Abstract
Carnivorous plants have evolved leaves into unique functions to adapt infertile environments. Genus Nepenthes has pitcher for attracting and retaining the prey. Peristome, a rim that surrounded on the top of pitcher, is a trap activated in wet and moist conditions. Ridge-like hierarchical structure of peristome surface enhances the superhydrophilicity and results in anisotropic wetting. This research focused on the microstructure and wettability of peristome. Wetting efficiency of peristome was measured under 3 conditions (fresh, critical point dryer-treated and sucrose-coated) under controlled temperature and relative humidity to elucidate the wetting mechanism. In order to understand the effect of microstructure of peristome on the wetting properties, two kinds of polymer, PDMS and NOA 63, were used to mimic the surface of peristome via replication method. The replicas not only well preserve the original structure but exhibit nearly superhydrophobicity (contact angle ~140) and anisotropic wettability due to the parallel ridges on the surface. Surface modifications were further employed on the surface to adjust the surface properties. Spray coating and sol-gel methods were utilized to deposit smaller PDMS-TEOS cross-linked particles on replica and form hierarchical structures, exhibiting both superhydrophobicity and water-repellency. On the other hand, atmospheric pressure plasma was applied to generate hydroxyl groups on the surface, leading to temporarily hydrophilic surface. The hydrophobic recovery time of NOA 63 was longer than that of PDMS. Results indicate that the unique microstructure of peristome can be utilized in various processes and materials to synthesize novel bio-inspired materials with multifunctional surface properties.