Lin et al. developed a gradient-based colorimetric array sensor

Lin et al. developed a gradient-based colorimetric array sensor (GCAS) for continuous monitoring of gaseous analytes, inclusive of biomarkers of diseases and environmental pollutants, [315] which overcomes the limitations of traditional colorimetric sensors which include single-use due to the fact some color change and binding processes are not reversible and cannot be used for continuous monitoring and require real-time imaging and need to get replaced while exposed to very high concentrations of the analyte. for this reason, to overcome the limitations of the colorimetric sensor, Lin et al. Created a gradient-based calorimetric sensor which can be implemented to parallel sensing of multiple analytes via printing distinctive sensing substances on the same substrate that gas analytes can diffuse into the porous substrate through the opening at the edge and react with the sensing materials. the lateral transfer of analytes throughout the substrate creates color gradients on the measurement elements, and over time these color gradients shift within the direct route in their transfer and GCAS follows and tracks these gradient shifts And concurrently converts to the concentration of analytes in real-time. they incorporated three sensing elements for detection of O3, NO2, and HCHO which are a number of the most common air pollution and might cause diverse diseases including asthma. in this colorimetric sensor, the detection limit for O₃ and NO₂ And HCHO were reported at 12, 25 and 11 ppb, respectively. further, in this study, three analytes had been used for detection, but via increasing the measurement appropriate elements to the intended applications, more analytes can be evaluated simultaneously and continuously.