ColorX: fitness tracker-based colorimetric sensor for biochemical applications

Colorimetric sensors are ubiquitous tools that are deployed in various research, academic and on-field diagnostic settings. High accuracy and quick readout capability of these sensors are key for biochemical sensing and medical diagnostics. In this article, we introduce ColorX, a novel colorimetric sensor built by modifying a genetic commercially available fitness tracker. The inbuilt components of a fitness tracker such as a heart-rate sensor, LEDs, photodiodes, transimpedance amplifiers provide a compact and portable form factor. ColorX leverages the bluetooth from the fitness tracker for wireless data transmission to smart phones. As a device validation strategy, ColorX was validated by measuring Nitrates in water. In all our experiments ColorX matched the technical performance of a standard benchspectrophotometer. ColorX was able to achieve excellent sensitivity in measuring nitrates as low as 10mg/ml.