Fig. 1: Battery-free sensor networks based on near-field-enabled clothing.
From: Wireless battery-free body sensor networks using near-field-enabled clothing
a Illustration of multiple battery-free sensor nodes mounted on the skin and interconnected to a wireless reader through the near-field-enabled clothing. b, c Conventional near-field communication (b) is limited to at most a few centimetres separation between the reader and sensor, while near-field relays (c) enable near-field connectivity upto metre scale in separation. h is vertical distance, d lateral distance, and i current. d Photograph of a smartphone wirelessly powering a sensor node over a relay (40 cm length). e Normalised magnetic field ∣Habs∣ generated by a reader directly above a sensor, reader offset from sensor, and reader interconnected to sensor by a near-field relay. Reader and sensor diameters are 3.1 cm and distances h = 0.5 cm and d = 8 cm. f Power transfer efficiency η as a function of sensor position d relative to the reader without (red) and with (blue) a relay (1 m length). η < 1% in the concatenated region.
