Towards Sensing Sheets Based on Large Area Electronics

The need for reliable and inexpensive Structural Health Monitoring (SHM) of civil structures and infrastructure is rapidly increasing. However, today’s SHM technologies are based on sparsely-spaced sensors that do not allow reliable early detection of anomalies at locations of even modest distance from the sensors. This form of indirect damage detection raises the need for complex localization and sensing algorithms to overcome the limited resolution. The hypothesis of the presented research is that by substantially increasing the sensor response to local anomalies (i.e., increasing spatial resolution of sensors to a centimeter-scale over several square meters), direct sensing leads to improved reliability in damage detection. Technologies based on Large Area Electronics (LAE) can enable direct sensing and can be scaled to the level required for SHM. Thin-film strain gauges and control circuits are integrated on the flexible electronics and deposited on a polyimide sheet that can cover large areas. At the present stage of this research, crack tests with strain gauge sensors are used to study the layout of sensing elements on the LAE sensing sheet. Additionally, a characteristic identification test is carried out to evaluate alternative designs for sensing elements based on thin film transistors. The general concept of sensing sheets based on LAE (see Figure 1) and the results of both tests are presented in this paper, demonstrating the feasibility and benefits of LAE and the direct sensing approach for damage detection over large areas of structures.