Dielectrophoretic trapping and impedance detection ofEscherichia coli,Vibrio cholera, andEnterococcibacteria

In this work, a dielectrophoretic impedance measurement (DEPIM) lab-on-chip device for bacteria trapping and detection ofEscherichia coli,Vibrio cholerae, andEnterococcusis 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 forE. coli,V. cholerae, andEnterococcus, respectively. The DEPIM device enables a high detection sensitivity, which requires only a total number of 69 +/- 33E. colicells, 9 +/- 2Vibrio choleracells, and 36 +/- 13Enterococcuscells to observe a discernible change in system impedance for detection. Nonetheless, the corrected limit of detection forEnterococcusis 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.