Fig. 1. Diagram of the optical setup.

Fig. 2. Schematic diagram of the specimen holder. A 1 mm thick glass plate with a conductive electrode pattern in indium tin oxide (ITO) is separated from a thin cover glass with a spacer. The inset shows a sample of E. coli in urine aligned to the applied electric field between the electrodes.

Fig. 3. Live E. coli bacteria under 500x magnification. (a) No electric field. The bacteria are aligned randomly. (b) Applied electric field in the horizontal direction. The bacteria are aligned to the electric field. (Online only, 2.45 MB) Initially, the movie shows the bacteria randomly aligned. Then, the electric field is applied and the bacteria align along the field. Note the larger bacteria align slower than the smaller bacteria.

Fig. 4. Specimen holder which aligns bacteria in and out of the plane. (a) Schematic diagram of the parallel plate specimen holder. (b) Applied electric field in and out of the plane. Note the line from the upper right to the lower left of the image. The two electrodes are stacked on top of each other and are located to the left of this boundary. Bacteria to the left of this boundary align to the electric field, normal to the image plane, and appear as points. Bacteria that are immediately to the right of this boundary orient to the fringe fields from the electrodes, from the upper left to the lower right of the image. (Online only, 2.47 MB) Initially, the movie shows the bacteria randomly aligned. Then, the electric field is applied and the bacteria align to the field.

Fig. 5. Optical scattering measurements at an angle of approximately 33 degrees. The solid curve shows the increase in the optical scattering when the electric field is turned on (between the vertically dashed lines) for 5·10⁷ CFU/mL live E. coli in urine. The dashed curve shows the same measurement for filtered and sterilized urine with dead E. coli.

Fig. 6. Rise and fall time of the optical scattering measurement at an angle of approximately 33 degrees. (a) Rise time of the bacteria alignment to the electric field is approximately 500 milliseconds. (b) Fall time of the bacteria alignment to the electric field is approximately 1.5 seconds.

Fig. 7. Optical scattering with respect to bacteria concentration and angle of detector. (a) The measurement with 5·10⁷ CFU/mL live E. coli. On average, there is approximately a 20% signal increase with the electric field on versus off. At the detector angle of 20 degrees, the signal increase is approximately 44%. (b) The measurement with 5·10⁶ CFU/mL live E. coli. On average, there is approximately a 5% signal increase with the electric field on versus off. At the detector angle of 15 degrees, the signal increase is approximately 8%.