A Korean institute patented a technology that you can charge your smartphone using your own hand.
Just by naturally holding and using them, may charge your mobile device. The technology uses ultrasound to carry power from a power source to mobile device to be charged. An ultrasonic generator could be used to convert energy to powerful sonic waves which could be conducted through the human skin and transferred to an ultrasonic receiver placed in a mobile device.
To make sure of its quick charging feature, the technology controls the ultrasound generator’s driving frequency and matches impedance of transmitter, intermediate medium and receiver.
As a result, the wireless transmission of energy is done efficiently.
Patent Number – US 9,362,783