Probing charge and dielectric relaxation in protein interactions using atomic field-effect transistor biosensors

The advancement of label-free and rapid-resulting ion-sensitive field-effect transistor (ISFET) biosensors hinges on understanding biomolecular interactions at the interface. While conventional ISFETs excel at charge detection, they struggle with sensitivity to weakly coupled interfacial capacitance due to the relatively thick insulating passivation layer, which protects the chemically active conduction channel from the electrolyte solution. In this work, we adopt chemically inert two-dimensional (2D) materials with electronic processes directly exposed on the sensing surface, thereby allowing for the strongest interfacial capacitance coupling. By combining conductance measurements with capacitance characterization, our results reveal that the protein interactions at the sensor surface undergo dramatic spatial structure evolution, manifested through a slow dielectric relaxation compared to charge kinetics. Therefore, such compact, dual-parametric 2D atomic biosensors are capable of consistently tracking both charge and dielectric properties of analytes within a single device, offering comprehensive quantification of protein interaction kinetics and deeper insights into the underlying sensing mechanisms.