Parthenocissus tricuspidata tendril: A mechanically robust structural design with multiple functions

Abstract

Through an array of spatially distributed tendril pads, Parthenocissus tricuspidata adheres itself firmly to the surfaces of targets such as trees and walls. The tendril pads, which form unique and intriguing layouts, play a critical role in supporting plant organs. However, the relationship between their geometric forms and mechanical properties remains inadequately understood. In this paper, we combine experimental measurement, theoretical analysis, and numerical simulation to decipher the morphomechanics of P. tricuspidata tendrils. The structural geometry and load-bearing capability of the tendrils were measured. A structural mechanics model, supported by finite element simulations, is proposed to analyze the properties of different tendril layouts. The results show that the gradually narrowing distribution of the pads and the zigzag pattern of the main axis synergistically make the tendrils a comprehensively excellent mechanical design. The tendrils can simultaneously achieve superb mechanical robustness, outstanding load-bearing capability, and high efficiency of material usage. We develop an optimization method, and find that the optimized tendril layout is similar to the real one. It is also revealed that the real pad distribution renders a flaw-insensitive design. As their branchlets or pads are partly broken, the tendrils can still effectively accommodate external forces in different directions, and their structural stiffnesses do not change significantly. This work not only deepens our understanding of the structure–property–function interrelations of P. tricuspidata tendrils, but also provides inspirations for the design of, e.g., high-performance suspended cables.