Laser‐Scribed Graphene–Polyaniline Microsupercapacitor for Internet‐of‐Things Applications

Abstract The push toward smart technologies and the Internet‐of‐Things (IoT) demands the development of miniaturized energy storage devices. Herein, a facile and scalable strategy is presented, based on laser reduction of graphene oxide into graphene followed by electrodeposition of polyaniline (PANi), to fabricate a substrate‐free supercapacitor. The fabricated supercapacitor is part of a flexible multifunctional integrated system comprising a thin‐film humidity sensor, a resistor, and a near field communication (NFC) antenna for IoT‐linked wireless communication with a smartphone. The integrated sensory system shares laser‐scribed graphene (LSG) as the same electrode material for all the components (supercapacitor, sensor, resistor, and NFC antenna). The symmetric LSG‐PANi||LSG‐PANi supercapacitor with wireless charging capability exhibits a near record‐high energy density of 0.407 mW h cm −3 , and excellent power density of 196 mW cm −3 , along with an outstanding rate capability (enduring high rates of over 1 V s −1 ). As a humidity sensor, the device demonstrates high resistance changes from 2000 kΩ at 0% relative humidity (RH) to 497 kΩ at 100% RH (15 kΩ per RH%) with a sub‐second scale (0.87 s) response time. This research paves the way for limitless applications of IoT across a wide spectrum of fields from healthcare to chip‐based electronics to environmental monitoring.