Laser-Induced Graphene as Versatile Sensing Electrodes for Extended-Gate Field-Effect Transistors

Laser-induced graphene (LIG) stands out as a promising nanomaterial for applications in high-sensitivity, low-cost, and disposable chemical and biological sensing. However, LIG’s metallic properties and weak field effect pose challenges to its integration into high-performance field-effect transistor (FET)-based sensors. This study presents an innovative approach wherein a LIG electrode, created through laser scribing on polyimide (PI) material, serves as a replicable sensing electrode that connects to the gate of a reusable metal-oxide-semiconductor FET (MOSFET) transducer. We implemented pH- and sodium-sensitive FET sensors employing two different LIG sensing electrodes: pristine LIG for pH sensing (30.9 mV/pH) and ion-selective membrane-coated LIG for sodium-ion sensing (−46.9 mV/dec). Various configurations of LIG-based FET sensors were explored to demonstrate the flexibility and versatility of our method, including direct laser scribing on diverse PI materials such as PI adhesive tape, PI-insulated Ag wire, and flexible printed circuit boards (FPCBs). Our findings highlight that LIG sensing electrodes, characterized by their ample surface area, cost-effectiveness, and disposability, are highly compatible with FET-based chemical sensors.