Digital image analysis for microfluidic paper based pH sensor platform

pH of fluids is an important indicator in biomedical and environmental studies. Conventional pH analysis techniques are often either instrumentation-intensive, expensive or qualitative in nature. Microfluidics based analytical devices have emerged as powerful alternative to overcome some of the existing limitations. These devices are characterized by low reagent and sample volumes, controlled flow, cost-effectiveness and portability. In this work, we report a microfluidic paper-based lab-on-a-chip pH sensing platform that incorporates passive fluid flow of samples. The colorimetric pH detection is integrated with mobile phone based image acquisition, followed by digital image processing and analysis for quantitative interpretation of data. The images are analyzed using image processing algorithms and color space. Regression analysis of data acquired from digital image analysis was used to evaluate the mathematical model for estimation of pH. The insights gained by this work would prove useful in development and deployment of portable and miniaturized sensors.