A Flexible Virtual Battery: A Wearable Wireless Energy Harvester

Continuous advancements in the domains of biomedical sensors, Internet of Things (IoT) devices, in vivo sensors, and other similar technologies have created a great need to miniaturize portable and end-user devices, especially their powering circuitry. Nearly all devices and sensors require a powering mechanism to obtain, process, and/or transmit information. For example, [1] discusses a flexible gastric battery and a wireless power link that can replace traditional bulky batteries and reduce the size of the wireless capsule. Low-power circuit solutions are of paramount importance for wearable and implantable devices to reduce battery size and improve user comfort [2]. Harvesting the available unused microwave energy from, e.g., Wi-Fi and cellular signals seems a promising solution for replacing a conventional battery with a virtual battery. This term has been used in [3] to describe RF-to-dc converters that are able to power small, portable RF applications for a reasonably long time in the absence of a direct illuminating RF field.