s one of the most central elements of microfluidics.

Neat... But it's really just the same as putting some tissue paper in water and watching the water absorb up the tissue...

Super advanced 3D printing...

My mother would buy a sponge instead.

Really neat! Heat pipes also utilize capillary action (via wicks) for heat exchange: https://en.wikipedia.org/wiki/Heat_pipe

Where does the potential energy that the water gets when moving up come from?

Adhesion.

The water molecules are attracted to the surface of the structure by adhesive forces. This means that when the water molecules are away from the structure, there is "potential adhesive energy". As the water moves closer to the surface, the "potential adhesive energy" is reduced and turns into gravitational potential energy -- until at some point an equilibrium is reached. The more surface area the liquid can adhere to, the higher it can rise.

If this is hard to understand, think of two strong magnets, one lying on a table, and one mounted at a point somewhere above the table. When the two magnets are not touching, there is potential magnetic energy. If you bring the top magnet low enough, at some point the bottom magnet will be pulled up towards the other magnet until it touches, increasing it's potential gravitational energy and minimizing its potential magnetic energy.

Kinda guessing, but I'd assume from temperature - i.e. chaotic (a.k.a. brownian) motions of the particles resulting in them randomly getting close enough to the enclosure's walls that the surface tension (which from what I see on Wikipedia seems to be basically electric attraction of particles) "glues" them to the wall, and/or to particles that got already "glued" to the wall just moments before. I would suppose "in real life" the resulting cooling is probably basically irrelevant and gets immediately "replenished" from the surroundings, and (again also from what Wikipedia seems to say) the equilibrium seems to be reached vs. gravity, presumably mostly of the "non-glued to walls" part of the water column. I.e. I guess when the freeriding bunch of suckers in the middle of the column pull you down more than the sweet, sexy wall pulls you up... errr, I mean, the sum of the gravity force acting on the water molecules in the middle of the water column equals the sum of the wall-sticking force of all the wall-sticking water molecules (distributed locally through the water-to-water-sticking force of the water molecules).

The energy comes from the work done when the surface of water was broken, plus the already existing kinetic energy of the water, and the localized energy in the wall of tube. (Basically getting the surface of the tube wet is energetically more favorable than not, so this means there's a hidden/latent energy there.)

As others mentioned it's ultimately mediated through EM forces between molecules. ( https://en.wikipedia.org/wiki/Capillary_action )

My highly uneducated guess on this would be that the water molecules moving up are cooling down a tiny little bit.

Being cooler would then be making it unable for them to climb further when a certain threshold is reached, meaning they would need the surrounding environment to heat it up a little again to allow it to move further.

Cohesion-tension I think.

What was the main difficulty, here?

It's neat, but I'm not seeing the novelty. Is it the mm-scale capillary action, or the fact that it was done with 3D printing?

"Yes."

The best we've been able to do for capillary action so far has been through machining (e.g. fountainpen feeds) which has no real internal structure and will happily leak all over the place it touches something else, or sintering, which has a microstructure that takes forever to do its thing.

Huh, I guess this one of those “it looks easier than it is” things. Cool! Thanks for the explanation.

being able to create true, 3d cappilary volumes? Ridiculously hard.

Speaking of mixing water and gas, I’ve got about a dozen ideas for new designs for humidifiers. Should I pursue that? Patents and such?

Why are they better?

Well there would be no filter medium to harbor mold or to replace. And with ultrasound it puts minerals and bacteria into the air somewhat. My designs really on natural evaporation with easily cleanable parts.

Once niche market familiar with is cigar humidifiers. Mold is a constant concern and all of the solutions on the market today either use ultrasound which works great, but causes the problems you mentioned or silca beads, which are much more cumbersome to work with.

Anyone have an STL or OpenSCAD of this?

Is this making use of Bernoulli's principle to avoid busted pipes? Small holes in the pipe when water is running would not leak since σ > p for high speeds and small area. When water is not running, the water leaks out due to increased pressure and avoids potential busted frozen pipes. Although I don't see how this maintains water quality if the pipes are underground.

Frozen underground pipes are rarely a problem. The temperature underground rapidly approches ~15°C independently of the current weather. So no need to make holes in your underground pipe :)

True! So I wonder how this works for above-ground pipes. If the water is sitting in some U-pipe would it not just leak out because its velocity is zero? Or are the holes so small that the σ > p even at rest?

The pipes described here do not leak water: the holes are so tiny that the surface tension does not let water spill out. They let air molecules reach the water though.

In the abstract they mention how this could be useful in cooling systems and such (iow, you are unlikely to use this for drinking water).

They will leak chlorine or iodine gas from water if that's used for disinfection.

Assuming something won't get into water via the pores...

Even in a cooling system contamination can be a problem regardless of how good the biocide is.

Could this be used to transport water long distances like an aqueduct?

Basically, a paper towel, sponge, wick, or most any woven fabric.

I bet the ‘3D microstructures’ in a typical woven super Shammy are smaller.

Slow day at the lab? Publish or perish, I suppose.

The point here is that you can build complex 3D structure to have an exchange surface with gases bigger of orders of magnitude than with a sponge or a towel.

I thought the bigger point was that they could control the cells that liquids seep through.

If your goal was to soak up the most liquid for the least cost then paper towels seem like a superior solution.

This innovation looks like it’s superior when you have goals like “put 1 cm saw of water in this exact path”

Anq then a sinkhole happens

And also:

Giardia

Legionella

Norovirus

Shigella

Campylobacter

Copper

Salmonella

Hepatitis A

Cryptosporidium

E. coli, excess fluoride (tie)

https://www.cdc.gov/healthywater/drinking/public/water_disea...

Copper?

At high levels copper is toxic. USEPA requires drinking water systems to test for copper at endpoints.

Sure, but how would this kind of pipe promote the formation of copper?

Bioavailable copper, I assume.

Copper pipes should scale over.

The mention of capillary action reminded me of hydro. Would be great for small scale energy production/storage.

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