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Self-healing material can build itself from carbon in the air (mit.edu)
279 points by extraterra 5 months ago | hide | past | web | favorite | 82 comments

What stops the thing from growing indefinitely, but also fast enough when damaged to return to the "original" state?

If there's a "surface coating" which when damaged, causes the "inside" to "grow" again, how does the coating repair itself, to stop the "inside" from growing beyond the original surface?

With trees and porous materials, this is known as "wicking". With humans and biology, it's the clotting factor that prevents bleeding out. There are downsides to this as well, blood clots in veins and arteries can cause heart attacks, strokes.

I read about this recently and found it fascinating - specifically related to tree height, but alludes to other implications.


It can't grow indefinitely, because the reaction with the carbon consumes the reactant in the material itself. I suspect the surface coating is a bit like the layer of aluminium oxide that forms on the surface of aluminium in that it seals off the mass under it from reacting with the air, and when scratched, the material underneath reacts with the carbon in the air to form a new coating.

proto-molecule ? :)

Can these surfaces "get cancer"? As in, for some reason, the reaction continues way beyond simply healing the crack?

Cancer is unregulated growth. Since the authors are moving towards non-biologically derived catalysts, there will be no life-derived chloroplasts like they are currently using. So, you're asking can a non-biologically derived material spread indefinitely beyond the filling in of small cracks in its surface? I don't think there's a risk of that based on the article. Is there another non-biological material that spreads in the manner you've described?

I think cancer is a more specific concept than just "unregulated growth." Cancer is a phenomenon that occurs when a valid "self-replicate then die" program has a similar encoding to a "self-replicate indefinitely" program, such that random-noise damage to the program's stored representation can result in the former being rewritten into the latter.

Whether or not the substrate is biological, I would think that you'd still have to worry about ensuring your program is encoded in such a way that the part of it that turns it off can't be damaged without disabling the program as a whole.

Hope not - otherwise an alien civilization might find us someday with everyone frozen in carbonite like Han Solo.

I wonder how efficient it is. If a square meter of the material were to be placed in 1000w/m² sunlight, how many grams of carbon can it scrub per hour? Can the carbon be easily recovered? How many break/repair cycles can this material do without deforming or degrading?

If this material can convert carbon much more efficiently than plants, it would indeed be a game changer.

Plants are essentially limited by one particularly slow enzyme. There are currently research efforts aimed at fixing that enzyme to make plants much more efficient.


unlikely imo. rubisco has been studied intensely for decades without making much headway. furthermore, the evolutionary pressure for an improved rubisco is so immense that if it were possible we'd probably see it in nature.

>furthermore, the evolutionary pressure for an improved rubisco is so immense that if it were possible we'd probably see it in nature.

I disagree with this logic, as one could apply it to any theoretical biologic feature. The fact that random-walking evolutionary processes haven't stumbled upon a more optimal solution has nothing to do with whether such a solution exists or is easy to find.

Specifically, the gradient crawl that evolution gives must yield viable organisms among every step. If something is within a local maxima that cannot be climbed out of while remaining viable, then evolution can't do anything by definition. That doesn't mean that a better global maxima doesn't exist, and an organism engineered to a better state.

On the other hand, organisms are generally very "fault tolerant" systems in the small—if you get a crucial gene copied, and then one of the copies mutates to do something weird while the other remains functioning, the resulting organism is probably going to be viable, since the weird thing that the mutated copy of the gene does will [unless it's some very specific type of "weird thing" it's producing] be treated by the body as just another foreign enzyme to xenometabolize or foreign antibody to attack.

And the organism's genetic line can persist with that mutant gene indefinitely, building onto it until it becomes a useful feature.

(This isn't so true in especially small organisms, where an extra gene here and there might blow their size or resource budget. This is one of several things constraining the evolution of mitochondria, for example.)

In such incredibly high-dimensional landscapes, such a thing as "local maxima" basically does not exist (you need a local minimum in every single dimension at once). Not to mention that in this case it's not a continuous fitness landscape - you can make wild jumps in each evolutionary step, so the situation of "maximum that can't be climbed out of under given constraints" is even harder to come by.

Indeed. Sunlight alone can't pull a significant amount of water out of the atmosphere, and plants/bacteria need additional energy in the form of sugars to pull carbon out of CO2 in the air.

Where's all this energy coming from?

>plants/bacteria need additional energy in the form of sugars to pull carbon out of CO2 in the air.

Sorry perhaps this is not what you meant to write. For anyone who wants an unmangled understanding of photosynthesis please consult Wikipedia or other text of your choice.

Yes! I am pretty sure that I got confused ... either getting the Krebs Cycle the wrong way around or confused about where the ATP came from... Possibly the latter, this will teach me to comment about half remembering biology from over 25 years ago whilst still half asleep ..

However my original poorly explained thought stands there needs to be an extra component that will be consumed like ATP or H2O...

There is glucose in the compound, as per the article.

Lime-based mortar has been doing so since the Roman times.

Of course this is development is different, but it's still not scalable in any way. If your material isn't alive it won't last long, the catalysts always decompose or degenerate fast.

> The chloroplasts are not alive but catalyze the reaction of carbon dioxide to glucose.

That reaction also consumes water. So, would you need to regularly mist the material with a spray bottle to keep the self-healing going?

In places with rain, this problem can be solved with rain

I want to know where all the glucose comes from!

Carbon dioxide? Isn't the whole point of photosynthesis to turn CO₂ into glucose?

I think I got confused ... either getting the Krebs Cycle the wrong way around or confused about where the ATP came from... Possibly the latter, this will teach me to comment about half remembering biology from over 25 years ago... However my original poorly explained thought stands there needs to be an extra component that will be consumed like ATP or H2O...

Yes, water. The simple, high school biology version of photosynthesis is: 6CO₂ + 6H₂O + light -> C₆H₁₂O₆ + 6O₂. ATP is what plants get from burning that glucose.

Yes, but that's (your chemical reaction) a very simple explanation of photosynthesis.

The reactions in chloroplasts , according to Wikipedia at least, is much more complex. It seems that it's a multi-purpose process that eventually results in glucose.

I'm happily not a biologist.

They include it in the mix:

> The material the researchers used, a gel matrix composed of a polymer made from aminopropyl methacrylamide (APMA) and glucose, an enzyme called glucose oxidase, and the chloroplasts, becomes stronger as it incorporates the carbon.

Could you “clean the air” by creating many such breaks and having it pull co2 out of the air?

Technically yes, but practically no.

It'd be a very inefficient and slow way to "clean the air. The materials still need to be invested with whatever energy (e.g. glucose) is going to be consumed by the process, and once it finishes you're stuck with some hardened inert lumps which may not be cheaply recycle-able.

Pound of cure, ounce of prevention -- the cheapest and easiest way to clean the air is top stop putting schmutz in it.

That said, if you're really interested in using biotech to pull carbon out of the air, probably the best approach involves reusing existing plant or algae species. and simply harvesting them to bury in such a way that they won't be uncovered for a couple hundred million years.

After all, they're far more robust, feature-packed, and battle-tested than any grey-goo we can make for ourselves in the near future.

> probably the best approach involves reusing existing plant or algae species. and simply harvesting them to bury in such a way that they won't be uncovered for a couple hundred million years.

As a bonus, you're helping out a future civilization by seeding their oil reserves. Talk about paying it forward...

Maybe that's what happened last time.

As far as I’m aware, plants are fairly inefficient at absorbing carbon from the atmosphere.

It’s conceivable a process could be created that pulls carbon from the atmosphere more efficiently while not hsving to deal with all the other mess biological live entails.

It’s also possible you’re right, this isn’t possible, and biological life is the best we’ve got.

As a thought experiment, we release 40 billion tons of co2 per year. An average skyscraper weights around 250,000 tons. So that would be the equivalent of 160,000 skyscrapers worth of this stuff. Hong Kong has the most skyscrapers current at 317. So it would be the equivalent of building the skyscrapers for a city that is 500 x the size of Hong Kong every year.

Not that you'd have to build skyscrapers with the material, but just to put this idea in some sort of perspective.

Skyscrapers are mostly empty space inside. The Great Pyramid of Giza weighs about 6 million tons, so we’d be producing about 7000 of them annually. Maybe we could just plop them all in the ocean? ;)

I'd probably mess up the arithmetic, but I wonder how many skyscrapers or Great Pyramids could be packed in a volume of 1 cubic mile. That's how much oil we use per year.[0] (All sources combined are equivalent to about 3 cubic miles of oil.)

It would be nice to find a way to bump that up a couple orders of magnitude without actually pulling that much oil/equivalent out of the ground, since there literally isn't enough there.

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

Start with a Great Pyramid of Giza, or locally sourced substitute following the traditional recipe [1]:

  * 5.5 million tonnes of limestone
  * 8,000 tonnes of granite
  * 500,000 tonnes of mortar
For a simple approximation, we ignore ingredients that are not limestone.

mass of limestone in great pyramid of giza

  = 5.5 * 1e8 kg of limestone
Volume of limestone in one great pyramid of giza, assuming medium-high density limestone at 2500 kg / m^3 [2]

  = 5.5 * 1e8 kg / (2500 kg / m^3)
  = 2.2 * 1e5 m^3
allegedly there are 4.168e+9 m^3 cubic metres per cubic mile. That gives about 19,000 great pyramids of giza per cubic mile.

[1] https://en.wikipedia.org/wiki/Great_Pyramid_of_Giza#Material... [2] http://www.natural-stone.com/limestone.html

edit: when i try to estimate by geometry from the pyramid dimensions, instead of by density, i end up with about 2,000 great pyramids of giza, but that's without trying to understand what the volume of a pyramid actually is, because i am not clever enough to do that.

Intuitively, isn't the volume of a pyramid going to be 1/3 of that of a prism with the same width/length/height?

Pass 1: culture a huge amount of spinachs that pull co2 out of the air

Pass 2: distroy this plants releasing co2 again in the air to obtain chloroplasts from the upper half of the creature. Set free again the co2 saved in roots. (Alternatively pick only leaves from the spinach).

Pass 3: use this chloroplasts to recover a part of the co2 released in the pass 2

Pass 4: ... D'oh!

> In ongoing and future work, the chloroplast is being replaced by catalysts that are nonbiological in origin

The next question is how much CO2 will be released during the manufacturing process for these catalysts.


Excuse the drive-by one-liner. Hard to resist.

Yes! (From "The Expanse" novels, also a sci-fi tv series.)

I'd pay for it, if it was embedded in car paint.

> While there has been widespread effort to develop self-healing materials that could mimic this ability of biological organisms, the researchers say, these have all required an active outside input to function. Heating, UV light, mechanical stress, or chemical treatment were needed to activate the process. By contrast, these materials need nothing but ambient light, and they incorporate mass from carbon in the atmosphere, which is ubiquitous.

Mechanical stress, I wonder if such materials would serve well as coating atop an office floor to reduce the indoor co2. Every step that gets taken would activate the process. Probably won't make as much of a difference as a decent AC unit though.

Oh man, here comes the grey goo.

I say, bring on the grey goo! It's simply a distillation of life's ultimate purpose, so why not use a more efficient version?

Greetings, fellow human! I, too, am excited by the idea of an emergent material phenomena somewhere between oil spills and a small pox pandemic!

Appears to be a tree that keeps growing after you cut it into boards.

Wait, how long does it take to 'heal'? Didn't see that in the article, and it's pretty crucial with regards as to how useful this can be.

As long as it heals at least a little faster than it naturally weathers this would be amazing for all sorts of things. Imagine if you could just paint steel with a coating that's as durable as hot dip galvanizing.

...until the sugar fuel in the coating runs out.

That's why I chose galvanization as an example. The coating acts as an anode until it's consumed.

So, the self filling water bottles don't work because of the energy required to extract H2O out of the air is excessive (think how much electricity is required for your dehumidifier) ... Extracting carbon from the CO2 in the air is going to need a heap more, I would have thought.

I'm not a physicist though, would be glad to be proven wrong.

It does sound very much like a "solar freaking roadways" type effort though.

Plants extract carbon from CO2 all the time. This material is using photosynthesis so I would assume it works close to as well as it does in plants.

Indeed I think I got confused ... either getting the Krebs Cycle the wrong way around or confused about where the ATP came from... Possibly the latter, this will teach me to comment whilst half asleep and half remembering biology from over 25 years ago...

However my original poorly explained thought stands there needs to be an extra component that will be consumed like ATP or H2O...

The ultimate war in misted battlefields (trumpet sound):

Fancy polymer made of delicious sugar!!!...

... against lichens and bacteria from the badass planet earth!!!.

Guess who of both will release chemicals, distroy their opponent and feed on their guts after being trained for millions of years in extreme survival (colonizing lava fields and sun scorched areas)?

Anyone in the field that can say as to when this is actually feasible? It says that they have investigated production by the ton but went back to improving its properties. Are we talking 10 years? 20? 50? I just want a ballpark estimate.

If this can remove CO2 from the air, I wonder if it could do so quickly enough to make an "air scrubber" for a future spacecraft...

Yea, we will call it "Amber" :)

Who knew Dr Walter Bishop perused HackerNews.

The cynic in me expects to click this and find an article about trees.


The more I know about biology the less I enjoy (applied and commercial) science because .. well biology does much of it right now.

I remember listening to a AI researcher talk about how his quest to develop an advanced intelligence led him to realize he could do that by having a child.

Remember his name ?

I always thought that the limit of cyber/ai if eco-friendly survival, self-repair to an extent and reproduction was factored in would be homosapiens.exe

Sorry, I don't. I'm pretty sure I heard it on an NPR broadcast in early August of 2001, but that's as much detail as I can recall.

Already a lot. I'll try my luck with that :)

Actually I think it was in April. I was headed to a U2 concert in San Jose when I heard it, and it looks like that was in April. Depeche Mode was in August :)

tomorrow morning you'll have an epiphany about the name

I bought some houseplants a bit back and it's been fascinating to see how quickly they grow. The vast majority of that new mass literally comes from thin air.

Then think about the internals, the subtleties of cellular matrices. It's as beautiful as processor manufacturing, if not more, and right before your eyes all around.

I laugh yellow~ when people dream of robotics.. when I see an annoying mosquito, I look at how thin all this is and yet it lives, flies, perceive the world quite a bit ...

To an extent I think the future will just be the same old past except we'll now understand nature a bit more. I hope so.

Dragonflies is where its at. These guys supposedly have one of the best eye vision of all species. Now compare that thing with flying camera drones. Anything we can build is so much inferior to what a Dragonfly can do.

I’d doubt that. Compound eyes have inferior resolution compared to mammal/reptile/bird eyes.

E.g. a compound eye with the angular resolution of your current eyes would be about the size of your head.

Edit: nope, even bigger:

>To see with a resolution comparable to our simple eyes, humans would require very large compound eyes, around 11 metres (36 ft) in radius.


My favourite for this are South American tillandsia. They have no roots. They just sit on a tree branch and eat air.

Yeah, it's neat how roots mostly just bring in phosphates, nitrates, and water. Incidentally, carnivorous plants only get their phosphates and nitrates from whatever they trap. All of the actual carbon in all plants come from the air or from dissolved CO2 in the water.

There's a certain fetish for technology that blinds us to the obvious power of biological systems. We end up chasing pipe dreams of self-assembling materials while ignoring the already-existing self-assembling materials right in front of us.

There's a difference in knowing how to use a TV and knowing how to design and manufacture a TV.

Or a difference between Jesse Pinkman and Walter White.

I guess we don't need to stretch this joke too far.

It’s called a god complex? But the pragmatic reasoning is that what we build we can control more so than what nature has evolved. If for example, I can build a robot to pick up my trash can and walk it down to the street once a week and it’ll self heal all the wear and tear that is pretty nice.

God complex as the ignorance / greed spectrum.

It only works if you can sell your [bad re]creation to an audience.

I have no idea what you're talking about.

There are enormous areas of research built around adapting the already-existing self-assemblers to make new things.

Well, if you can find a tree that can be poured into a mold...

You should click and read the article then, because the new material uses chloroplasts (a plant cell organelle).

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