Biological Mechanical Properties Study of Oyster Shell

As material science evolves, researchers have turned to biological materials for inspiration. The strong mechanical properties and unique structures of biological materials have been heavily researched in an attempt to replicate them. Desirable material properties, such as hardness and flexibility, can be traced to how micro/nano structures are naturally formed. To demonstrate a quantifiable way of collecting data on material properties on biological material, the NANOVEA Mechanical Tester’s Micro module is used to perform indentation and coefficient of friction (COF) tests on different microstructures of an oyster shell.

The NANOVEA Mechanical Tester’s Micro Module is ideal for collecting local material properties on the surface of the sample. Insights on the relationships between microstructure and mechanical performance can be formed from the material properties each microstructure possesses. This can provide information on the multifunctionality of the biological material and its benefits for the organism’s survival in nature. These insights can also be used to help synthetically replicate biological materials.

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The following indentation parameters were used:

It should be noted that the layers beneath the microstructure can influence the hardness and Young’s modulus. As a result, the values observed should not be taken as an absolute value, but comparative amongst the other microstructures. From the data gathered, Microstructure #2 shows a higher hardness than microstructure #1.

While the standard deviation for hardness and Young’s modulus is large for microstructure #2, the average values between the two microstructures are distinctly different from each other.

The NANOVEA Mechanical Tester’s Micro Module displays its ability to obtain hardness and Young’s modulus on two different microstructures of an oyster shell. The two microstructures have distinct hardness and Young’s modulus values, giving insight into the strength from the arrangement or composition of the microstructures themselves.

While only indentation tests were conducted in this study, these additional functionalities in the NANOVEA Mechanical Tester may prove useful for other biological materials: viscoelastic creep, Martens hardness, ultimate yield strength, multi-cycle test, and fracture toughness. High sensitivity, low load tests can also be conducted with the NANOVEA Mechanical Tester’s Nano Module.

A coefficient of friction test was conducted by running a linear constant load scratch test. When targeting COF properties, minimal damage and penetration to the sample is desired to minimize influence beyond the surface. As a result, a low load of 300mN and an indenter that will give a large contact area was used.

The results show microstructure #1 has a larger average COF than microstructure #2. Standard deviation for each microstructure is low, showing high consistency for the data collected.

The study on the COF of different microstructures yielded values of 0.2044 ± 0.0141 and 0.1451 ± 0.0042 for microstructure #1 and #2 respectively. From the tests conducted, the NANOVEA Mechanical Tester’s Micro Module has successfully characterized the COF on the two microstructures of the oyster shell.

In this study, the COF was gathered under normal, dry conditions. The NANOVEA Mechanical Tester can also include other add-ons to conduct testing under different environmental conditions, including lubrication, humidity, and temperature. These testing conditions can also be applied to indentation testing.