Incubation-free detection of bacteria cells by using droplet-based impedance sensing

In this study, we have demonstrated the capability of droplet-based impedance sensor as a cost-effective, simple and rapid bacterial quantification assay. By using evaporation to concentrate and amplify the ions released by bacteria cells, the detection limit of classical non-Faradic impedance sensors is improved by two orders of magnitude. Further, the time-multiplexing capability of DNFIS (achieved by continuous impedance monitoring as the droplet evaporates) significantly reduces the data variability. We showed that through capturing the conductance modulation inherited to bacteria cells suspended in a low conductivity solution, they can be quantified within ca. 20 min which is ~ 10-50 times shorter than the growth-based assays, as summarized in Fig. 3(b).