The parameters that were investigated to achieve enhanced sensor performance were buffer type, antibody attachment method, measurement frequency, electrode layout, and conductive material. A 0.04M PBS (phosphate buffered saline) solution achieves better results compared to a less conductive 0.04M PB (potassium phosphate dibasic) solution. The direct adsorption of anti-E. coli antibodies onto the sensor surface yielded better results than attaching the sensor to a lateral flow test. The resistive component had a greater impact on the detected impedance, therefore an optimal frequency of 1 MHz was identified. Geometrical electrode designs that maximise the resistive change between the electrodes were utilised. Both lower cost silver and bio-compatible gold ink were validated as electrode materials. The impedance change generated by the selective capture of E. coli K-12, ranging in concentration from 103 to 107 colony forming units per millilitre (cfu/ml), showed a detection limit of 105 cfu/ml.
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P. Bezuidenhout, S. Kumar, M. Wiederoder, J. Schoeman, K. Land, T-H. Joubert, "The characterisation and design improvement of a paper-based E.coli impedimetric sensor," Proc. SPIE 10036, Fourth Conference on Sensors, MEMS, and Electro-Optic Systems, 100360L (3 February 2017);