Laser-drilled functional wood materials show improved dimensional stability upon humidity changes – a neutron imaging analysis

Abstract

Wood and wood-based composites are increasingly studied because of their potential to regulate indoor humidity through moisture exchange with the air. Understanding their dimensional stability under fluctuating moisture conditions is essential for uncovering the underlying mechanisms and their practical use. This study employed neutron imaging to elucidate the moisture dynamics within wood materials under varying relative humidity conditions. High-resolution and in situ golden ratio tomography provided insights into moisture distribution and dimensional changes within the wood. Affine and non-affine registration techniques identified both the global and local deformations, highlighting dimensional instability in native wood and its improvement through laser drilling. Structural modification by laser drilling processes is effective in improving the moisture transport speed in wood and limiting dimensional changes. Moreover, the laser-drilled wood provides a highly feasible scaffold for further chemical modifications. Coating the cell lumina surface of laser-drilled wood with MOFs results in remarkably high moisture sorption capacity and improved dimensional stability compared to native wood and laser-drilled wood. The MOF layer acts as a barrier during water adsorption and as a reservoir during desorption. This study presents a promising strategy for the development of high-performance wood materials that leverage wood's inherent benefits while overcoming some current limitations.