Blind Wireless Beamforming to Power, Heat, and Move

The past decades witnessed a proliferation of wireless systems research that has focused on designing more efficient communication and novel sensing applications. However, another well-known capability of wireless has arguably received less attention: the ability to heat, and more generally, provide energy. As an example, consider the microwave oven, a nearly 50-year-old invention that to this day continues to remain largely similar in capability, blasting energy blindly to re-heat food without advancing significantly in terms of fine-grained heating capabilities. Similarly, the existing energy delivery systems for powering battery-free IoT tags energize its surroundings blindly, constraining the battery-free tags to be detected only at specific checkpoints – a range of 5-15 meters at best. While precise control of wireless signals, also known as beamforming, has been an important solution in improving wireless communication systems’ throughput and signal-noise ratio, these systems have not directly translated to innovations in wireless systems for heating and energy delivery more broadly. 

In this dissertation, we build a suite of blind beamforming systems that deliver precisely controllable wireless energy to battery-free devices (e.g., RFID) and objects (e.g., pizza). First, this thesis describes PushID, a beamforming system that powers battery-free RFID tags at scale. Second, inspired by PushID, we present SDC, a redesigned microwave oven system to heat food in a software-defined and fine-grained thermal trajectory. Further, we build on the same heating principle to develop WASER, which moves electronics-free soft robots using wireless beamforming. Besides these, this thesis demonstrates novel battery-free soft materials that can efficiently harvest wireless energy and be capable of advanced sensing capabilities.