Multiscale Mechanics of Eggshell and Shell Membrane

Eggshell is a target material for biomimicry: a biogenic material that is synthesized quickly under near-ambient conditions, and which has intriguing mechanical properties. Biomineralization in such natural systems utilizes organic molecules, both providing a surface to facilitate heterogeneous mineral nucleation and captured within the deposited mineral. Here, we examined the relationship between calcitic mineralized shell and the organic eggshell membrane. Elastic modulus and hardness of shell, as measured by nanoindentation in cross-section, exhibited approximately constant property values across three egg-laying species. Macro-scale fracture experiments demonstrated the structural importance of the fibrous eggshell membrane, with weak influence on egg fracture force but substantial effect on work of fracture. This effect was different for complete removal of the membrane versus chemical drying. The membrane thus represents a distinct target for improving egg mechanical properties independent of mineral quality.

Automated summary

Eggshell is a biogenic material synthesized quickly under near-ambient conditions, with intriguing mechanical properties. Research has shown that the elastic modulus and hardness of eggshell remain constant across different egg-laying species, indicating the importance of eggshell structure. The fibrous eggshell membrane has a significant effect on egg elasticity and fracture work, independent of mineral quality, making it a unique target for improving egg mechanical properties.