The project activities have been in three integrated areas: a) the science of transparent wood processing, b) structure-property relationships in transparent wood biocomposites and c) nanotechnologies for new devices based on transparent wood. The project team is cross-disciplinary with competence in wood science, polymer synthesis, nanostructured biocomposites and photonics. The contribution from physicists with optics and photonics expertise has been particularly important for team progress. This is not only through high productivity in terms of contributions to scientific publications, but also in development of experimental protocols, new ideas (wood for light wave-guiding and laser function) and focus on fundamental understanding of mechanisms for light scattering and absorption.
In processing science, the main concept is chemical pretreatment of wood veneer, followed by impregnation of polymer precursors and polymerisation. Several new methods have been developed and biobased polymer systems were developed. The optical transmittance of transparent wood has been investigated in great detail. This is critical in order to tailor these materials, and to come up with new material concepts. We keep increasing the understanding of how light travels through a complex material which is neither random nor highly organized in structure, but something inbetween. So far, we have not seen fundamental work in this direction in the literature. We published a combined theoretical and experimental approach to model light propagation mechanisms in scattering biocomposites. H Chen C Montanari R Shanker S Marcinkevicius LA Berglund, I Sychugov, Advanced Optical Materials 2022. DOI: 10.1002/adom.202102732.
The mechanical performance of transparent wood based on birch is exceptionally good. An important reason is in the new processing approach combined with removal of some wood components which do not contribute much to mechanical properties in polymer matrix biocomposites. Finally, many new devices have been investigated, including luminescent wood, a wood laser, electrochromic windows, transparent wood for heat storage using phase change materials, and solar cells. Plywood structures have been developed in order to control anisotropy of transparent wood laminates. In summary, the project is progressing well, and the team is functioning well with seamless integration between wood nanotechnology and photonics activities.
We have published 37 contributions in scientific journals, already with more than 1500 citations and many contributions are therefore obviously well-cited and in high-impact journals. This is particularly true if one considers the typical impact factors for publications in the area of forest products. In addition, 5 PhD-theses have resulted from the project. 2 of those PhD's are working in industry, 1 in a research institute and 2 are postdocs.
