A Resonant System for In Vitro Studies Emulating Wireless Power Transfer Exposure at 13.56 MHz

This paper presents the design of a resonant system for in vitro studies to emulate the exposure of a monolayer of cells to a wireless power transfer system operating at 13.56 MHz. The design procedure targets a system, which maximizes the specific absorption rate (SAR) uniformity on the plane where the layer is cultured, as well as SAR efficiency (defined as SAR over the input power), within the size constraints of a standard incubator. Three resonant wireless power transfer systems with different commonly used loop/coil geometries (cylindrical with circular and square cross-sections and annular) were compared with assess the configuration maximizing the considered design criteria. The system performance in terms of reflection and transmission coefficients, as well as generated E- and H-fields, was characterized numerically and experimentally inside the incubator. Moreover, SAR was computed at the monolayer level. The system equipped with cylindrical coils with square cross-sections led to a high electromagnetic field uniformity in in vitro biological samples. In particular, the uniformities in E and SAR at the layer level were within 7.9% and 5.5%, respectively. This was achieved with the variation in H below the usually considered ±5% limit. © 2020 Bioelectromagnetics Society.