Multi-layer coils for efficient Transcutaneous Power Transfer

TETS (Transcutaneous Energy Transfer System) has been successfully used for powering medical implants for different purposes such as for neural recordings and drug delivery. Yet, due to their low power transfer efficiency, these devices can cause unacceptable increase in skin temperature limiting their scalability to high power levels. Although, the efficiency of these systems can be improved by increasing coil diameter, in many cases this is not practical due to strict physical constraints on the coil diameter. In this paper, we investigate using multi-layer coils as secondary coils in the TETS to increase the power transfer efficiency, and thus allowing the delivery of the desired power safely for a longer period. Our experiments show a 5× increase in the duration of safe power delivery (not increasing the skin temperature more than 2 C) using multi-layer coils as the secondary coil compared to using single-layer coils even when there is a 50% misalignment in between primary and secondary coils. This increase in duration of safe power transfer is shown to be over 16× more when the coils are aligned. The improvement in the duration of safe power transfer is achieved without increasing the coil diameter and with a coil thickness of 2 mm.