Passive wireless smart-skin sensor using RFID-based folded patch antennas.

Folded patch antennas were investigated for the development of low-cost and wireless smart-skin sensors that monitor the strain in metallic structures. When the patch antenna is under strain/deformation, its resonance frequency varies accordingly. The variation can be easily interrogated and recorded by a wireless reader. The patch antenna adopts a specially chosen substrate material with low dielectric attenuation, as well as an inexpensive off-the-shelf radiofrequency identification (RFID) chip for signal modulation. Since the RFID chip harvests electromagnetic power from the interrogation signal emitted by the reader, the patch antenna itself does not require other (internal) power sources and, thus, serves as a battery-less (passive) and wireless strain sensor. In this preliminary investigation, a prototype folded patch antenna has been designed and manufactured. Tensile testing results show strong linearity between the interrogated resonance frequency and the strain experienced by the antenna. Through experiments, the strain sensing resolution is demonstrated to be under 50 με, and the wireless interrogation distance is shown to be over a few feet for this preliminary prototype. [ABSTRACT FROM AUTHOR]