Viscoelastic effects in small-scale indentation of biological materials

Modern developments in instrumentation and analysis have vastly increased the popularity of instrumented indentation and nanoindentation techniques for mechanical characterisation of materials. However, these techniques have been developed primarily for materials exhibiting time-independent mechanical behaviour and therefore have had limited applicability in the mechanical analysis of time-dependent biological tissues. Following a brief introduction on elastic and elastic-plastic indentation, the current paper reviews the existing analytical machinery available for indentation analysis of viscoelastic materials (as developed in the context of polymeric materials). Recent works are reviewed in which the application of viscoelastic indentation techniques is extended to small-scale testing of biological tissues.