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Originally introduced by the Material Science community, the Epidermal Electronics is now collecting interest also among Antenna engineers for the potentiality to achieve thin and flexible sensing transponders that are suitable to application over the epidermis. Unlike conventional wearable antennas, which are generally decoupled by the lossy human body by means of spacers or shielding sheets, epidermal tags need to be placed at a very close touch with the skin thus providing poor communication capabilities. This paper investigates, by means of a detailed numerical and experimental study, the performance of an epidermal dual-loop tag for UHF Radiofrequency Identification (RFID) depending on the specific placement over different parts of the human body and for a variety of volunteers. An on-body tuning mechanism is also introduced and demonstrated in real applications at the purpose to improve the tag response and hence to enable the use of a same tag layout for all the UHF RFID bands and for several placement loci.

Magnetic localizers have been widely investigated in the biomedical field, especially for intra-body applications, because they don’t require a free line-of-sight between the implanted magnets and the magnetic field sensors. However, while researchers have focused on narrow and specific aspects of the localization problem, no one has comprehensively searched for general design rules for accurately localizing multiple magnetic objectives. In this study, we sought to systematically analyse the effects of remanent magnetization, number of sensors, and geometrical configuration (i.e. distance among magnets—Linter-MM—and between magnets and sensors—LMM-sensor) on the accuracy of the localizer in order to unveil the basic principles of the localization problem. Specifically, through simulations validated with a physical system, we observed that the accuracy of the localization was mainly affected by a specific angle ($$\theta$$ θ  = tan−1(Linter-MM / LMM-sensor)), descriptive of the system geometry. In particular, while tracking nine magnets, errors below ~ 1 mm (10% of the length of the simulated trajectory) and around 9° were obtained if θ ≥  ~ 31°. The latter proved a general rule across all tested conditions, also when the number of magnets was doubled. Our results are interesting for a whole range of biomedical engineering applications exploiting multiple-magnets tracking, such as human–machine interfaces, capsule endoscopy, ventriculostomy interventions, and endovascular catheter navigation.