Engineering Tough Materials: Biomimetic Eggshell

This final report summarizes the work completed on the two year pilot project, which concluded 31 July 2016. The first section summarizes the two previous reports to place the current work in context. Two new research results sections are included here. The first concerns the use of a synthetic peptide, mimicking natural eggshell protein believed to be influential in biomineralization, to examine its effect on CaCO3 formation, including a polymer-induced liquid precursor (PILP) mineralization. The second examines the interesting role of the eggshell membrane in shell fracture, demonstrating that it is intimately mechanically connected to the shell long after shell formation and mineralization. The report concludes with a brief outlook, including next steps to pursue in the new cooperative research arrangement between ERDC and the University of Cambridge. Summary of Previous Reports Preliminary report of 30 January, 2015 The preliminary report had two parts. First, the literature on biomimetic calcite synthesis was reviewed, with an aim of establishing gold-standard techniques for making biomimetic eggshell in large quantities. The literature was found to be surprisingly uniform in that most controlled studies of calcite biomineralization have utilized a vapor diffusion technique, where calcium is in solution and carbon and oxygen atoms or ions are introduced as a gaseous phase. Although well controlled, this process is slow and produces only small quantities of material. As such, the evidence supports our continuing with solution-based calcite synthesis with a mind towards scale-up of material synthesis for eggshell-like material in large quantities. Second, the results of a series of preliminary experiments on this project were presented, comparing calcitic materials produced in our laboratory with natural eggshell. Spectroscopy was utilized to examine the mineralization of calcite and the presence of amorphous calcium carbonate in the calcite matrix. Thermal analysis was used to establish the presence of organic materials within calcium carbonate.