Microfluidic dielectrophoresis device for trapping, counting and detecting Shewanella oneidensis at the cell level.

Shewanella oneidensis, a model organism for electrochemical activity bacteria, has been widely studied at the biofilm level. However, to obtain more information regarding this species, it is essential to develop an approach to trap and detect S. oneidensis at the cell level. In this study, we report a rapid and label-free microfluidic platform for trapping, counting and detecting S. oneidensis cells. A microfluidic chip was integrated with a modified dielectrophoresis (DEP) trapping technique and hole arrays of different hole sizes. By numerical simulation and an elaborate electric field distribution design, S. oneidensis cells were successfully trapped and positioned in the hole arrays. Real time fluorescence imaging was also used to observe the trapping process. With the aid of a homemade image program, the trapped bacteria were accurately counted, and the results demonstrated that the amount of bacteria correlated with the hole sizes. As one of the significant applications of the device, Raman identification and detection of countable S. oneidensis cells was accomplished in two kinds of holes. The microfluidic platform provides a quantitative sample preparation and analysis method at the cell level that could be widely applied in the environmental and energy fields.