A cantilever biosensor exploiting electrokinetic capture to detect Escherichia coli in real time

A cantilever biosensor with integrated electrodes for piezoelectric actuation and electrokinetic capture is used to detect cells in real time. The sandwich electrodes used for electrokinetic capture present advantages over side-by-side electrodes in terms of reducing the gap size between electrodes and the structural mass added to the cantilever. The 5th resonant mode (≈617 kHz) of the biosensor provided a signal-to-noise ratio of 82 within 10 min when E. coli was measured from a stagnant sample with a concentration of 107 cells/ml. The 7th resonant mode (≈1160 kHz) provided a signal-to-noise ratio of 26 within 10 min when E. coli was measured from a flowing sample (400 μl/min) with a concentration of 105 cells/ml. The estimated sensitivity of the 7th resonant mode is 326 fg/Hz based on images of captured cells.