Capacitive Biosensing of Bacterial Cells: Sensitivity Optimization

Capacitive biosensors are promising tools toward detection of bacterial cells. However, their sensitivity remains insufficient compared with more conventional techniques. To understand how to optimize it, we propose a complete and quantitative analysis of the sensitivity of capacitive biosensors using a previously developed 2-D numerical simulator based on Poisson-Nernst-Planck equations. All key parameters of the electrolyte, bacterial cell, and electrode design are investigated, studied, and optimized. For each, an analytical expression relating the sensitivity to the parameter of interest is given. The guidelines and design tools, provided throughout this paper for the designer of capacitive biosensors, are eventually demonstrated by improving the sensitivity of our device under test by a factor of 4. Discussions based on experimental values and analytical models are provided throughout this paper.