Low-Cost, High-Sensitivity Paper-Based Bacteria Impedance Sensor Based on Vertical Flow Assay

• Published in: Chemosensors 2023-04, Vol.11 (4), p.238
• Main Authors: Long, Yifan, Ai, Zhehong, Zhang, Longhan, Zhang, Han, Jiang, Jing, Liu, Gang Logan
• Format: Article
• Language: English
• Subjects: Bacteria; bacterial detection; Biological assay; Biosensors; Chains; Charge transfer; Design; Diffusion coating; Diffusion effects; Diffusion layers; E coli; Electrodes; Electron beams; Equivalent circuits; Evaporation; Food; Food safety; Gold coatings; Impedance measurement; Low concentrations; Low cost; Melt temperature; Membranes; Methods; on-site detection; Onsite; paper-based electrode; portable sensor; Principles; Production costs; Researchers; Safety and security measures; Sensors; Shadow masks; Smartphones; Spectrum analysis; Three dimensional printing; Water quality
• ISSN: 2227-9040; 2227-9040
• DOI: 10.3390/chemosensors11040238

This study proposes a low-cost, portable paper-fluidic vertical flow assay bacterium counter with high accuracy. We designed sensors with low fabrication costs based on e-beam evaporation and three-dimensional printing based on the impedance measurement principle. Interdigitated (IDT) electrodes were coated on the filter membrane by e-beam evaporation with a shadow mask. We could print wafer-scale frames with low melting temperature three-dimensional-printing materials for confining liquid bacterial samples within the IDT sensing region. This novel fabrication technique significantly reduced the chip’s cost to less than 1% of that of silicon-based chips. Two equivalent circuit models were proposed for different concentration ranges to analyze the principle of paper-based impedance bacterial sensors. We proposed an improved model based on the Randles model for low concentrations by considering the leaky double-layer capacitor effect and spherical diffusion from the nano-structural electrodes of the gold-coated filter membrane. The phenomenon in which charge transfer resistance, Rct, declines at high concentration ranges was found and explained by the pearl chain effect. The pearl effect could cause a false-negative at high concentrations. We modeled the pearl chain effect as an R and C, connected parallel to the low-concentration model. When users properly applied both models for analyses, this sensor could quantitatively measure cell concentrations from 400 to 400 M per milliliter with superior linearity.