Dynamics of soft connective tissues and implications for synthetic biomaterials: interfacing the frequency and time domains

Abstract

Soft connective tissues found in the body have a mechanical role to support and transfer load, provide protection, to cells and organs across all physiological systems of the body. They typically function within dynamic loading environments. This review explores the characterisation of soft connective tissues under cyclic loading, with implications for replacement biomaterials. The aim is to identify how characterisation of material properties within a frequency-domain can be effectively exploited in a time-domain for engineering applications. Material properties, such as dynamic viscoelasticity, are reviewed for a range of natural soft connective tissues and selected synthetic replacement materials. A case-study for brain tissue is used to evidence how the frequency-time domain gap can be bridged. Synthetic biomaterials evaluated include long-term implantable polycarbon urethanes, as they are used widely in medical devices. A final case-study outlines how long-term implantable biomaterials, within a medical device, can be evaluated across time and frequency domains which can result in predictive tools for performance. In summary, soft connective tissues support and transfer loads, across all physiological systems of the body, their frequency-domain characterisation is beneficial as it enables clearer links to typical loading experienced within the body. Transferring the frequency-domain characterisation to the time-domain has engineering applications, with the potential for effective healthcare technologies including via numerical analysis of tissue mechanics such as finite element analysis.