Effect of surface conductivity on the sensitivity of interdigitated impedimetric sensors and their design considerations

• A FEM model is elaborated for 3D-IDE sensors taking into account a surface conductance phenomenon.
• Experimental validation of the model is performed.
• IDE sensors design requirements are formulated.

The use of impedimetric biosensors based on interdigitated electrodes (IDEs) for biochemical applications has gained increased interest during the last two decades. Recently a concept of a 3D-IDEs with insulating barriers separating electrodes digits was introduced. This geometry enhances the sensitivity of the transducer to biochemical reactions at the sensor surface. Although there is an experimental evidence of this increase in the sensitivity, its quantification is currently unstudied. In this work the impact of the geometry on sensitivity of IDEs impedimetric biosensors based on surface conductivity variations is studied. For that a finite elements method (FEM) model that takes into account the surface conductivity phenomena has been developed. Its feasibility has been validated comparing modeled and experimental results obtained in immunochemical reaction of IgG protein. Using this FEM model the increase of sensitivity produced by the presence of a dielectric barrier between the electrodes has been quantified. Moreover, the biosensor response has also been analyzed taking into account different geometrical parameters such as electrode width or separation. Finally, this work proposes the design guidelines for maximizing and improving the sensitivity of IDEs based biosensors.