RF-Powered Silicon-MEMS Microsensors for Distributed and Embedded Sensing Applications

In this paper, the concept and experimental results of microwave-powered silicon microsensors for distributed and embedded sensing applications are presented. This is the first report of a microsensor device integrated with RF-DC power converter on the same chip. The integrated sensors are fabricated by silicon-MEMS (Micro Electromechanical Systems) technology. This time, 'fuse-type strain detector', and 'water-leakage sensing switch' are fabricated by silicon micromachining. Driving power of the integrated microsensors is provided as a remote RF-electromagnetic wave at 1.29 GHz/1.45 GHz, and received at the rectenna circuit on the microsensor. In the fabrication experiments, high-performance surface mount devices (SMD) are integrated on the silicon microchip to realize the highest power efficiency. Mount holes of SMDs were formed by Deep-RIE of silicon with MEMS sensor structures without any additional process steps. Fabricated rectenna and sensors are successfully evaluated with LED mounted for signal output. The battery-less microsensor chip was successfully driven by a 10 W/1.29 GHz microwave power. Using a directional antenna as the power emission source, spread of microwave power is limited, and a longer distance of microwave power transmission is obtainable. The RF-powered microsensor node is very promising for various applications, and its conceptual prototype has been successfully fabricated.