The COSY Division is pleased to invite you to the talk given by Dr Anika KAO (Marseille Université, France), entitled Exploring in vivo skin mechanics: A multi-faceted approach using 3D Digital Image Correlation, that will take place on Thursday April, 24th from 1:00 pm to 2:00 pm in the Maisin Auditorium (LEW).

Abstract: With broad implications across healthcare and technology, a deeper understanding of skin mechanics has potential to drive advancements in diagnostics, therapeutics, personalized medicine, and the development of bio-inspired materials. However, characterizing the complex mechanical behavior of human skin remains challenging due to its biological variability, non-homogeneous structure, anisotropic behavior, and non-linear stress-strain response. Current in vivo techniques, such as indentation, myotonometry, and ultrasound elastography, primarily assess static or quasi-static deformation, limiting their ability to capture the dynamic mechanics of everyday movement. To bridge this gap, this work develops and applies a non-invasive, high-resolution imaging approach using 3D Digital Image Correlation (3D-DIC) to quantify skin surface deformation across a range of biomechanical, clinical, and haptic applications. First, we optimize 3D-DIC for in vivo use, developing novel bio-safe speckling methods, adaptable camera configurations, and sophisticated analysis pipelines for characterizing skin surface deformation while minimizing interference with natural mechanics. Next, we applied the system to tactile perception studies on the finger pad, capturing fine-scale skin deformations in response to light-touch forces by von Frey monofilaments spanning perceptual thresholds. Results demonstrate that 3D-DIC offers sufficient range and resolution for tactile acuity studies, revealing distinct displacement and strain patterns that correlate with just noticeable percepts at absolute detection and discrimination thresholds. Third, we derived eleven strain-based biomarkers from 3D-DIC measurements of skin surface deformation during clinician-applied lateral stretch to quantify myofascial tissue mobility. These biomarkers captured distinct mobility patterns across pull direction and body side, reflecting anatomical asymmetries and correlating strongly with self-reported pain, supporting their potential as objective, clinically relevant tools. Finally, evaluating the sensitivity of the strain-based biomarkers to changes in mobility following STM intervention revealed increased tissue glide and reduced tissue resistance, consistent with prior literature, and a correlation between mobility and pain, with greater mobility improvements on the more painful side after treatment. These findings demonstrate that strain-based biomarkers at the skin surface can provide insight into soft tissue mobility, capturing both baseline asymmetries and intervention-induced changes while seamlessly integrating into clinical practice. This research integrates high-resolution optical imaging, psychophysical testing, and biomechanical principles to characterize dynamic skin deformation in vivo, providing a scalable, non-invasive tool for neuropathic assessment, rehabilitation, manual therapy research, and haptic technology development.