Fig. 5.
Higher length scales of structure also improve adhesion performance. (A) Radial distribution of threads having a distal to proximal stiffness gradient. The stiff portion is in blue and the compliant portion is in orange. The compliant portion is typically concealed within the valves. (B) The spatulate geometry of a byssal thread and plaque [dashed line shows orientation of section for scanning electron microscopy (SEM) shown in C]. (C) The trabecular (spongy) structure of a plaque in SEM section. (D–F) The fracture mechanics of individual whole plaques in tension. (D) Schematic diagram of a plaque cross-section during tension. (E) Tensile force–deformation plot of a single plaque. (F) Photographic side (top) and underside (bottom) views of deformation in a plaque at point marked by asterisk in E are shown. Scale bars: 1 mm. Red circle indicates locus of plaque separation from the surface as sketched in D. The fracture energy Gc is derived from the force Fc by Fc/b=Gc/(1−cosθ), where b and θ denote width and pull angle, respectively. Adapted from Desmond et al., 2015.