Photovoltaic Energy Harvesting for Millimeter-scale Systems
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The Internet of Tiny Things (IoT2) based on mm-scale sensors is a transformational technology that opens up new capabilities for biomedical devices, surveillance, micro-robots and industrial monitoring. Energy harvesting approaches to power IoT2 have traditionally utilized thermal energy, mechanical vibrations and radio frequency electromagnetic radiation. However, the achievement of efficient energy scavenging for IoT2 at the mm-scale has been elusive. In this presentation, I show that photovoltaic cells at the mm-scale can be an alternative means of wireless power transfer to mm-scale sensors for IoT2, utilizing ambient indoor lighting or intentional irradiation of near-infrared (NIR) LED sources through biological tissue. GaAs photovoltaic cells at the mm-scale can achieve a power conversion efficiency of more than 30% under 850 nm NIR irradiation at 1 µW/mm2, and around 20% under white LED illumination at 580 lux through the optimized device structure and sidewall/surface passivation studies, which guarantees perpetual operation of mm-scale sensors. Furthermore, monolithic GaAs photovoltaic modules offer a means for series-interconnected cells to provide sufficient voltage (> 5V) for direct battery charging, and bypass needs for voltage up-conversion circuitry. Finally, I demonstrate monolithic PV/LED modules at the µm-scale for brain-machine interfaces, enabling two-way optical power and data transfer in a through-tissue configuration.
Chair: Professor Jamie Phillips
Remote Access: https://bluejeans.com/781814411