Liquid contactable colorimetric sensor array for bacteria discrimination

Rapid and reliable detection of bacterial metabolites in liquid culture is critical for early diagnosis of sepsis, yet conventional dye-based colorimetric sensor arrays (CSAs) are hindered by dye leaching and poor interfacial interactions in aqueous environments. Here, we introduce a polydimethylsiloxane-based CSA (PDMS-CSA) platform that overcomes these limitations by leveraging the intrinsic hydrophobicity of PDMS to stably immobilize water-soluble indicator dyes within the polymer matrix. This design ensures direct, unimpeded contact between analytes and sensors, enhancing both sensitivity and reproducibility. The PDMS matrix further contributes by preventing dye leaching while facilitating mass transport of bacterial metabolites such as ammonia (500 μM), hydrogen sulfide (50 μM), and carbon dioxide (1.7 mM) to the immobilized indicators, thereby enabling rapid and robust colorimetric responses. Using this platform, we achieved reliable differentiation between cocci and bacilli within 3 h, demonstrating a capability for rapid, clinically relevant bacterial identification. By combining operational simplicity with high analytical performance in complex liquid media, PDMS-CSAs represent a transformative approach for point-of-care sepsis diagnostics. Beyond sepsis, this strategy offers a versatile framework for the development of next-generation, non-invasive microbial sensor operating platforms with broad translational potential in clinical and environmental monitoring.