Novel magnetic stimulation methodology for low-current implantable medical devices

Recent studies highlight the ability of inductive architectures to deliver therapeutic magnetic stimuli to target tissues and to be embedded into small-scale intracorporeal medical devices. However, to date, current micro-scale biomagnetic devices require very high electric current excitations (usually exceeding 1 A) to ensure the delivery of efficient magnetic flux densities. This is a critical problem as advanced implantable devices demand self-powering, stand-alone and long-term operation. This work provides, for the first time, a novel small-scale magnetic stimulation system that requires up to 50-fold lower electric current excitations than required by relevant biomagnetic technology recently proposed. Computational models were developed to analyse the magnetic stimuli distributions and densities delivered to cellular tissues during in vitro experiments, such that the feasibility of this novel stimulator can be firstly evaluated on cell culture tests. The results demonstrate that this new stimulative technology is able to deliver osteogenic stimuli (0.1-7 mT range) by current excitations in the 0.06-4.3 mA range. Moreover, it allows coil designs with heights lower than 1 mm without significant loss of magnetic stimuli capability. Finally, suitable core diameters and stimulator-stimulator distances allow to define heterogeneity or quasi-homogeneity stimuli distributions. These results support the design of high-sophisticated biomagnetic devices for a wide range of therapeutic applications.This work was funded by the Portuguese Foundation for Science and Technology (FCT), through the grant references SFRH/BPD/117475/2016, SFRH/BD/129340/2017 and IF/01089/2015, and by the European Structural and Investment Funds, through the project reference POCI-01-0145-FEDER-031132 and POCI-01-0145-FEDER-007679. It was also support by the TEMA - Centre for Mechanical Technology & Automation (UID/EMS/00481/2013-FCT and CENTRO-01-0145-FEDER-022083) and CICECO - Aveiro Institute of Materials (UID /CTM /50011/ 2013).in publicatio