The use of Experiment funds, the fabrication of transparent wood, and research directions

Detailed Objectives:

• Translational materials research

  • Optimize the protocol for attaining transparent wood (TW) that is translatable from the laboratory setting into the field of industry for scalable, creative commercial production.

  • Experiment with patterned TW designs that selectively depolymerizes lignin, initiates clear aromatic substitution, and infuses epoxy resin on the created design pattern whilst sustaining the natural wood on unpatterned regions.

  • Test different transparent, aromatic, and organic reagents (for lignin chromophore substitution) and adjust protocol procedures to suit scalable commercial production.

  • Identify adjustable variables (e.g. color gradation, wood thickness, end grains, wood species, vacuum pressing) that introduce new functionalities and versatilities in TW.

  • Collect SEM images at 100-150um, transmittance and absorbance data for resin-infused TW materials, and FTIR spectroscopy data to show preserved lignin content.

• Creative design projects

  • Introduce woodworking-based methods that facilitate design and introduce new multifunctionalities in product creation involving TW.

General Procedure:

Attain ash and balsa wood from Berea College Woodcraft Department. Prepare wood veneer samples by cutting a 0.5-2mm thin by 5cm^2 sample. Prepare 12-30% H2O2 and 10% NaOH solution and brush over the desired surface of the wood sample followed by artificial or sunlight UV-A illumination until samples are bleached (depolymerized chromophores). Wash the treated wood samples in ethanol or isopropyl alcohol to remove any remnant bleaching reagents and transfer the washed samples to toluene (variable aromatic reagent). Afterward, impregnate the wood samples with epoxy resin by vacuum infiltration. Lastly, store the epoxy-filled TW samples at room temperature and allow to cure. Repeat protocol with various wood species cut in the transverse and longitudinal direction to ensure versatility of the method amongst various hardwood species. Additionally, devise and test new craft-based functionalities that can be introduced to TW for sustainable, novel, commercial production in the craft industry.

Update & Present Results:

Since the arrival of research funding from Experiment members and crowdfunders (who we thank greatly for providing the opportunity), we have successfully acquired transparent wood (TW) materials for transverse ash wood and longitudinal balsa wood samples (Figure 1 A-C). Furthermore, we are presently testing the photocatalytic bleaching procedure amongst three hardwood species (Figure 2 A). The provided support allowed our research cohort to purchase AeroMarine epoxy resin #300 and Non-blushing Cycloaliphatic Hardener #21, which has the necessary refractive index for tailoring the optical functionalities in these hardwood species. Additionally, Experiment funding support has allowed the purchase of a 3-gallon vacuum pump and chamber necassry for chemical and resin wood infiltration to fabricate TW. Meanwhile, the Chemistry Department of the college continues to provide support in ordering and documenting chemical reagents, providing lab space, and allowing instrumentation use.

Moreover, the results we have attained suggest the feasibility in the project as it will continue through the month of May and the Fall 2023 term. Currently, we have shown that the transverse-cut ash wood has been depolymerized on the chromophore groups of lignin biopolymers and successfully substituted with a transparent aromatic reagent, toluene, to induce new transparent functionalities (Figure 1 A). Additionally, after resin mixing, we submerged the toluene-washed wood template in a silicon mold filled with epoxy and vacuum infiltrated the wood. The resulting material has provided preservable TW ash samples that have been epoxy-impregnated to engender transparency and enhanced structural durability whilst remaining entirely biodegradable (Figure 1 B). We have reproduced TW through several trials using longitudinal cut ash and balsa wood templates, also in larger sample sizes, to represent the scalability of TW fabrication between two crucial hardwood species in the woodcraft industry (Figure 1 C; longitudinal ash not shown here).

 

Figure 1. Production of transparent wood samples. A. Transversely cut ash wood samples. Natural ash wood enf grain (left) and lignin depolymerized, toluene-infiltrated ash wood samples with transparent functionality (right; length bar applies A-B). B. Epoxy-infused transparent ash wood samples. C. Ash wood (top) and balsa wood (bottom) transparent wood samples.

 

Figure 2. Photocatalytic depolymerization of lignin in different wood species. A. Natural and lignin Depolymerized ash, oak, and cherry wood samples. After UV-A illumination with bleaching reagents, ash wood became bleached whilst oak and cherry wood were partially bleached. B. Brief schematic of photocatalytic depolymerization method.

Further, we began the fabrication process of TW in other wood species critical for engineering and craft (Figure 2 A). Here, we bleached white oak and American cherry wood, which both have greater hardness and structural contents than white ash wood, for approximately 16 hrs. and only the ash wood became fully lignin depolymerized (Figure 2 A). We originally had a walnut wood sample (shown in the unedited image), but the template became increasingly brittle and fractured during bleaching. Additionally, we express the general procedure for wood bleaching in the schematic above (Figure 2 B). Inferably, we have discovered reaction timing is dependent on the structural and lignin content of wood samples, which we will seek to correlate between samples of variable lignin composition.

Lastly, we acknowledge that, since the commencement of the Spring 2023 term, fabricating TW optical functionalities for bleached ash wood and balsa wood templates has offered issues in lignin modification with toluene submersion and epoxy resin infiltration. This has caused a setback in the original milestone planning in research. Though, in assisting the research endeavor, the Woodcraft Department has offered silicon mats and molds, which has significantly reduced the outcome for failed resin infiltration trials. We also state that the college's SEM microscope is currently dysfunctional and is undergoing repair for the summer. We intend to pursue data acqusition in the fall and continue TW fabrication through the May period. Conclusively, the project team wants to thank the Experiment funders for backing and facilitating the research and the opportunity to fabricate TW materials.

Research Directions:

Presently, we intend to continue the fabrication of TW of various species, different dimensions, and using less hazardous aromatic or organic reagents for the feasible, commericial implementation of TW into the craft industry. We are also exploring modalities of pattern creation using fine printing of the bleaching reagent or laser engraving-assisted TW patterns.

Disbursement Summary:

With the funding provided, the research team has successfully purchased the HZUATOS 3-gallon vacuum pump and chamber, the 300/21 AeroMarine epoxy resin and Non-blushing Cycloaliphatic hardener, and the 3W 395nm UV-A lamps necessary for the production of TW materials. Furthermore, we have purchased dishes for containing the sample in reagent solution and the Professional VacuPress Pump for upscaling the project to commercial production. See images below.

 

Images: Materials purchased. AeroMarine resins and hardener (top left); sample dish and UV-A lamp (top right); Resin vacuum pump and chamber (bottom left); and the VacuPress pump (bottom right).