In this article, we present the design and validation of a non-contact scanning system for the development of a three-dimensional (3D) model of moist biological samples. Due to the irregular shapes and low stiffness of soft tissue samples, the use of a non-contact, reliable geometry scanning system with good accuracy and repeatability is required. We propose a reliable 3D scanning system consisting of a blue light profile sensor, stationary and rotating frames with stepper motors, gears and a five-phase stepping motor unit, single-axis robot, control system, and replaceable sample grips, which once mounted onto the sample, are used for both scanning and mechanical tests. The proposed system was validated by comparison of the cross-sectional areas calculated based on 3D models, digital caliper, and vision-based methods. Validation was done on regularly-shaped samples, a wooden twig, as well as tendon fascicle bundles. The 3D profiles were used for the development of the 3D computational model of the sample, including surface concavities. Our system allowed for 3D model development of samples with a relative error of less than 1.2% and high repeatability in approximately three minutes. This was crucial for the extraction of the mechanical properties and subsequent inverse analysis, enabling the calibration of complex material models.

Tissues, such as skin, bones, and tendons, exhibit a piezoelectric effect, which may be an important phenomenon in terms of tissue renewal and regeneration as well as the possibility of modifying their mechanical behavior. In this article, we present the design and development of an in-house system for the precise measurement of electrical potentials and mechanical properties of tendons. The system was validated using tendon fascicle bundles derived from positional as well as energy-storing tendons from various adult mammals (porcine, bovine, and deer samples). The presented system is able to capture changes in elastic and viscoelastic properties of tissue as well as its time–voltage response and, thus, may be used in a broad spectrum of future studies to uncover factors influencing piezoelectric phenomena in tendons. This, in turn, will help to optimize current methods used in physiotherapy and postoperative treatment for effective tendon recovery.

Calcification is a prevalent condition that alters mechanical and structural properties of soft tissues. While significant efforts have been devoted to the characterisation of tendon mechanics, little work has been done so far on understanding the impact of calcification on tissues such as tendons. In this work, we investigate the influence of cycling loading and forced fluid flow on the mechanical and structural properties of tendon fascicle bundles of varying interfascicular matrix (IFM) content at an early stage of calcification. The calcification process was modeled using sample incubation in concentrated simulated body fluid. To evaluate the biomechanical responses of the tendon over the course of calcification, we compared four sets of samples incubated for 7 days in simulated body fluid, forced fluid flow and under cyclic uniaxial loading against a non-incubated control. Mechanical and structural properties were investigated using uniaxial tests, scanning electron microscopy and inductively coupled plasma optical emission spectroscopy. The study revealed that the initial phase of calcification causes an increase in the elasticity, as well as a drop in the normalized value of hysteresis for both IFM-rich and IFM-poor regions of the tendon. However, the relaxation behavior of the tissue remained unchanged during calcification proving that calcium phosphate deposits do not affect the IFM viscoplastic behavior but tissue viscoelasticity instead, which is manifested by a change in hysteresis. The greatest changes in stiffness are observed for statically incubated samples, while cyclically loaded samples were the most susceptible to fibril damage although they did not demonstrate the greatest increases in elastic modulus. The results presented in this work show that the calcification process modifies the collagen-matrix interactions, which leads to a change in their mechanical properties depending on the loading conditions. These findings contribute to our understanding of the pathogenesis of tendinopathy and have the potential to assist in the identification of effective treatment strategies for calcification-induced disorders.

Calcification is a prevalent condition that alters mechanical and structural properties of soft tissues. While significant efforts have been devoted to the characterization of tendon mechanics, little work has been done so far on understanding the impact of calcification on tissues such as tendons. In this work, we investigate the influence of cycling loading and forced fluid flow on the mechanical and structural properties of tendon fascicle bundles of varying interfascicular matrix (IFM) content at an early stage of calcification. The calcification process was modeled using sample incubation in concentrated simulated body fluid. To evaluate the biomechanical responses of the tendon over the course of calcification, we compared four sets of samples incubated for 7 days in simulated body fluid, forced fluid flow and under cyclic uniaxial loading against a non-incubated control. Mechanical and structural properties were investigated using uniaxial tests, scanning electron microscopy and inductively coupled plasma optical emission spectroscopy. The study revealed that the initial phase of calcification causes an increase in the elasticity, as well as a drop in the normalized value of hysteresis for both IFM-rich and IFM-poor regions of the tendon. However, the relaxation behavior of the tissue remained unchanged during calcification proving that calcium phosphate deposits do not affect the IFM viscoplastic behavior but tissue viscoelasticity instead, which is manifested by a change in hysteresis. The greatest changes in stiffness are observed for statically incubated samples, while cyclically loaded samples were the most susceptible to fibril damage although they did not demonstrate the greatest increases in elastic modulus. The results presented in this work show that the calcification process modifies the collagen-matrix interactions, which leads to a change in their mechanical properties depending on the loading conditions. These findings contribute to our understanding of the pathogenesis of tendinopathy and have the potential to assist in the identification of effective treatment strategies for calcification-induced disorders.