New lubricated mussel-proof coating | Hacker News Reader

New lubricated mussel-proof coating

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This sort of anti-fouling is the holy grail.

Copper based anti-fouling goes back centuries. The USS Constitution was copper bottomed in 1794.

https://ussconstitutionmuseum.org/2015/08/12/copperbottomed/

I remember an NPR story about using extremely hot peppers (adding capsaicin to bottom paint) to defoul.

There was an anti-stick bottom paint but the trouble with it was that it wouldn't stick to hull.

The trouble with copper is that it's a biocide, it kills. You're basically putting poison on the bottom of your bottom which leaches into the soil. Like tributyltin, copper's days are numbered.

It's a hard problem. When I get back into sailing, it'll be dry sailing (put boat in water and haul out when done). BTW, bottom jobs are freaky expensive, $10,000 for a race bottom every year.

Indeed, copper sheathing [0] may have been used by the ancient Phoenicians and Carthaginians, but the first authenticated use seems to have been in 1758 [1].

[0]: https://en.wikipedia.org/wiki/Copper_sheathing

[1]: https://darchive.mblwhoilibrary.org/bitstream/handle/1912/19... (pdf)

When you pull your boat out, make sure you rinse your bilge and motor (if any) before leaving to prevent the spread of Zebra Mussels. They've just arrived at the Central Texas lakes and it's only a matter of time before they become an expensive problem like they have elsewhere.

I've always wondered why they don't use some kind of peel-off adhesive layer. Would the mussels just penetrate through it and still cement to the hull? Even if you made it easy for them to cement to the adhered layer?

I know boat owners would be happy about this(not just sail boats). If it could last. Diving and scrubbing is a pain in the butt even when you dont mind diving.

Any idea how long this coating would last on a ship's hull?

A competitive racer will get a bottom job once a year and dived (cleaned) every other week. It can last 2 or 3 years with regular diving.

BTW, this is a great application for underwater drones both for big ships and littler sailboats.

"Copper = poison" is an oversimplification. Copper is also an important mineral, with 2mg/day a rough guideline for human consumption: https://ods.od.nih.gov/News/Copper.aspx (That number is at the very end, and that link also contains other interesting details about it.)

It's not like lead, where basically every atom of it in you or the ecosystem is doing no good.

NB copper is pretty notorious for killing sea life. It's fine for fish and mammals, but a very small amount can kill all the algae and non-fish critters in an aquarium. Old timey copper submarine wires killed life for a fair radius on either side when they broke down.

Most sea life just isn't capable of dealing with anything more than trace amounts of copper. When paint flakes or is scraped off the chips could have really negative local effects.

That's humans. Are lower animals (and plants, and bacteria) the same, or is copper more like lead to them?

Well, considering our bodies all eventually end up feeding lower animals, plants, and bacteria, it can't be that fatal to them.

Edit: If you want way too much detail in answer to your question: http://www.chemet.com/assets/1/6/Copper_and_the_Ocean_Enviro... The most relevant bit is probably this bit on the bottom of page 5 and into page 6: "A study was performed to determine if pen-raised salmon were bioaccumulating copper from the antifouling coatings on the pens (20). Five pens were used - three of which were treated with cuprous oxide containing antifouling coatings and the other two were left untreated. The concentrations of copper in the muscle and liver of the salmon were measured, Figure 7. It was found that there was no correlation to pen treatments. It was speculated that the reason for this is the leaching of the copper was sufficiently slow such that the natural homeostasis of the fish and their detoxification processes are not compromised and that the leached Cu ion is reduced by complexation with organic and inorganic substances in the seawater."

It isn't clear to me if these "pens" were enclosed or not; if they were then there really doesn't seem to be much reason to worry about copper antifouling.

The article also says "Copper is an essential element required for normal growth in all plants and animals. As such, it is considered a normal constituent in the ecosystem in both soil and water where its presence is partially due to the metabolic by-products of plants and animals as previously discussed." The oceanic concentration of copper is given as 0.25ppb, which comes out to 340 million metric tons of copper in the oceans overall. I suspect that, like many do with "radiation", we tend to casually assume the normal concentration in the world is zero, thus rendering any human addition to the world an infinite-percent increase, but the natural world is messier than that.

I thank you for your question, the research was interesting.

Almost any compound is poisonous in high concentrations and/or doses. Even water can be deadly if one drinks too much over too short a period.

https://en.wikipedia.org/wiki/Water_intoxication

In the context of discussing putting something into the ocean, using the example of "lots of water" being toxic is somewhat... amusing.

Given that copper is unambiguously a nutrient for life, I'd like to see a mechanism for how it would be excessively concentrated in places other than where it is directly being used before I get too concerned. In general, "in the ocean" is what I'd reach for as my example of where it is very difficult for something water-soluable to end up concentrating unexpectedly.

Copper is something we put in multivitamins, on purpose. You can buy copper supplements for your cattle: https://www.jefferspet.com/products/copasure You can read about how to rectify copper deficiencies in your garden soil, as well as the signs you've got too much: https://www.gardeningknowhow.com/garden-how-to/soil-fertiliz... "Copper = poison" is an oversimplification, in a way that "Lead = poison" isn't.

Since the subject of context has come up - in the context of water-living invertebrates, copper is poisonous in anything other than very low concentrations. This is why copper containing solutions are used to kill snail and slug infestations in aquariums, gardens and elsewhere.

Not sure why there is any confusion about this. Any aquarium keeper for example, knows to avoid copper religiously if keeping inverts.

Yes, tomatoes are poisonous (a relative of the nightshade) but you'd sooner drown in all the tomato juice you'd have to consume.

I think the vines and leaves are the parts to worry about, but even then it's not as bad as the more toxic members of the nightshade family.

This comment comes up in every thread like this. What's the point?

> "Large accumulations of mussels can weigh as much as 1,700 pounds per square foot."

I really find it hard to believe that is a number based in reality.

Disclaimer: I am no expert!

EDIT: Even if the mussels were solid gold and it was a cubic foot of them, they would "only" weigh 1206 pounds.

source: http://www.coolmagnetman.com/magconda.htm

A little digging around suggests 35kg per square meter is a more reasonable estimate[1], which is about 8lbs per sqft. I suppose it's possible some measures include the weight of the water in the mussels, and others don't?

1: https://www.boatdesign.net/threads/boat-weight-increase-due-...

That's ignoring the buoyancy from displacing water and only covers two years. I could see the worst case say a stationary house boat being vastly more problematic over 30+ years. But, they should generally fall off before the weight gets crazy.

It does seem hard to believe, perhaps they mean a square foot of mussels on a boat bottom causes drag equivalent to towing an extra 1700lbs?

I wonder if the author is confusing weight with drag. I could see mussels (and the algae they always bring with them) introducing more drag on the hull than their weight. But then again, I'm no expert, just a weekend sailor.

I had a mental image of a foot square patch of hull with a 200m long spire of mussels sticking off the side.

I'm pretty sure that's a typo in the article.

"It's weird. The chart says depth here is 200m, but we always bottom out."

Yeah, that's just a crazy number. It would be a crazy number if mussels were made of lead.

I'm guessing it is a typo of some form. One (or perhaps both) of the unit values are wrong. It doesn't takeaway from the fact that mussels are a huge issue, or the amazing way they have adapted to attaching themselves to surfaces.

Find a way to harvest the mussels and you'll need no food delivery at sea. /s

perhaps the square foot is only the footprint of the accumulation of mussels? They could extend out a pretty long way..

I just assumed cubic feet

Even a cubic foot of water would be well under 100lbs. I doubt a cubic foot of mussels + water to fill the rest could weigh a ton.

It may be possible for (especially stationary structures) to accumulate enormous columns of biofouling materials, but for such a layer to reach > 20 feet thick (possibly closer to 50 feet without counting the interstitial water) sounds unreasonable. But I'm not knowledgable in this area.

Paper:

http://science.sciencemag.org/content/357/6352/668

DOI: 10.1126/science.aai8977

It doesn't seem to contain the 1700 lbs per square foot number (it just mentions pull-off energy in the order of 1J/m^2).

And linked article, originally hosted at harvard.edu (what's with these websites just copying articles and hosting them themselves??):

https://news.harvard.edu/gazette/story/2017/08/wyss-develope...

(Unrelated, to hell with those popups that trigger when your mouse leaves the window. To hell with them I say!)

Barely anything sticks to HDPE, has that ever been tested?

HDPE and PTFE (teflon) both have very interesting self-lubricating qualities; their surfaces act almost like they are somewhat liquid, not unlike ice. They're not nearly as good as SLIPS but they have similar properties. I don't know if it's true but the way I've heard it explained is that PTFE and HDPE are so long-chained that loose molecule ends act kind of like hairs on the surface. The hairs can slip over each other very easily, so they act somewhat like a liquid.

But in reality HDPE is specifically used to grow mussels on: http://www.plasticsnewseurope.com/article/20131011/PNE/31011...

Isn't the HDPE only used as flotation devices to hang culture ropes from ?

If not, I've got another project I'll never do: Figure out how mussels adheres to HDPE and make revolutionary paints and glues for it!

Mussels use byssus threads, which are a keratin+polyphenolic protein core coated in an adhesive protein mix. The keratin/polyphenolic core provides the strong part, then the adhesive obviously adheres it. Both parts are very important, and I imagine it'd be hard to have the adhesive work well by itself.

The process of creating the threads also seems relatively difficult, but Google seems to have some byssus-based adhesives. Who knows, maybe you'll end up with something interesting.

Particularly this, seems like it might not be too difficult to make at home with some equipment and knowledge: https://www.livescience.com/6974-glue-derived-clinging-musse...

I never thought I would see the day ;)

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