Highly Sensitive and Wearable In₂O₃ Nanoribbon Transistor Biosensors with Integrated On-chip Side Gate for Glucose Monitoring in Body Fluids

Nanoribbon and nanowire based field-effect transistor (FET) biosensors have stimulated a lot of interests. However, most of FET biosensors were achieved by using bulky Ag/AgCl electrodes or metal wire gate, which have prevented the biosensors from becoming truly wearable. Here, we demonstrate highly sensitive and conformal In₂O₃ nanoribbon FET biosensors with fully integrated on-chip gold side gate, which have been laminated onto various surfaces, such as artificial arms and watches, and have enabled glucose detection in various body fluids, such as sweat and saliva. The shadow-mask fabricated devices show good electrical performance with gate voltage applied using gold side gate electrode and through aqueous electrolyte. The resulted transistors show mobilities ~ 22 cm²V^-1s^-1 in 0.1 x phosphate-buffered saline, high on-off ratio (10⁵), and good mechanical robustness. With the electrodes functionalized with glucose oxidase, chitosan, and single-walled carbon nanotubes, the glucose sensors show very wide detection range spanning at least 5 orders of magnitude and detection limit down to 10 nM. Therefore, our high-performance In₂O₃ nanoribbon sensing platform has great potential to work as indispensable components for wearable healthcare electronics.