Biosensor response from target molecules with inhomogeneous charge localization

We analyzed the sensor response from aptamer-modified carbon nanotube thin film transistors that adsorb immunoglobulin E (IgE) with an inhomogeneous charge distribution. The net charge of the target molecules within the Debye length reflects the polarity of the electrical sensor signal. The complicated sensor response, which depends on the Debye length, can be interpreted by two kinds of adsorption states considering the influence of steric hindrance by previously adsorbed IgE molecules. These results explain the anomalous behavior of the sensor response in previous reports and pave the way to control the dynamic range.