Researchers at the University of Michigan developed the smallest solar sensor ever created–the dimensions are 2.5 x 3.5 x 1 millimeters. The sensor can run nearly perpetually if periodically exposed to reasonable lighting conditions as its only limiting factor is battery wear-out. The sensor’s solar cells, processor, and battery are all compacted into a tiny frame measuring just 9-cubic-millimeter.
The sensor has been designed to spend most of its time in sleep mode, waking briefly every few minutes to take measurements. The designers claim that the average power consumption of the sensor is less than 1 nanowatt. The sensor is based on an industry-standard ARM Cortex-M3 processor that uses about 2000 times less power in sleep mode than its most energy-efficient counterparts.