BPS2026 – Label-free identification of bacteria and beads via micropore translocation dynamics

Micropore-based resistive pulse sensing is a powerful label-free technique for analyzing the single-particle translocation events. As an analyte passes through the pore, the application of a potential bias across the pore causes a transient change in the ionic current. The current-time signatures, particularly the dwell time and the blockade shape, carry rich information about the size, morphology, and mechanical properties of the translocating entities. In this study, we explore how dwell time and signal morphology can be harnessed to differentiate between spherical beads and various bacterial species, offering a potential tool for rapid microbial identification and particle classification. In terms of passive analytes, we translocated beads of two different sizes—1 and 2 μm in diameter. The blockade events are symmetrical in shape, which justifies the spherical shape. On the contrary, the active analytes like Escherichia coli ( E. coli ) and Pseudomonas aeruginosa (PA), which are rod-shaped, showed asymmetrical blockade events. We performed COMSOL multiphysics simulations, which also show the dependency of the blockade current on the shape of the analytes. The amplitude of the events for E. coli and PA is nearly similar due to their similar dimensions. But for the beads, we observed that the amplitude of 2-μm beads is almost 1.5 times more than that of 1-μm beads. Further studies are underway to use the micropore translocation dynamics to observe the effect of antibiotic treatment on the bacterial cells. It can be used as a potential tool for the detection of circulating tumor cells from the blood cells based on shape and size electrical profiling. Also, it can be used in the identification and quantification of microbial contamination in water sources, and has an application in water purifiers.