Research ArticleMATERIALS SCIENCE

Solar-assisted fabrication of large-scale, patternable transparent wood

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Science Advances  27 Jan 2021:
Vol. 7, no. 5, eabd7342
DOI: 10.1126/sciadv.abd7342
  • Fig. 1 Schematic illustration of fabricating transparent wood and demonstration of its patterning.

    (A) Schematic illustration of this simple yet effective, eco-friendly, scalable, and low-cost method of fabricating transparent wood. Lignin not only endows natural wood with a brownish color but also serves as a binder for cellulose and hemicellulose. After chemical brushing and solar illumination, the lignin chromophore and hemicellulose are removed and the natural wood becomes colorless, but the modified lignin remains and can still effectively bind and wrap around the cellulose microfibrils to maintain the material’s mechanical properties. Then, epoxy can be easily infiltrated into the loosely packed lignin-modified wood microchannels to prepare the final transparent wood. (B) A digital image of a large-scale sheet of transparent wood (400 mm by 110 mm by 1 mm) along the longitudinal direction (i.e., the fiber direction). (C) A digital image of the transparent wood along the transverse direction (i.e., perpendicular to the fiber direction) patterned with a “tree leaf” shape. Photo credit: Qinqin Xia, University of Maryland, College Park.

  • Fig. 2 Structural and compositional characterization of the transparent wood.

    (A) The FTIR spectra and (B) the preserved lignin content of the natural wood, lignin-modified wood, and transparent wood. (C) A digital image showing the meter-scale fabrication of lignin-modified wood based on our method. Scanning electron microscopy (SEM) images of the transverse direction of (D) natural wood, (E) lignin-modified wood, and (F) transparent wood. The insets in the magnified SEM images show a detailed view of the micropores in the samples. SEM images of the longitudinal direction of (G) natural wood, (H) lignin-modified wood, and (I) transparent wood. The thickness of samples is 1 mm. Photo credit: Qinqin Xia, University of Maryland, College Park.

  • Fig. 3 The optical and mechanical properties of the natural wood and transparent wood.

    Digital images of the transparent wood along the (A) longitudinal direction (L; 400 mm by 110 mm by 1 mm) and (B) transverse direction (T; 70 mm by 30 mm by 1.5 mm). (C) The transmittance and (D) absorption of the natural wood and transparent wood (the volume fraction of lignin-modified wood scaffold: L, ~30%; T, ~33.2%). (E) Guided light propagation by the transparent wood. Photo images of the scattered laser light spot of the L- and T-transparent wood materials. (F) The tensile strength and (G) toughness of the natural wood and transparent wood. Photo credit: Qinqin Xia, University of Maryland, College Park.

  • Fig. 4 The fabrication process of the patternable transparent wood.

    (A) Schematic and (B) experiments demonstrating the fabrication process of the patterned transparent wood. First, H2O2 ink is printed on the wood surface using a brush, and these areas turn white after UV illumination. After the infiltration of epoxy, transparent wood with different patterns can be obtained, with various patterns made from natural wood along the longitudinal and transverse directions. The transparent wood patterned with (C) the number 4 and (D) letter A. (E) Circle and diamond and (F) yin-yang patterned transparent wood samples. Photo credit: Qinqin Xia, University of Maryland, College Park.

  • Fig. 5 Solar-assisted large-scale fabrication of transparent wood.

    (A) Schematic showing the potential large-scale fabrication of transparent wood based on the rotary wood cutting method and the solar-assisted chemical brushing process. (B) The outdoor fabrication of lignin-modified wood with a length of 1 m [9 August 2019 (the summer months) at 13:00 p.m. (solar noon), the Global Solar UV Index (UVI): 7 to 8]. (C) Digital photo of a piece of large transparent wood (400 mm by 110 mm by 1 mm). (D) The energy consumption, chemical cost, and waste emission for the solar-assisted chemical brushing process and NaClO2 solution–based delignification process. (E) A radar plot showing a comparison of the fabrication process for transparent wood. Photo credit: Qinqin Xia, University of Maryland, College Park.

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