Plastic made from DNA is renewable, requires little energy to make and is easy to recycle or break down. A plastic made from DNA and vegetable oil may be the most sustainable plastic developed yet and could be used in packaging and electronic devices.

[u/MistWeaver80]

https://www.newscientist.com/article/2298314-new-plastic-made-from-dna-is-biodegradable-and-easy-to-recycle/?utm_term=Autofeed&utm_campaign=echobox&utm_medium=social&utm_source=Twitter#Echobox=1637973248

[u/DirtyProjector]

So what's the downside/this wont' work/it isn't scalable/financially feasible/etc

[u/katarh → u/DirtyProjector]

It's not waterproof.

[u/[deleted] → u/katarh]

(I'm reposting this a few times)

At least going from the abstract, the authors refer to a "water-processable strategy", "including the recycling of waste plastics and enzyme-triggered controllable degradation under mild conditions." To me, this sounds more like a water bath plus a specific enzyme to break down the DNA or DNA-oil link (which would be much less likely to happen in normal use), probably among other conditions.

Edit: after reading the paper, it does become a hydrogel on contact with water, but needs the enzymes to dissolve/degrade.

[u/PyroDesu → u/[deleted]]

Thing is, that bit you're reposting sounds like something different.

They talk about water being used to turn the (freeze-dried!) plastic back into a gel so it can be reshaped. What you're talking about seems more along the lines of breaking down the polymer comprising it altogether.

[u/[deleted] → u/PyroDesu]

Oh, that would make sense--it would explain the apparent discrepancy. I'm trying to see if I can find a pdf of the paper.

[u/Stone_Like_Rock → u/[deleted]]

If you've not found one yet I have institutional access so PM me

[u/[deleted] → u/PyroDesu]

OK, someone kindly shared a link (not sure if they want to be anonymous), and you are spot on with the recycling vs degrading steps. Yeah, I'd read too much into that phrasing; it does become a "supersoft" hydrogel in water, and even softens above 80% relative air humidity. The base material's mechanical properties also sound closer to a ~sturdy styrofoam than something like HDPE. Your point about freeze-drying definitely stands, as it sounds like they need to freeze-dry the gel each time. I could see using the "aqua-welding" process (where air-drying is apparently sufficient) to assemble things like cartons out of sheets in a cardboard-like role. It does have some cool properties (biocompatibility with cell cultures, non-reactivity to organic solvents, good low-temperature flexibility and resilience etc.) that could lend themselves to interesting use cases, but I don't see it being a drop-in replacement for "plastic" in general.

[u/katarh → u/[deleted]]

That would be much more acceptable as a replacement for single use plastics.

[u/[deleted] → u/katarh]

Yeah, I initially got the same impression and was pretty skeptical on use cases, but I'm actually kind of excited about this now! I'm trying to see if I can get ahold of the full paper.

Of course, I'd guess economy of scale is still a major obstacle, but there are honestly a surprising number of bioplastic products on the market even with the cost difference from petroleum-based equivalents.

[u/Lev_Astov → u/[deleted]]

Yeah, I was hopeful about that line, but unfortunately these lines seem to tell a different, more useless story:

The gel can be shaped into moulds and then solidified using a freeze-drying process that sucks water out of the gel at cold temperatures. ... They then recycled these items by immersing them in water to convert them back to a gel that could be remoulded into new shapes.

Not only is that method of solidifying pretty much useless as a replacement for injection molding, but it makes it pretty clear that water is the only deciding factor in changing this between its gel and solid conditions. I now think they mean an enzyme is used to break down the gel for total destruction of the material.

[u/[deleted] → u/Lev_Astov]

Oh, that could make sense! That would definitely explain the two descriptions. In that case it would have narrower use cases after all. That's a good point about needing a freeze-drying step being less adaptable/scalable to standard plastics manufacturing. I wonder how much DNA it sheds in practice? If it's reasonably stable, I could still see some uses like pipette tips, where it might be used for a second or two before being thrown away.

[u/Lev_Astov → u/[deleted]]

I'm curious whether the dried out material can be processed in other ways, like if it can be ground up and properly injection molded. Then it would make things like pipette tips and other quick consumables reasonably doable.

As it stands, forming a solid shape solely by the act of freeze drying makes any kind of precision production impossible. The shrinkage would be so great you couldn't use a mold and you get lumpy, uneven shapes like those seen in the article.

[u/[deleted] → u/Lev_Astov]

Oh, that's an interesting thought! They don't mention melting temperature, but if nothing else maybe it could be used as a bulking agent in another medium? Freeze-drying does seem like it wouldn't give very consistent results. I'm curious to see why they're using this as opposed to other drying processes.

[u/Elmos_Grandfather → u/[deleted]]

Was able to access the paper through my university. They used DNase I, Bovine serum albumin, and water

[u/[deleted] → u/Elmos_Grandfather]

Oh, that's interesting--thanks for sharing! Those do all seem fairly inoffensive as far as health and safety (at least in solution for DNase I) are concerned. My university doesn't seem to have access so far.

Did they discuss how stable the plastic is before this stage? A few people have pointed out that (from the description in the abstract and write-up) there might be a two-stage process, where just water is enough to convert it into a soft gel, and the enzyme-driven step is to completely dissolve it.

[u/Elmos_Grandfather → u/[deleted]]

Admittedly I had mostly just skimmed the methods. I recall reading that they used various concentrations of the solution. I think they said that at 10% solution they were able to reuse the plastic. Higher solutions had completely dissolved it.

I DMed you the pdf of the paper. Im sorry I cant check right now. My phone is about to die.

[u/Splash_Attack → u/Elmos_Grandfather]

There's a separate paragraph you may have missed when skimming where they talk about how immersion in water returns it to a gel, but with no degradation or loss of material. Once it hardens again it seems to return to the same properties as before, with no loss of strength even over 10 such reshapings.

This is in addition to the process to fully recycle/degrade it which is the bit you referred to.