Abstract:
This paper details the design, characterization, and application of a novel test system for quantifying the viscoelastic mechanical properties of collagen gels, a common extracellular matrix (ECM) scaffold used in tissue engineering. The system features custom-designed culture chambers and a piezoelectric actuator capable of applying precise, cyclic tensile strains while simultaneously measuring the resulting forces. To ensure the validity of the experimental setup, a finite element (FE) model of the culture chamber was created. This biomechanical simulation, which modeled the gel as a hyperelastic neo-Hookean material, confirmed that a uniform strain state existed in the central region of the gel, which is essential for accurate material characterization. Experimental testing was performed on collagen gels of three different concentrations (1.5, 3.0, and 4.5 mg/mL). The results demonstrated that the dynamic stiffness of the gels—a measure of their viscoelastic tangent modulus—increased significantly with higher equilibrium strain, greater collagen concentration, and faster loading frequencies. A key finding was the dramatic difference between the dynamic stiffness and the equilibrium tangent modulus, highlighting that the viscous component dominates the material's response under dynamic loading, accounting for over 90% of the stiffness at 5 Hz. The study also established that the gel's properties remained stable for up to 7 days in culture, providing a reliable baseline for future studies on cell-matrix interactions and the mechanical conditioning of engineered tissues.
