A team headed by the prolific John A. Rogers of the University of Illinois at Urbana-Champaign has unveiled an optical skin sensor that has no battery or wires to power it. Instead, the flexible and stretchable device harvests energy delivered from a nearby smartphone or tablet using magnetic inductive coupling. The readings it obtains are beamed back to the mobile device using near field communication (NFC), an ultra-low method of passing data between nearby devices that you may have experienced when using Apple or Android payment systems.
To show that the power transmission is sufficient and practical enough for clinical and at-home applications, the team demonstrated heart rate monitoring, temporal dynamics of arterial blood flow, temperature, measurement of tissue oxygenation and exposure to ultraviolet light, as well as four-color spectroscopy detecting small changes in skin color.
The energy can be delivered from smaller devices such as smartphones at a fairly short distance, only about an inch or so (~ 2 cm), but larger transmitters can extend that to about a yard (~1 m). This should make it practical for bedridden patients who would have a patch attached to the skin while a power generator located nearby, such as under the mattress, would power it. Moreover, a set of wireless patches such as this can measure a comprehensive set of varied health parameters that currently require dozens of wires in today’s clinical practice.