Detection beyond Debye's length with an electrolyte-gated organic field-effect transistor

Area of Science:

• Biomedical Engineering
• Materials Science
• Physical Chemistry

Background:

• Electrolyte-gated organic field-effect transistors (EGOFETs) are sensitive electronic devices.
• Detecting biomolecular binding events is crucial for biosensing applications.
• Understanding sensing mechanisms in concentrated solutions is challenging.

Purpose of the Study:

• To investigate the sensing mechanism of EGOFETs in highly concentrated solutions.
• To demonstrate the utility of EGOFETs as biosensors for detecting binding events at extended distances.
• To elucidate the role of Donnan equilibria in the capacitive sensing mechanism.

Main Methods:

• Fabrication and characterization of electrolyte-gated organic field-effect transistors.
• Immobilization of biomolecules on the transistor surface.
• Electrical measurements in highly concentrated electrolyte solutions.
• Analysis of transistor response to specific binding events.

Main Results:

• EGOFETs successfully detected binding events at distances significantly larger than the Debye length.
• The primary sensing mechanism identified was capacitive, not solely charge-based.
• Formation of Donnan's equilibria within the protein layer was confirmed.
• An additional capacitance (CDON) in series with the gating system was observed.

Conclusions:

• EGOFETs offer a robust platform for biosensing in challenging concentrated environments.
• The capacitive sensing mechanism, influenced by Donnan equilibria, broadens the understanding of EGOFET operation.
• This work enables the development of novel biosensors with enhanced detection capabilities.