A universal mechanical tester to study biotribology of tissue and biomaterial surfaces

Tribology is a field of science where articulation between two or three surfaces is studied in the form of friction and wear. Friction is quantified in terms of coefficient of friction (µ) and wear in terms of mass loss and generation of debris. When such studies are performed on tissues or biomaterials under mimicked physiological conditions or ex-vivo articulation against tissue, they are referred as biotribology. The population of the western world is becoming older and the trends are to stay active as long as possible. Human motion and activity solely depends on the ability of body parts to move and slide relative to each other, which boils down to articulation (sliding while in contact) at interfaces like cartilage-cartilage, cartilage-meniscus, enamel-gum-mucosa, cornea-eyelid and tendon sheets. In the human body most of these interfaces are lubricated by body fluids like synovial fluid, tear or saliva. Ageing not only causes stiffness of tissue but also imbalance in body fluids causing deterioration in organs and joints function. The loss in function is often restored with the help of prosthesis and implants, which is often accompanied with tribological problems, due to an un-optimized biotic-abiotic interface. Once a biomaterial is introduced in the body it gets covered with a conditioning film, a layer of proteins, glycoproteins and polysaccharides from the adjacent body fluids. Friction, being a surface phenomenon not only depends on the native surface properties of biomaterial like their physico-chemistry and roughness, but also the structure of the conditioning film which would provide lubrication. In order to perform biotribological studies, a versatile equipment is required which can mimic and simulate physiological loading conditions. The equipment should be able to provide enough freedom to mount various different biological specimens and allows different articulation motion. The universal mechanical tester (UMT) is an ideal device because of its rotational and linear reciprocating drives with normal, lateral and torque sensors which unable it to perform friction and wear measurements under all mimicked in-vivo loading situations. By combining UMT with the potentiostat (versaSTAT) we can effectively perform tribocorrosion studies i.e. both potentiodynamic polarization and impedance spectroscopy during articulation. Tribocorrosion is a major problem with metal-on-metal joints. Both UMT and versaSTAT will be used to solve some of the important present day biotribological problems like the need of a biostable artificial meniscus, reduction of wear debris generation and metal ion release from artificial joints, wear-less non-fusion scoliosis correction device and better saliva and tear substitutes for patients with Sjogren’s syndrome. This requires testing of different set of biomaterials which is impossible without proper equipment. The configuration of UMT with its wide load range of 1 mN to 1000 N, capability to perform measurements from the microscale to a complete hip joint and tribocorrosion makes it unique in The Netherlands. As per the supplier the tribocorrosion capability makes it even unique in Europe. The new UMT and versaSTAT will be placed within the Department of Biomedical Engineering, UMCG as a part of the W.J. Kolff institute (WJKI). The WJKI provides a platform for combining clinical and more fundamentally oriented research projects, through the involvement of many departments from the University Medical Center Groningen and the institute i.e. a. Orthopedics; b. dentistry and c. Opthalmology. An array of other equipment like the quartz crystal microbalance (QCM) to study condition film formation, Atomic force microscope (AFM) and AFM coupled to fluorescent microscope (AFM-FM) for tribological characterization of materials at nano-scale are already available to complement the biotribological studies.