Mechanistic Insights into Wettability Evolution in Palm Leaf Manuscripts: From Natural Architecture to Aged Surfaces

Wettability, a fundamental issue in surface science, plays a pivotal role in the degradation behavior and conservation effectiveness of cultural heritages, especially for organic ones. In this research, we present a comprehensive investigation into the wettability evolution of palm leaf manuscripts, a special yet valuable organic artifact retaining most of its natural features. This study includes the entire transformation from fresh leaves to traditionally treated manuscripts and, subsequently, to artificially aged samples, providing a unique model to decode how surface microstructure and chemical composition collectively govern wettability behavior. Wettability change was quantified by contact angle and surface energy, revealing a clear shift from hydrophobic (fresh sample) to moderately hydrophilic (treated sample) and finally to highly hydrophilic (aged sample) states. To explain this variation, we used structural characterizations (LCSM, SEM) with surface chemical analysis (XPS, PY-GC/MS, FTIR, ¹³C NMR, and EDS). These methods together reveal changes in surface roughness, topographic integrity, chemical composition, and functional groups across different states of the leaves. The results demonstrate that the wettability evolution is strongly influenced by the native surface architecture. The removal of nonpolar lipids and waxes is the key trigger for the hydrophobic-to-hydrophilic shift. Besides, the exposure and oxidation of the inner polysaccharides amplify surface polarity and water affinity. This trend was further supported by the contact angle and spreading behavior of ink, revealing enhanced ink affinity on aged surfaces. These findings deepen our understanding of surface evolution in palm leaf manuscripts and highlight the practical significance of wettability for their writing and conservation.