Silicon-on-insulator based thin film resistors for quantitative biosensing applications

Field-effect based semiconductor devices for the label-free detection of molecular interactions represent a promising development for biosensor applications. Recently, several such devices have been presented for the direct electrical detection of nucleic acids and proteins. However, a detailed and quantitative understanding of experimental observations is still elusive in most cases. Here we employ a recently introduced Silicon-on-Insulator (SOI) based field-effect sensor for the label-free detection of molecules by their intrinsic charge. We present a theoretical description for the quantitative analysis of the sensor response. A capacitor model was developed which accounts for dielectric effects as well as for Debye screening by mobile ions within the layers of molecules bound to the surface. We successfully applied the model to the detection of charged peptides and multilayers at the functionalized sensor surfaces. The electrical detection of the adsorption of bovine serum albumin (BSA) to the sensor surface is demonstrated and can be explained in terms of a dipolar orientation of the bound molecules.