Hierarchical Structure and Multifunctional Surface Properties of Carnivorous Pitcher Plants Nepenthes

摘要

Carnivorous pitcher plants of the genus Nepenthes have evolved specialized leaves fulfilling the multi-functions of attracting, capturing, retaining and digesting the prey, mostly arthropods. Different capturing mechanisms have been proposed and discussed in previous works. The most important capture mechanism is the unique super-hydrophilic surface properties of the peristome. The combination of a hierarchical surface structure and nectar secretions results in an exceptional water-lubricated trapping system. Anisotropic and unidirectional wettability is attributed to the ridge-like surface and epidermal folding. The three-dimensional plate-like wax crystals in the hydrophobic waxy zone can further prevent the prey from escaping. The captured prey are then digested in the hydrophilic digestive zone. The hybrid species Nepenthes x Miranda was investigated in this study. The surface morphology and hierarchical microstructure were characterized by scanning electron microscope. Contact angle measurement and wetting efficiency tests were performed to determine the wettability of the peristome under fresh, nectar-free and sucrose-coated conditions with controlled temperature and humidity. The results showed that sucrose-coated peristome surfaces possess the best wetting efficiency. The structure-property-function relationship and the capturing mechanism of Nepenthes were elucidated, which could further lead to the design and synthesis of novel bio-inspired surfaces and potential applications.