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A transcutaneous signal-transmission system is discussed. We propose the use of cross coils as signal-transmitting coils. A pair of cross coils is placed between power-transmitting pancake coils that transmit power from outside the body to implantable devices, such as ventricular assist devices. Cross coils can cancel the effect of the power-transmitting magnetic fields and transmit signals at the same time. By examining actual-signal transmission, we were able to draw up a guideline on the design of cross coils.

In a transcutaneous energy transmission system for a totally implantable artificial heart, it is necessary that the efficiency of the implantable devices be improved and the temperature rise be minimized. In this paper, we first discuss the properties of Li-ion and Ni-MH batteries for driving an artificial heart, and then consider driving methods for a vibrating flow pump that is used in some electromagnetic artificial hearts. A pump using asymmetrical-wave voltage is 1-4% more efficient than one driven by square-wave voltage.

We investigated the energy transferring system whose temperature rise was reduced below 2 degrees in case of energy transmission of 20 watts. The system was developed for energy consuming implantable devices, such as totally artificial heart (TAH) or multichannel functional electrical stimulation (FES). Electrical energy was transferred inductively through transcutaneous transformer made of amorphous magnetic fibers. We studied push-pull synchronous rectifier circuits for the implanted converter. Figure-of-eight coils were employed for signal transmission.

The authors propose to use an Electric Double Layer Capacitor (EDLC) as an emergency power source for totally implantable medical devices. So far chemical batteries, such as Ni-MH and Li-ion batteries, have been considered as power sources. EDLC needs no control circuit to protect against excess charge and discharge. Furthermore, EDLC can be cycled many times. In these points EDLC is superior to batteries.