Table 1.
Summary of the investigated bacterial strains.
Figure 1.
Photographs of microfluidic chip (a) during fabrication, and (b) micrograph of the contraction region of the channel. (c) CAD rendering of the micro channel highlighting the constriction region. (d) Sample inverted fluorescent image of S. mitis SF100 trapping during 3DiDEP. Scale bars are 1 cm (a), and 100 μm (b and d).
Figure 2.
Trapping of bacteria near the constriction.
Fluorescence intensity (arb) (a) and time–lapse images (b) for aggregation of S. mitis SF100, PA14 WT, and PA14 mucA when exposed to a constant voltage difference of 45 V for t = 10–110 seconds. Away from the constriction, electrophoretic force acting on the bacteria dominates over electroosmotic fluid flow and moves the bacteria from right to left towards the negative electrode. Close to the constriction, positive dielectrophoresis pulls the bacteria back into the constriction. Trapping behavior was observed in PA14 mucA and SF100, but not in PA14 WT, while aggregation was only observed in PA14 mucA. The region of integration is shown in (b).
Figure 3.
Analysis of key trapping parameters.
Integrated fluorescence intensity of PA14 WT and PA14 pvrR as a function of time, with representative inverted fluorescent images of PA14 pvrR (a). Voltage was swept at 1 V/s for 100 seconds (e.g. 50 s corresponds to 50 V applied). The response can be characterized by the time at which trapping can first be observed and the rate at which bacteria accumulate. Trapping initiation and bacteria accumulation rate for all ten strains investigated (b). Initial trapping and cell accumulation rate are fitted as shown in the inset. pvrR, mucA, and pelA demonstrate earlier and stronger responses than PA14 WT, while flgK, pilC, and cupA1 exhibit later and weaker responses. Accumulation rates for S. mitis SF100 and PS344 are similar, but PS344 traps earlier (i.e. at a lower voltage).
Figure 4.
Linear sweep trapping intensity varies across strains of bacteria.
Fluorescence intensity as a function of time as voltage was swept at 1/s for P. aeruginosa PA01 WT (a), cupA1 (b), flgK (c), mucA (d), pelA (e), pilC (f), pvrR (g), S. mitis SF100 (h), and PS344 (i) compared to P. aeruginosa PA14 WT.