Dielectrophoretic trapping and impedance detection of Escherichia coli, Vibrio cholera, and Enterococci bacteria

In this work, a dielectrophoretic impedance measurement (DEPIM) lab-on-chip device for bacteria trapping and detection of Escherichia coli, Vibrio cholerae, and Enterococcus is presented. Through the integration of SU-8 negative photoresist as a microchannel and the precise alignment of the SU-8 microchannel with the on-chip gold interdigitated microelectrodes, bacteria trapping efficiencies of up to 97.4%, 97.7%, and 37.7% were achieved for E. coli, V. cholerae, and Enterococcus, respectively. The DEPIM device enables a high detection sensitivity, which requires only a total number of 69 ± 33 E. coli cells, 9 ± 2 Vibrio cholera cells, and 36 ± 13 Enterococcus cells to observe a discernible change in system impedance for detection. Nonetheless, the corrected limit of detection for Enterococcus is 95 ± 34 after taking into consideration the lower trapping efficiency. In addition, a theoretical model is developed to allow for the direct estimation of the number of bacteria through a linear relationship with the change in the reciprocal of the overall system absolute impedance.