A Dual-Channel, Interference-Free, Bacteria-Based Biosensor for Highly Sensitive Water Quality Monitoring

Abstract

In this paper, we demonstrated a miniaturized bacteria-based biosensing platform for sensitive, reliable, and practical online monitoring of water quality. Two biosensors were integrated into a dual-channel microfluidic device which operated as a detection and a reference sensor, respectively. By providing a reference-compensated sensing response, the device was capable of minimizing environmental interferences, such as temperature and flow rate, ultimately leading to high sensitivity and reliability in water quality monitoring. We used a microbial fuel cell (MFC) technology as a biosensor for the detection of toxic substances in water. Toxic components inhibit bacterial metabolic activity, generating a distinct change in the current output of the MFC-based biosensor. Each biosensor incorporated a single-chambered MFC with an air cathode, which substantially decreased the device complexity and enhanced the practicability as a real-world application. The miniaturization of the MFC biosensor having a 90- $\mu \text{L}$ microfluidic chamber provided rapid and sensitive sensing responses with a concentration range from 0.003% to 0.075% of formaldehyde in media. By controlling the introduction time of the toxic sample with sequential injection of the fresh media into the detection channel, the biosensor is completely reusable and is potentially applicable to long-term in situ monitoring of water quality.