抄録
The implanted device targeted here is an artificial sphincter that utilizes a shape memory alloy (SMA). It receives drive energy through a transcutaneous energy transmission system which utilizes the electromagnetic coupling of a coil pair. This artificial sphincter bends according to the metamorphosis of the SMA. Temperature control in the living body is necessary to heat the SMA to its metamorphosis-completion temperature. Taking advantage of the lack of need for a power supply for the sensor drive, we examined a method of controlling electric power to be transmitted by a control transformer consisting of a thermosensitive magnetic ferrite core. The temperature of the SMA is controlled by referring the Curie point of the ferrite attached to the SMA. The metamorphosis-completion temperature of the SMA that we used is 55°C. The purpose of this system is automatic prevention of SMA overheating when the SMA temperature rises to 55°C. Actually, because the electric power transmitted through the transformer decreases smoothly with a rise in temperature around the Curie point, the temperature of the SMA stabilizes at a balance point where the heat radiation of the SMA balances overheating by the heater.
