Damage characterization often requires direct sensing due to the localization of the anomalous behavior near the cracks. Direct sensing, however, is expensive because of the need to deploy a dense array of individual sensors. Sensing sheets based on Large Area Electronics (LAE) and Integrated Circuits (ICs) are a novel solution to this problem. Such sensing sheets could span several square meters, with a dense array of strain sensors embedded on a polyimide substrate along with the relevant electronics allowing for direct sensing while keeping the costs low. Current studies on LAE based sensing sheets are limited to laboratory experiments. This paper explores the question of suitability of the sensing sheets as a viable option for real-life SHM based on LAE and ICs. Results of laboratory experiments on an aluminum beam are provided to demonstrate the performance of sensing sheets in ideal conditions. Then, the sensing sheets are employed on a pedestrian bridge already equipped with fiber-optic sensors. The strain measurements from the sensing sheets and the fiber-optic sensors are compared and sources of differences are discussed.
In this study, TiO<sub>2</sub> films were deposited using thermal Atomic Layer Deposition (ALD) system. It is observed that asdeposited ALD TiO<sub>2</sub> films are amorphous and not suitable as TFT channel material. In order to use the film as channel material, a post-annealing process is needed. Annealed films transform into a polycrystalline form containing mixed anatase and rutile phases. For this purpose, devices are annealed at 475°C and observed that their threshold voltage value is 6.5<sup>V</sup>, subthreshold slope is 0.35 V/dec, I<sub>on</sub>/I<sub>off</sub> ratios 2.5×106 and mobility value is 0.672 cm<sup>2</sup>/V.s. Optical response measurements showed that devices exhibits decent performance at ultraviolet region where TiO<sub>2</sub> has band to band absorption mechanism.
In order to demonstrate tunable absorption characteristics of ZnO, photodetection properties of ZnO based thin-film transistors are investigated. By controlling the occupancy of the trap states, the optical absorption coefficient of ZnO in the visible light spectrum is actively tuned with gate bias. An order of magnitude change of absorption coefficient is achieved. An optical modulator is proposed exploiting such tunable absorption mechanism.