A comprehensive understanding of tissue mechanics at the microscale is critical for advancing personalised therapies, controlled drug release, and tissue engineering. Characterising the mechanical properties of complex, soft biological materials-particularly multilayered and anisotropic organs such as the skin and eye-remains a significant challenge due to their variable water content and scale-dependent behaviour. Traditional continuum models and linear material responses often fail to capture the dynamic and nonlinear nature of these tissues under physiologically relevant conditions. This review provides a strategic overview of state-of-the-art techniques for probing the mechanical properties of soft biological tissues, with a focus on skin and ocular systems. Our focus on the skin and eye reflects their favorable barrier properties for topical drug delivery. We examine visualisation methods including optical imaging, interferometry, digital image correlation, optical coherence microscopy, and acoustic imaging. In parallel, we assess actuation mechanisms such as indentation, cavitation rheology, and flow elastography, highlighting their suitability for in vivo applications. Each technique is benchmarked against key operational parameters-spatial resolution, acquisition rate, invasiveness, and strain rate-relevant to drug delivery and therapeutic engineering. By mapping the landscape of mechanical characterisation tools, this work offers a valuable resource for researchers in biomedical engineering and beyond, including fields such as physics and chemistry, where accurate dynamic analysis of soft complex materials is essential.
Villaescusa et al. (Thu,) studied this question.