Nanoindentation of biological tissues : review of the literature and design of a protocol for the characterization of the aortic wall

Biological tissues are characterized by an inhomogeneous, hierarchical structure determining their global mechanical behaviour. A multi-scale characterization is therefore crucial for a proper understanding of their properties. Nanoindentation is widely used to characterize industrial materials at the nanoscale, and has great potential for application on biological samples. However, such tissues exhibit viscoelastic properties that complicate the procedure. In addition, the mechanical behaviour of biological materials is strongly affected by the time, the conditions of the test and the scale at which the material is studied. For those reasons, nanoindentation has only limitedly been used for biological tissues and there are only a few well-established testing protocols. Hence, nanoindentation on biological material is still a young and challenging technique, that needs further improvements.This thesis presents the design of a procedure, involving both the preparation of the samples and the testing protocol, for the study of the mechanical properties of aortic tissues at nanoscale. Nanoindentation is used for this purpose. However, given the challenges linked to the application of the technique for the study of biological samples, a detailed review of the literature on the subject is first proposed. This review highlights the different existing approaches, their potential and limitations, and serves as a basis for the setup of the protocol developed in this thesis. The preparation of the samples and the consequences on their mechanical properties are first explored. Then, different nanoindentation protocols are compared to determine which one is the most appropriate for the characterization of the mechanical properties of the aorta.