Tuning the mechanical properties of polymer-based surrogate materials for articular cartilage and vocal fold repair

The macroscopic biomechanical characteristics of soft and ultrasoft tissues, such as articular cartilage and vocal folds, significantly determine their physiological function. Treatments of widespread tissue degradations due to osteoarthritis in the knee or vocal fold impairment remain an unresolved challenge. For the design of implants for tissue repair after injury or disease, it is key to thoroughly understand the unique biomechanical properties of native tissues and potential substitute materials. We use multimodal mechanical testing methods combined with hyperelastic nonlinear continuum mechanics modeling, and finite element simulations to determine the macroscopic behavior of surrogate materials for human articular cartilage in the knee and human vocal folds. Our cyclic loading experiments reveal qualitative similarities for both tissues and their surrogates, including a nonlinear stress-strain behavior, hysteresis, and conditioning. We demonstrate the tunability of biomimetic and biosimilar stiffnesses of synthetic articular cartilage and vocal fold surrogates through tissue-specific process-material combinations. Our results demonstrate the feasibility of synthetic metamaterials in replicating essential passive biomechanical functions with great potential for future treatment options.