Open AccessThe Structural and Mechanical Basis for Passive‐Hydraulic Pine Cone Actuation
Author(s) -
Eger Carmen J.,
Horstmann Martin,
Poppinga Simon,
Sachse Renate,
Thierer Rebecca,
Nestle Nikolaus,
Bruchmann Bernd,
Speck Thomas,
Bischoff Manfred,
Rühe Jürgen
Publication year - 2022
Publication title -
advanced science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.388
H-Index - 100
ISSN - 2198-3844
DOI - 10.1002/advs.202200458
Subject(s) - materials science , biological system , conifer cone , wetting , displacement (psychology) , finite element method , cone (formal languages) , composite material , biomedical engineering , mechanics , computer science , physics , thermodynamics , psychology , ecology , psychotherapist , biology , medicine , algorithm
The opening and closing of pine cones is based on the hygroscopic behavior of the individual seed scales around the cone axis, which bend passively in response to changes in environmental humidity. Although prior studies suggest a bilayer architecture consisting of lower actuating (swellable) sclereid and upper restrictive (non‐ or lesser swellable) sclerenchymatous fiber tissue layers to be the structural basis of this behavior, the exact mechanism of how humidity changes are translated into global movement are still unclear. Here, the mechanical and hydraulic properties of each structural component of the scale are investigated to get a holistic picture of their functional interplay. Measurements of the wetting behavior, water uptake, and mechanical measurements are used to analyze the influence of hydration on the different tissues of the cone scales. Furthermore, their dimensional changes during actuation are measured by comparative micro‐computed tomography (µ‐CT) investigations of dry and wet scales, which are corroborated and extended by 3D‐digital image correlation‐based displacement and strain analyses, biomechanical testing of actuation force, and finite element simulations. Altogether, a model allowing a detailed mechanistic understanding of pine cone actuation is developed, which is a prime concept generator for the development of biomimetic hygromorphic systems.