Genome Technology Center

Modeling of Field-Effect Biosensors

Clemens Heitzinger
University of Vienna, Austria

BioFEDs (biologically sensitive field-effect devices) are field-effect biosensors with semiconductor transducers. Their device structure is similar to an ISFET (ion-selective field-effect transistor), but the surface of the transducer is functionalized with receptor molecules. Conductance modulations of the transducer after binding of the analyte to the surface receptors provide the detection mechanism. The main advantage of BioFEDs is label-free operation.

In recent experiments, DNA strands and tumor markers were detected by silicon-nanowire devices. Despite the experimental successes, a quantitative theory to explain the functioning of the biosensors and to understand the experiments has been missing. The modeling of the biosensors is complicated by the fact that they consist of a biomolecular and a nanoelectronic part with different length scales, yet both parts have to be considered self-consistently.

We present our models for the quantitative analysis of BioFEDs, which are centered around a multi-scale model involving homogenized interface conditions for the Poisson equation for cylindrical and planar geometries (i.e., nanowires and nanoplates). Simulation results show that not only the surface charge density, but also the dipole moment density of the biofunctionalized surface layer has significant influence on the conductance of the transducers. The simulation results also show how the conductance variations can be qualitatively and quantitatively explained by a field-effect.

Bio sketch:
Clemens Heitzinger received the master's degree in applied mathematics and the doctorate degree in technical sciences from the Technical University of Vienna, Austria. After positions as a research associate at Arizona State University (mathematics) and at Purdue University (EE), he is now an assistant professor of mathematics at the University of Vienna, Austria. His research interest is the modeling and simulation of bio- and nanotechnological devices.

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