Liquid‐Gated Transistors Based on Reduced Graphene Oxide for Flexible and Wearable Electronics

Abstract Graphene is regarded as the ultimate material for future flexible, high‐performance, and wearable electronics. Herein, a novel, robust, all‐green, highly reliable (yield ≥ 99%), and upscalable technology is reported for wearable applications comprising reduced graphene oxide (rGO) as the electroactive component in liquid‐gated transistors (LGTs). rGO is a formidable material for future flexible and wearable applications due to its easy processability, excellent surface reactivity, and large‐area coverage. A novel protocol is established toward the high‐yield fabrication of flexible rGO LGTs combining high robustness (>1.5 h of continuous operation) with state‐of‐the‐art performances, being similar to those of their rigid counterparts operated under liquid gating, including field‐effect mobility of ≈10⁻¹ cm² V⁻¹ s⁻¹ and transconductance of ≈25 µS. Permeable membranes have been proven crucial to operate flexible LGTs under mechanical stress with reduced amounts of solution (<20 µL). Our rGO LGTs are operated in artificial sweat exploiting two different layouts based on lateral‐flow paper fluidics. These approaches pave the road toward future real‐time tracking of perspiration via a simple and cost‐effective approach. The reported findings contribute to the robust and scalable production of novel graphene‐based flexible devices, whose features fulfill the requirements of wearable electronics.