PNIPAAm-functionalized flexible microchip for rapid detection of surface microbial contaminants

The detection of surface microbial contaminants faces several critical challenges, including disconnection between sampling and detection steps and time-consuming. To overcome these limitations, we developed an innovative integrated microfluidic system that combines bacterial sampling, transfer, concentration, and detection within a single chip platform. The microchip architecture consists of a thermos-responsive flexible sheet incorporating poly(N-isopropylacrylamide) (PNIPAAm) gel micropillar arrays for efficient bacterial capture and thermal-triggered release, and a PDMS cover layer with an optimized canopy-shaped microchannel design for sequential bacterial transport, fluorescent labeling, and in situ concentration/fluorescence detection. To verify the system's functionality, Staphylococcus aureus (S. aureus) was employed as a model organism for testing the microchip detection platform. Under optimized conditions, the sampling and the elution efficiency of S. aureus on stainless steel sheet were up to 75.6% and 88.4%, respectively. The detection limit of S. aureus was 5.15 × 10³ CFU/cm², and the entire process was completed in < 45 min. This integrated microfluidic system performs continuous surface microbial sampling and detection, reducing processing time by 32-fold compared to conventional swab-based methods. The platform offers a rapid, integrated, and highly efficient solution for bacterial detection for surface microbial contaminants, with promising applications in food safety, medical hygiene, and environmental monitoring.