A Field-Deployable Microfluidic CNT-FET Platform for Direct Monitoring of Multiplexed Respiratory Viruses in Environmental Waters.

Environmental water-based epidemiology (EWBE) has emerged as a critical tool for population-level surveillance of respiratory viruses, yet its potential remains constrained by reliance on centralized laboratory assays that lack rapid, field-deployable capabilities. Here, we report a field-deployable biosensing platform that integrates carbon nanotube field-effect transistors (CNT-FETs) with a microfluidic sample processing module for direct, multiplexed detection of SARS-CoV-2, influenza, and respiratory syncytial virus in raw environmental waters. The microfluidic chip incorporates a hierarchical filtration architecture that removes environmental debris without the need for external pretreatment, enabling the delivery of intact virions to functionalized biosensor surfaces. The platform achieves a limit of detection of 10-17 M for viral surface proteins and 100 TCID50/mL for intact virions, with a total assay time of under 5 min. In a validation study of 24 environmental water samples spiked with virus, the platform demonstrates 100% detection accuracy, with performance comparable to reverse transcription-polymerase chain reaction. By combining ultrasensitivity, multiplexing, and true field-readiness, this work addresses a critical gap between centralized molecular diagnostics and on-site EWBE applications, offering a scalable solution for near-source outbreak surveillance.