High-resolution sensing sheet for damage detection based on large area electronics

Deep concern led to research of reliable, robust and low-cost Structural Health Monitoring (SHM) for civil infrastructure. Traditional sensing technologies are either limited by high cost and insufficient spatial resolution, or rely on complex algorithms that malfunction under varying environmental and loading conditions. Our research demonstrates the need for direct sensing, where anomalies are sensed at close proximity via a dense array of sensors. Reliable early-stage damage detection requires continuous monitoring over large areas of structure, and with high spatial resolution of sensors (e.g. centimeter-scale resolution over several square meters). Technology based on Large Area Electronics (LAE) can enable direct sensing scalable to the level required for SHM. A sensing sheet based on LAE (see Figure 2) that combines high-performance ICs with flexible electronics, was researched. Thin-film strain sensors and control circuits are integrated on the flexible electronics and deposited on a polyimide sheet that is possible to expand to large areas. Signals are sent to ICs through non-contact couples, thus many ICs can be applied with low-cost sheet lamination, allowing measuring and readout over a large number of sensors. At the early stage of this research, crack tests with thin resistive strain sensors are utilized to identify the proper patterns (distance, orientation, etc.) for the layout of sensing elements on the LAE sensing sheet, and indicate an average sensitivity of 0.0404 μm/με. A probabilistic approach based on Monte Carlo simulations is also used to evaluate the probability of minute-crack detection of the innovative LAE sensing sheet. Results of both tests and simulations are presented in this paper, demonstrating the feasibility and benefits of LAE and direct sensing approach for damage detection over large areas of structures.