Design Issues for Performance Enhancement in Nanostructured Silicon Oxide Biosensors: Modeling the Frequency Response

Nanostructured silicon oxide impedance biosensors with ordered nanopores promise highly sensitive and selective label-free electrical detection of biomolecules through unique frequency-dependent sensitivity characteristics. Despite these promising experimental results, the fundamental mechanisms controlling the frequency-dependent phenomena and hence the design considerations have not been explored. In this paper, we consistently model the fluid and the solid regions of the sensors and discuss the design issues with respect to the pore dimensions for enhancing the sensitivity, selectivity, and repeatability toward detection of ultralow and moderate concentration of target biomolecules. The simulation results have been validated with experiments. The results indicate that the optimal design of nanoporous silicon oxide biosensors is different from the conventional idea of increasing the surface-to-volume ratio of such sensors. Instead, the design approach is nontrivial and the optimum pore dimensions are dependent on the target biomolecule charge, concentration, and distribution. It has been observed that a figure of merit is essential to design such sensors with improved commercial viability.