Separation of Escherichia coli K12 from contaminated tap water using a single-stage, continuous flow dielectrophoresis (DEP) device

- Dielectrophoresis was used to separate E. coli cells in drinking water.
- No chemical additives were used to filter the cells.
- Flow rate and voltage showed a significant effect on the separation efficiency.
- Lower medium conductivity exhibited stronger pDEP than higher conductivity medium.

Dielectrophoresis (DEP) is a phenomenon that utilizes an electric field to induce a dipole moment in cells. By applying different fields of magnitude on each dipole, a DEP force is established that leads the cell towards a specific field gradient allowing separation of target cells from its liquid medium. The study explored the potential application of DEP to remove Escherichia coli K12 from tap water samples by observing the relationship among frequency, flow rate, media conductivity, and voltage. A millimeter-sized DEP device in a continuous flow was constructed using polydimethylsiloxane (PDMS) as foundation with a piece of titanium sheet and several titanium wires serving as the electrodes. A frequency generator was paired with an amplifier moderated the frequency and voltage in the electrodes. The combination of 450 μS/cm and 1 MHz showed E. coli cells favoring the pin channel more than the base channel, thereby demonstrating the positive DEP movement. The highest separation efficiency was found to be 47% and 42% under the experimental parameters of 40 V at 100 μl/min and 60 V at 1 ml/min, respectively. With optimization of a scale up device, DEP can be potentially used an alternative and additional step to conventional water treatments.