Hiroto Chikaura

Textured bearing surface in artificial joints to reduce macrophage activation

Micro slurry-jet erosion has been proposed as a precision machining technique for the bearing surfaces of artificial joints in order to reduce the total amount of polyethylene wear and to enlarge the size of the wear debris. The micro slurry-jet erosion method is a wet blasting technique which uses alumina particles as the abrasive medium along with compressed air and water to create an ideal surface. Pin-on-disc wear tests with multidirectional sliding motion on the textured surface of a alloy counterface for polyethylene resulted in both a reduction of wear as well as enlargement of the polyethylene debris size. In this study, primary human peripheral blood mononuclear phagocytes were incubated with the debris, and it was elucidated that the wear debris generated on the textured surface regulated secretion of the proinflammatory cytokines IL-6 and TNF-α, indicating a reduction in the induced tissue reaction and joint loosening.

Development of a new type of seal system for use in ocean current or tidal power generation

Ocean current or tidal power is a promising renewable resource. For the generation of electricity from them, it is important to construct waterproof system with reducing mechanical energy loss. However, there is no appropriate sealing system that is completely waterproof and low friction. So, we developed a new type of seal system for using in ocean current and tidal power generation. We introduced seal lips made of a polyvinyl formal (PVF). PVF lips were attached to a rotating shaft, and a non-Newtonian, aqueous solution of 3.0wt% polyethylene glycol (PEG) with a molecular weight of 2.0 million was applied as lubrication. This sealing system was low water leakage, less than 0.05ml/h, was recorded throughout the experiment. Mean frictional torque was lower than those with a mechanical seal or an oil seal, both of which are generally used for industrial components. Furthermore, frictional torque was stable, and friction was independent of the speed of the rotating shaft.