RF Backscatter-Based Sensors for Structural Health Monitoring

There is a growing need for accurate and reliable assessment of conditions of a variety of engineering structures and for monitoring of their performance. Miniaturized, passive, backscatter-based RF sensors with embedded computational capabilities could enable advanced structural health monitoring at high fidelity and at large-scale. Specifically, these RF-powered devices, pervasively embedded and dispersed within the structural material, can sense parameters of interest throughout large volumes of instrumented structure, perform modest local computations to infer structural conditions, and communicate via backscatter modulation while consuming near-zero power. We demonstrate that the backscatter channel phase sensing enables quantification of a size of air gap between two RF sensors embedded in sand. Additionally, we demonstrate the sensitivity of the phase to the strain of the sand.