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High-accuracy machine learning-based colorimetric pH quantification using a custom-built portable strip-imaging
Ece Minel Bursalı1, Mehmet Akif Özdemir1, Mustafa Şen2
1Department of Biomedical Engineering, Faculty of Engineering and Architecture, Izmir Katip Celebi University, Izmir, Turkey.
Abstract:
Traditional colorimetric pH strips rely on subjective visual interpretation, while camera specifications and lighting variability often influence smartphone-based systems. We developed a compact, machine learning (ML)-enhanced pH sensing platform combining a custom ESP32-S3 device with controlled LED illumination and a mobile application. The system utilizes a 787-sample dataset spanning pH 0-14, extracting 45 statistical features from the red-green-blue (RGB) channels, hue-saturation-value (HSV) channels, and CIELAB color spaces. An AutoML pipeline was used to select an ExtraTreesRegressor model, achieving an [Formula: see text] value of 0.967 and outperforming traditional RGB-based methods ([Formula: see text] = 0.618). The integrated Android application enables real-time, offline pH prediction via Wi-Fi communication. This fully embedded, end-to-end platform eliminates dependency on smartphone cameras and illumination while maintaining high accuracy across the full pH range, making it well-suited for portable pH monitoring in resource-limited settings.
