Body-coupled power transmission and energy harvesting

Wireless power transmission and energy harvesting techniques could be used to power and operate devices in, on and around the human body. However, near-field power transmission approaches are limited by distance, and the efficiency of far-field radiofrequency methods is limited by the body shadowing effect. Here, we show that the body-coupling characteristics of electromagnetic waves—which are either artificially introduced or present in the immediate surroundings—can be used to enable a power transmission and energy harvesting method that offers power to locations all around the body. The body-coupled power transmission exhibits a path loss 30- to 70-dB lower than far-field radiofrequency transmission in the presence of body shadowing. The system can recover 2 µW at the head from an ~1.2-mW transmitter placed 160 cm away at the ankle. In the absence of an active power transmitter, we demonstrate placement-independent scavenging of ambient electromagnetic waves coupled onto the human body, resulting in a power recovery of ~2.2 µW from electromagnetic waves of up to −10-dBm on the body. Electromagnetic waves, which are either artificially introduced or present in the immediate surroundings, can couple to the surface of the human body, creating a power transmission and energy harvesting method that can be used to provide sustainable power to wearable devices all around the body.