2:30 PM - EQ06.04.04
Role of Interfacial Layers in the Performance of EGOFETs and EGOFET-Biosensors
Larissa Huetter1,Adrica Kyndiah2,Gabriel Gomila1,3
Institute for Bioengineering of Catalonia1,Istituto Italiano di Tecnologia2,Universitat de Barcelona3
Biosensors based on electrolyte-gated organic field-effect transistors (EGOFETs) can transform biological signals into electrical signals with a strong amplification . This amplification allows us to detect small variations of voltages produced by (I) electrically excitable cells or (II) the binding of biomolecules . In the second case, the transistor is then functionalized by recognition layers, such as self-assembled monolayers (SAM) and/or antibodies to detect the presence of antigens in the electrolyte . In both situations, the response of the EGOFET is strongly determined by the processes and modifications taking place at the electrolyte/gate and the electrolyte/semiconductor interfaces, as these determine the behaviour of the electrical output. Functionalized layers at these interfaces result in changes in their distributed capacitance and fixed charges. These modify the conductivity of the semiconductor, which leads to a change in the electrical signal (source-drain current) . Even in non-functionalized EGOFETs, the presence of Stern layers at these interfaces can profoundly affect the EGOFET characteristics. To investigate these effects, numerical simulations constitute an excellent tool since they allow isolating the specific effect of the different physical parameters (a charge, specific capacitance, ionic concentration solution).
In the present work, we present the finite-element numerical modelling of EGOFETs in the Nernst-Planck-Poisson and drift-diffusion frameworks, focusing on revealing the role played by interfacial layers on their performance. We predict the transfer and output current-voltage curves of the EGOFETs for different material properties of the semiconducting material, the geometry of the system, the ionic concentration of the electrolyte, but overall, on the properties of the interfacial layers (charge and specific capacitance). Additionally, we also derive the source-gate capacitance-voltage characteristics. For the different situations, we analyze the distribution of charges and potential across and alongside the EGOFET. We examine the formation of the diffusive layers in the electrolyte and its relevance to form the accumulation layer of charge carries in the semiconductor surface. With these studies, we provide further insight into the physics of these devices, including the formation of the pinch-off. The comparison of the results with existing experimental results or theoretical predictions is performed.
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 Kyndiah, A., Leonardi, F., Tarantino, C., Cramer, T., Millan-Solsona, R., Garreta, E., Montserrat, N., Mas-Torrent, M. and Gomila, G., 2020. Bioelectronic recordings of cardiomyocytes with accumulation mode electrolyte gated organic field-effect transistors. Biosensors and Bioelectronics, 150, pp.111844.
 Torricelli, F., Adrahtas, D.Z., Bao, Z., Berggren, M., Biscarini, F., Bonfiglio, A., Bortolotti, C.A., Frisbie, C.D., Macchia, E., Malliaras, G.G. and McCulloch, I., 2021. Electrolyte-gated transistors for enhanced performance bioelectronics. Nature Reviews Methods Primers, 1(1), pp.1-24.
 Kyndiah, A., Checa, M., Leonardi, F., Millan-Solsona, R., Di Muzio, M., Tanwar, S., Fumagalli, L., Mas-Torrent, M. and Gomila, G., 2021. Nanoscale Mapping of the Conductivity and Interfacial Capacitance of an Electrolyte-Gated Organic Field-Effect Transistor under Operation. Advanced Functional Materials, 31(5), p.2008032.