Fig. 4: Effective bacteria enrichment and release at low concentrations.

a Location of trapped cells on the chip. Top row shows a bright-field image of the DEP device. Bottom row shows fluorescence images at representative locations along the electrode array, with a full scan available in Supplementary Fig. S5. Scale bar, 200 µm. b Representative time-lapse fluorescence images showing the enrichment of a low bacterial load sample ( ~ 5 CFU/ml in DI water). The sample flow rate was set at 200 μl/min, with a voltage of 40 V at 100 kHz. The input rate was calculated at ~1 cell per minute based on the sample volume delivered. Green arrows indicate newly captured fluorescent bacteria at each time point compared to the previous frame, demonstrating the progressive accumulation of pathogens on the electrode surface. c The captured cell number plotted against the theoretical input bacterial number for various low bacterial load concentrations (2, 4, 8, 23, 41, and 230 CFU/ml in DI water). Linear regression analysis indicates a strong correlation between the captured and theoretical cell numbers. Shaded areas represent 95% confidence intervals. The captured cell number was counted from the time-lapse images. d Fluorescence images showing the DEP chip before and after the release of trapped cells (i.e., small bright dots) upon turning off the DEP power, illustrating the effective release of captured bacteria. Data in (a–d) represent n = 3 independent experiments. Source data for (c) and (d) are provided as a Source Data file.