Quasi-static responses of marine mussel plaques attached to deformable wet substrates under directional tensions

TL;DR

This study combines experimental imaging and finite element modeling to analyze how mussel plaques adhere to deformable wet substrates under directional tension, revealing the effects of pulling angle and substrate stiffness on failure modes.

Contribution

It introduces a novel microscopy and digital image correlation method to quantify substrate deformation and elucidates the mechanical interaction between mussel plaques and wet substrates.

Findings

Higher substrate stiffness increases load capacity.

Pulling angle influences failure mode transition.

Two failure modes identified: shear and normal traction-governed.

Abstract

Quantifying the response of marine mussel plaque attachment on wet surfaces remains a significant challenge to a mechanistic understanding of plaque adhesion. Here, we developed a customised microscopy system combined with two-dimensional (2D) in-situ digital image correlation (DIC) to quantify the in-plane deformation of a deformable substrate that interacts with a mussel plaque while under directional tension. By analysing the strain field in the substrate, we gained insight into how in-plane traction forces are transmitted from the mussel plaque to the underlying substrate. Finite element (FE) models were developed to assist the interpretation of the experimental measurement. Our study revealed a synergistic effect of pulling angle and substrate stiffness on plaque detachment, with mussel plaques anchoring to a 'stiff' substrate at a smaller pulling angle having mechanical advantages with higher load-bearing capacity and less plaque deformation. We identified two distinct failure modes, i.e., shear traction-governed failure (STGF) mode and normal traction-governed failure (NTGF). It was found that increasing the substrate stiffness or reducing the pulling angle resulted in a failure mode change from NTGF to STGF. Our findings offer new insights into the mechanistic understanding of plaque and substrate interaction, which provides a general plaque-inspired strategy for wet adhesion.