Transparent Wood Is a Surprisingly Versatile Material

By Nathaniel Scharping | May 16, 2016 3:38 pm
12TB-Wood-superJumbo

A block of wood before and after the two-step process to turn it transparent. (Credit: Liangbing Hu)

Wood makes for better walls than windows — most of the time.

Researchers from the University of Maryland devised a way to strip the colors and and chemicals from a block of wood to leave behind a clear, transparent material that’s stronger and more insulating than glass, and biodegrades better than plastic.

Only Two Steps Needed

The process of turning wood into windows is actually a pretty simple process. First, the researchers put blocks of wood in a boiling bath filled with water, sodium hydroxide and other chemicals for about two hours. This caused a polymer known as lignin to leach out of the cell walls in the wood. Lignin is one of the most common compounds in the plant world, and its chief function is making plant cells more rigid. Crucially for the researchers, lignin is also what gives wood its color — with the compound gone the wood turned white.

Then, the researchers soaked the wood with an epoxy, which both strengthened the wood and turned the wood clear. The secret lies in the natural architecture of the wood, combined with the refractive qualities of the epoxy.  Even though its color was gone, the underlying structures in the wood remained the same, including the tiny channels that trees use to transport nutrients. When filled with the epoxy, these channels turned into conduits for light, focusing it and allowing it to pass through. The end product looks more like a piece of plastic than something that once stood in a forest. They published their work in the journal Advanced Materials.

Wood Beats Glass

The transparent wood is stronger than glass and won’t shatter on impact. But wooden windows have a ways to go before they start appearing in homes.

Currently, the researchers can only treat wood chunks that are up to about four inches to a side. In addition, they are currently limited to about a centimeter in thickness, although they have made clear wood that is as thin as a sheet of paper as well. A separate team of Swedish researchers also recently managed to create transparent wood with a similar method, although their wood was not as thick, and did not let as much light through.

As of right now, the University of Maryland researchers say that their wood achieves a 90 percent transmittance rate for light.

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  • http://www.mazepath.com/uncleal/qz4.htm Uncle Al

    pretty simple process” “boiling bath filled with water, sodium hydroxide and other chemicals” Papermaking; don’t use a glass container – it dissolves.. “soaked the wood with an epoxy” Vacuum impregnate or air bubbles eat you. Did they dehydrate it first? Did they lyophilize the wood to keep it porous? “the end product looks more like a piece of plastic” What weight percent is the epoxy, that being plastic? You can do it with compressed white chicken feather barbs, too, and no lignin. So? Start by growing trees with ester lignins that trivially saponify and wash out, doi:10.1038/nature.2014.14992

    doi: 10.1007/s10924-007-0054-7 “the density [of] chicken feathers is about 0.8 g/cm^3 compared to about 1.5 g/cm^3 for cellulose fibers
    and about 1.3 g/cm^3 for wool

    Bisphenol-A diglycidyl ether epoxy resins cleave in sunlight at both aromatic ether linkages. Other epoxy resins will drain your wallet. Isocyanate resins also have sunlight issues re Gorilla Glue turning yellow. “Wood Beats Glass” Lizard eats Spock.

    • Ryan Cornell

      Ok. You’re smart. We all get it.

      • http://www.mazepath.com/uncleal/qz4.htm Uncle Al

        “Best efforts will not substitute for knowledge,” W. Edwards Deming. Things do not work well because they succeed. Things work well because they cannot fail. The first is Quality Control, and futile. The second is Quality Assurance, and substantive.

    • ThumbBeard

      Disqus résumé posted

    • Kevin Brock

      Density does not give linear structure to the molecules like in a block of wood. Chicken feathers or Wool will NEVER be as rigid and structurally integrated as wood.

      • http://www.mazepath.com/uncleal/qz4.htm Uncle Al

        The Trabant and Duroplast; carbon fiber fabric fill. For transparency, fiberglass; Plexiglas T high impact acrylic. The transparent wood hawkers should be boasting about noise attenuation.

    • Monkay Mune

      you’re hired!

    • waynyatta

      You took the words right out of my mouth.

  • mike hamblett

    Mm, sodium hydroxide, other chemicals and epoxy – wouldn’t want the factory near my house.

    • Holly Galligan

      and I’m over here like, hmmm… are the DIY instructions on Pinterest yet?

    • Dalton Sheldrake

      Sodium Hydroxide or Caustic Soda is the principle component of soap making. Nasty stuff but harmless if handled correctly compared to many of the compounds used in industry

  • John C

    Interesting

  • Bert Van Der Hulst

    The 2 pieces shown in the picture are not the same piece of material,the piece of wood has sharp corners and the piece that is transparent has rounded corners.

    • Paul Beverage

      Your observation does not mean they are not the same piece of wood. It only means there is a difference in the corners, which is not necessarily indicative of anything other than that fact.

    • Mark

      It’s called sanding you dip

    • Tommy D

      Not really. The thin section of wood is probably sitting in/on a glass slide with rounded edges. See the crystal clear border around the wood without lignin?

  • FortSteve

    Can we apply this same process to the Obama administration?

    • NuriaRodriguez

      Let’s go back a few years and apply it to the Bush Administration too.

      • Desiato

        A 2-fer!

      • Timea

        and the Clintons before them…

  • Eric

    Transparent wood? But is it stronger than transparent aluminum?

    • Chris Gray Hollomon

      the only comment needed, thank you..

  • Jim Demestihas

    so…..we either dump plastic in the oceans or cut own all he forests? not a good trade off……

    • Christopher Aaron McMahon

      difference being: Trees grow back, in MUCH shorter periods of time than plastic decomposes (if it ever does.)

  • http://www.rangate.com Rangate

    I wonder what how much conductivity change with newly introduced boiling solutions and eproxy. And when it burns, what gas is released? Inquiring mind wants to know… Chris

  • FrothFrenzy

    It’s hard to believe that a block of epoxy-infused wood will degrade faster than a chunk of plastic. Uncle Al, prove me wrong!

    • http://www.mazepath.com/uncleal/qz4.htm Uncle Al

      Moisture infiltration along the cellulose while solar UV cleaves both bisphenol-Al diglycidyl ethers’ AR-O-CH2- bonds. The Carboniferous Period’s end curiously coincided with fungi and bacteria learning how to eat cellulose – no more coal formation.

      If I want a superior fiberglass-epoxy composite, I cap the glass surface with an epoxy reactive silane from Gelest. Derivatizing cellulose in kind is not as simple.

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