A Dynamic Mechanical Analysis Device for In Vivo Material Characterization of Plantar Soft Tissue

Understanding the viscoelastic properties of plantar soft tissue under dynamic conditions is crucial for assessing foot health and preventing injuries. In this work, we document an in vivo device, employing the principles of dynamic mechanical analysis (DMA), which, for the first time, enables in situ, real-time multidimensional mechanical characterization of plantar soft tissues. This device overcomes the limitations of conventional ex vivo and single-DOF testing methods by integrating three sinusoidal mechanism-based multi-DOF dynamic testing modules, providing measurements of tensile, compressive, shear, and torsional properties in a physiological setting. The innovative modular design integrates advanced sensors for precise force and displacement detection, allowing for comprehensive assessment under cyclic loading conditions. Validation tests on volunteers demonstrate the device’s reliability and highlight the significant viscoelastic characteristics of the plantar soft tissue. The example dataset was analyzed to calculate the storage modulus, loss modulus, loss factor, and energy dissipation. All design files, CAD models, and assembly instructions are made available as open-source resources, facilitating replication and further research. This work paves the way for enhanced diagnostics and personalized treatments in orthopedic and rehabilitative medicine.