In-vivo dynamic mechanical analysis of human skin: A standardized protocol using SkinMech-DMA

• First in-vivo DMA protocol for skin: We introduce SkinMech-DMA , the first device and standardized protocol enabling continuous, cyclic dynamic mechanical analysis of living human skin . • Novel methodological framework: A newly defined apparent modulus , validated by finite element analysis, provides a practical and reproducible parameter for in-vivo tissue characterization. • Validated accuracy and sensitivity: Device performance was rigorously benchmarked against a universal tensile tester using silicone elastomer surrogates, confirming high stability and precision. • Reveals fundamental skin mechanics: In-vivo measurements demonstrate frequency-dependent softening, anisotropy, nonlinearity, and viscoelastic energy dissipation across facial and hand sites. • Significance for biomaterials and clinics: This platform establishes the foundation for a standardized biomechanical database of human skin , bridging biomaterials design, clinical dermatology, and digital-twin modeling. Accurate characterization of skin mechanics is essential for understanding aging, pathology, and the design of biomimetic materials. However, in-vivo methods capable of quantifying the dynamic viscoelastic properties of skin remain limited. We present a Dynamic Mechanical Analysis (DMA) approach using a voice-coil motor-driven system that applies cyclic tensile loading to living skin. Crucially, we introduce an apparent modulus definition validated by Finite Element Analysis (FEA), enabling quantitative, site-specific, and frequency-dependent characterization. Feasibility was confirmed on silicone elastomers, where results matched a universal tensile tester, demonstrating accuracy and sensitivity. In-vivo measurements on facial and dorsal hand skin revealed key dynamic material behaviors, including frequency-dependent softening, anisotropy, nonlinearity, and viscoelastic energy dissipation. This methodology for standardized assessment of human skin mechanics can bridge biomaterials research and living tissue analysis and provide a foundation for future clinical and translational applications.