Ultrafast optical reduction of graphene oxide sheets on colorless polyimide film for wearable chemical sensors

Optically reduced graphene oxide (RGO) sheets were produced on a thermally stable and highly transparent colorless polyimide (CPI) substrate by irradiating intense pulsed light (IPL) on a GO-coated CPI film. These RGO sheets can be used as flexible gas sensing layers for wearable applications. Ultrafast IPL irradiation formed RGO sheets on the CPI film within 4 msec without any damage on the plastic substrate. The IPL-induced RGO (IPL-RGO) sheets exhibited dramatically improved chemical sensing performance toward H2S, C2H5OH, and H-2, while the pristine GO sheets did not show any gas responses. In addition, consistent sensing properties were maintained even after the IPL-RGO sheets on the CPI film were mechanically deformed for 10(4) bending cycles. The gas responses of an IPL-RGO sensor toward H2S, C2H5OH and H-2 were clearly distinguished by pattern recognition based on principal component analysis. Moreover, we successfully integrated our IPL-RGO sensor on a flexible printed circuit board with wireless Bluetooth communication and demonstrated outstanding sensing properties for potential applications in environmental and healthcare monitoring.