Highly Sensitive and Reusable Membraneless Field-Effect Transistor (FET)-Type Tungsten Diselenide (WSe<sub>2</sub>) Biosensors

In recent years when the demand for high-performance biosensors has been aroused, a field-effect transistor (FET)-type biosensor (BioFET) has attracted great interest because of its high sensitivity, label-free detection, fast detection speed, and miniaturization. However, the insulating membrane in the conventional BioFET, which is essential in preventing the surface dangling bonds of typical semiconductors from nonspecific bindings, has limited the sensitivity of biosensors. Here, we present a highly sensitive and reusable membraneless BioFET based on a defect-free van der Waals material, tungsten diselenide (WSe<sub>2</sub>). We intentionally generated a few surface defects that serve as extra binding sites for the bioreceptor immobilization through weak oxygen plasma treatment, consequently magnifying the sensitivity values to 2.87 × 10<sup>5</sup> A/A for 10 mM glucose. The WSe<sub>2</sub> BioFET also maintained its high sensitivity even after several cycles of rinsing and glucose application were repeated.