Solar-assisted fabrication of large-scale, patternable transparent wood
cbc.ca
cbc.ca
> Here, we report a method to produce optically transparent wood by modifying the wood’s lignin structure using a solar-assisted chemical brushing approach. This method preserves most of the lignin to act as a binder, providing a robust wood scaffold for polymer infiltration while greatly reducing the chemical and energy consumption as well as processing time. The obtained transparent wood (~1 mm in thickness) demonstrates a high transmittance (>90%), high haze (>60%), and excellent light-guiding effect over visible wavelength. Furthermore, we can achieve diverse patterns directly on wood surfaces using this approach, which endows transparent wood with excellent patternability. Combining its efficient, patternable, and scalable production, this transparent wood is a promising candidate for applications in energy-efficient buildings.
This same group has previously described A Clear, Strong, and Thermally Insulated Transparent Wood for Energy Efficient Windows [3].
[1] https://en.wikipedia.org/wiki/Transparent_wood_composites
[2] https://advances.sciencemag.org/content/7/5/eabd7342
[3] https://onlinelibrary.wiley.com/doi/abs/10.1002/adfm.2019075...
“Bamboo fibre” bowls made with plastic for a recent trend: Not just not biodegradable as the name suggests, but also not recyclable.
Like “vegan leather” (made from processed crude oil), these terms only seem to take us away from the products that we are actually looking for when something says “natural”.
I think it would be fair to call this wood fiber reinforced epoxy sheets.
Same reason we use MDF rather than Medium-density fibreboard.
Honestly, the manufacturing process sounds much simpler than other “wood” I’ve seen that has much more engineering / chemicals involved.
Thankfully we have had similar naming laws around the “wood” you mention. They are not perfect, but they are enough if you know what you’re looking for.
Ultimately this is about material science and the various trade-offs inherent in each choice. Cedar-strip canoes have a highly valued aesthetic quality but "wood-strengthened epoxy" is an accurate description of the material; the epoxy, however, is not the distinguishing feature of cedar-strip, kevlar, nor fiberglass canoes.
Like all evolving innovations, "transparent wood" seems to be searching for its killer application and I don't expect the name used by researchers to continue if/when it finds product-market fit.
> Scientists develop transparent wood that is stronger and lighter than glass
That’s the article title, and it’s very easy to argue that they are looking to misappropriate the “wood = natural (and renewable) resource” properties. The current HN title from the paper even goes a step further by pairing it with “Solar-assisted fabrication“.
The normal bleaching process is quite energy intensive, so that is also a win.
No. If it's not 100% all natural it's green-washing.
Sure. But it's much more environmentally efficient in terms of water use, carbon emissions, etc if we can make sufficiently tasty and nutritious foods directly from plants rather than going through the inefficient animal step. Many people also have ethical objections to consuming animals.
As long as a significant portion of the material is from plants, rather than fossil origin, it's probably still an improvement.
Plastic used in long-life consumer goods is generally not recycled anyway (as opposed to the single-use PETE, HDPE, etc, plastics used in packaging).
At least a fully plastic cup made of a single plastic could theoretically be recycled easily. When you embed it now has to have specific processes to deal with that before being recycled, and those processes might have to be specific to that one product (or at worst: the process becomes “burn out all the impurities, throw the smoke in the air”)
Secondly that’s not the point.
Glass is a very energy consuming process, it’s heavy and a PITA to transport and it’s also a very good heat conductor which means for insulation you need to use multiple glass sheets with an air barrier.
This material is lighter, it’s a way to sequester carbon, it seems to be less energy intensive both to produce and transport and provides better insulation from the get go.
If this can be developed as a drop in replacement for window glass alone it can likely save a lot of energy both in the manufacturing and then in the heating of homes.
Even if it’s not biodegradable not everything needs to be, most glass isn’t recycled either, and it’s not like glass recycling is a particularly cheap process.
The glass from your glass recycling bin is usually just crushed and added as a filler to other materials not melted to make new glass.
The volume fraction of wood in the resulting product appears to be around 33%. So by volume it's two-thirds resin and one-third wood.
I was hoping the wood fraction would be slightly higher to justify calling it "transparent wood".
so they replaced the wood with epoxy, and called it wood. Like a car where you replace everything but the VIN so it keeps it's identity?
The article is scant on details so it may still be bunk, but I still think it sounds like an interesting application.
Not sure how they "infuse" it. That sounds like driving it deeper.
Years ago we had an opaque SLA prototype part. I came in the next day and it was mostly transparent. The M.E. told me they painted it clear...
NileRed did a video about preparing this from a different paper: https://www.youtube.com/watch?v=x1H-323d838
It seems that you just soak the thing in epoxy in a vacuum. The results were not great, though.
As you can see from the video it is basically impossible to scale this process to large pieces of wood. Discussions about replacing windows with this are pretty pointless I think.
If you read the new paper, one of the main properties of the new technique is that it does not affect the wood lignin, so that the final transparent wood has the same properties, almost, as the original wood. In this video you linked to, the techique involves completely removing the wood lignin (see 4:08). Clearly not the same thing.
Another huge difference: in this video, the wood is dropped into a boiling chemical solution for 12 hours. In the new paper, the solution is brushed onto the wood at room temperature, then the wood is left exposed to UV light (which can come from natural Sun light) for just one hour.
The video uses boiling, distilled water to wash the wood (for only around 15 minutes), then hydrogen peroxide (in an awkard attempt at removing the lignin left) after the chemmical treatment of the wood, while this paper just mentions using ethanol (5 hours immersion) to remove just the chemical solution from the previous step.
The video mentions that after all this, the paper it's based on says they still need to boil the wood into a 8% peroxide solution (the video author decides to use much less, though, at 3% due to "foaming" problems) until the wood turned white, after which they use ethanol to remove the chemicals. In the new paper, this step doesn't exist at all. The UV light is enough to achieve that and the wood had already been washed with ethanol.
Only the last step, using vacuum to infiltrate epoxy into the wood, seems to be similar between the two different papers (though the author of the video did not have a very good techique to do that... both papers are quite lean on details, so the author of the video can't be blamed here).
I mention all this because you and other people in this thread are choosing to dismiss this new paper based on a video about a completely different paper, using a totally different methodology, which shows that you're either trying to intentionally present misinformation to HN readers, or that you didn't bother to read the new paper at all and just assumed nothing new in it.
Please avoid such behaviour in public forums, the last thing we need is more disinformation and lack of depth in our dicussions.
I think nay saying needs to be seriously curtailed. It's far too effective for way too little actual content. This is a great example of a trend that's infecting and harming HN discussions.
We need more people to read up on a topic and have an earnest conversation around it. Gut reactions or memories from years gone by of old techniques aren't constructive and are actively destructive.
Nay-Sayers should see the way we used to make formic acid (literally distilling formicae, ants) vs now (massive petrochemical plants).
Bleaching can be done with gas phase or supercritical peroxide in giant autoclaves like those used to make treated lumber.
You scale up the end result, not each individual step.
some notable addition, H2O2 itself is a great bleaching agent but exposing it to UV creates the Ozone gas which is also used as bleaching agent for wood pulp in industries. so, the process accelerates in its own. this process could be further accelerated if H2O2 soaked/brushed wood is placed in transparent airtight container(glass aquarium with sealed lid) for sunlight UV exposure,this process increases the concentration ozone and can ultimately give better result.
Other notable thing is the thickness is 1mm only which reduces the required penetration depth of epoxy to only 0.5mm if applied from both side separately. In the video they used 3mm which is three times more thick. The 1mm thickness itself also a limitation for wide array of applications, further research to increase effectively increase the required thickness of wood will make it viable for bigger market.
btw,I really liked the newer process which uses the already well-known chemistry and give better results.
Ok, the process involves epoxying the wood... that would be enough to change sound properties of the wood.
Also the drastic change of 1 mm thick balsa wood from rigid to foillike around 00:27-28 in the "Movie S2" of the supplemental material is quite surprising: https://advances.sciencemag.org/content/suppl/2021/01/25/7.5...
So why are windows not made of plastic as we speak, very often?
Which raises the question of whether the same thing happens with this product, and if not, why not.
The trick to this is designing crushers which work mostly by grinding rocks against rocks, not rocks against metal. Wear is much reduced.
But, for extending beaches and most other uses you want textured sand that clumps together. As such people don’t mine river beds for large scale glassmaking as that sand is more valuable.
But what's the impact of cutting down trees + mining for some fraction of petroleum vs mining for glass? I would guess that it requires a rigorous and impartial analysis of the environmental impact.
Recycling could be difficult (once again, I don't have the domain knowledge), but that's only an issue if it needs replacing.
> However, while window glass may not be recycled easily, there are many options for keeping it out of the landfill. For example, it can be melted and re-manufactured into fiberglass, incorporated into asphalt, and even combined into reflective yellow and white road paints. Broken glass can be combined with concrete to create terrazzo flooring and countertops. Some companies even use old glass for landscaping materials and other decorative applications.
...but that's nowhere near a recycled window.
The issue with glass though isn't how it's handled once we're done with it. The issue with glass is energy loss. We lose a huge amount of energy to the windows in our home, and it might be worth it to make wooden window panels if it means that we end up consuming less energy HVACing our homes. Especially since house windows can be expected to last for decades, which amortizes their disposal cost nicely.
[1] https://www.buildup.eu/en/practices/publications/directive-2...
[1] https://www.energy.gov/energysaver/types-homes/energy-effici.... [2] http://www.engext.ksu.edu/buildingenvelope/windowsanddoors
And everyone just uses more AC. Which surely is not more expensive.
Oh and right, thats the reason Australia absolutely needs coal to burn.
The only remarkable thing is that they have succeeded to match so well the refractive index of the epoxy resin to that of cellulose and bleached lignin, so that the composite is a clear transparent material instead of being just diffuse translucent, like most composites.
This might make this composite a better choice than polycarbonate or acrylic glass in many applications.
They should have given a comparison between the properties of the new transparent material and those of polycarbonate, because that is their main target market, not glass. Anorganic glass cannot be replaced by polymers in many applications, due to requirements for chemical resistance or high temperature resistance.
It'd be great if it was cheaper. Even before the demand from the pandemic those were expensive.
I don't see this going anywhere unless that issue has been resolved for good. Does anyone know more about recycling epoxy?
--
Hmmm, some of the text under the photos in the article are extremely misleading:
Researchers demonstrated after brushing a coat of hydrogen
peroxide on the opaque wood material, and exposing it to
one hour of sunlight, it turns transparent.
I still think it is interesting and probably useful. But it starts off understating the actual effort involved.
> The obtained transparent wood (~1 mm in thickness)
And the wood was also from a balsa wood log, so this method is making something remarkably flimsy.
At least from what I saw in a previous paper on this idea, it sounds like it's fairly difficult to get the epoxy into a thicker wood sample.
If windows were made of something that could be splintered and more quietly pulled apart, I'm not sure it be as useful for the typical glass windows and doors we know.
Yes you could make it transparent, but cross grain was only slightly stronger than a stale cracker. He kept breaking the samples and gave up.
The problems could be in how long that "wood-glass" lasts. Will you see cracks soon? Will any insects start drilling your windows?
Yes, but that's why in certain areas you need to do termite inspections because the treated wood doesn't provide 100% protection. Also the wooden parts are normally protected by other materials to not be exposed to rain and rot - in this one the epoxy layer would likely do that, but still, it depends on good coverage/protection.
surely industry will find ways to reprocess recycled material to fit requirements??? or use more concrete or more rebar or something?
can the folks who mine river or marine sand be tasked to put desert sand back to replace what they mined?
And unlike corn-based plastics, the raw materials for glass aren't food.
https://www.theonion.com/geologists-we-may-be-slowly-running...
;)
Is this really wood? Can I hammer a nail into it and hang my coat without it breaking or even cracking?
(Like every article where a new material is "stronger than X")