Compact and cost-effective autofluorescence sensor for real-time environmental biofilm monitoring

Biofilms, microbial communities embedded in extracellular polymeric substances (EPS), exhibit strong resistance to antimicrobial agents and physical cleaning, making their removal challenging. As persistent sources of contamination, biofilms pose significant challenges in industrial, medical, and environmental sectors. This study presents the development of compact, cost-effective sensor module for real-time biofilm monitoring under ambient light conditions. Using Staphylococcus epidermidis as a model biofilm, autofluorescence properties were analyzed, identifying 285 nm as the optimal excitation wavelength. Five sensor modules were evaluated for sensitivity, linearity, and cost efficiency, leading to the selection of the most suitable photodetector. A prototype was constructed by integrating a 285 nm LED, a photodetector, and a lock-in amplifier (LIA) to minimize environmental light interference. The compact sensor module (90 × 90 × 32 mm) demonstrated stable fluorescence detection under ambient light levels up to 200 lux. This study advances biofilm detection beyond laboratory-based methods, enabling real-time monitoring and management in industrial and everyday environments.