A Colorimetric Multifunctional Sensing Method for Structural-Durability-Health Monitoring Systems.

A colorimetric multifunctional phototransmittance-based structural durability monitoring system is developed. The system consists of an array with four indium gallium zinc oxide (IGZO)-based phototransistors, a light source at a wavelength of 405 nm through a side-emitting optical fiber, and pH- and Cl-selective color-variable membranes. Under illumination at the wavelength of 405 nm at corrosion status, the pH- and Cl-responsive membrane, showing a change in their color, generates a change in the intensity of the transmitted light, which is received by the phototransistor array in the form of an electrical current. I-ds and R (I-ds/I-pH (12)) are inversely proportional to the pH, which ranges from 10 to 12. When the pH drops from 12 to 10, the magnitude of I-ds and R increases to approximate to 10(3). In the case of Cl detection, I-ds and R (I-ds/I-Cl (0 wt%)) increase nearly 50 times with an increase in Cl concentration of 0.05 wt%, and when the Cl concentration reaches 0.30 wt%, I-ds and R increase to approximate to 10(3) times greater. This multifunctional colorimetric durability sensing system demonstrates considerable potential as a novel smart-diagnostic tool of structural durability with high stability, high sensitivity, and multifunction.