Graphene Related Conductive Inks And Their Applications In Printed Sensors

Fabrication of electronic components or circuits by depositing conductive inks on flexible substrates is a preferred method for manufacturing flexible electronics due to its low cost and large scale.In recent years,considerable research has been carried out to synthesize graphene and graphene related hybrid inks for various applications in components and circuits for flexible electronics.However,large scale,good quality,low-cost and environmental-friendly synthetic techniques are required and remains an inevitable challenge for producing and handling graphene based inks for commercial adoption in flexible electronics.In this work,specific ink formulation and preparation methods are comprehensively discussed based on their relevant applications with optimized structures and properties.The main contents are as follows:1.Conductive gravure printing ink by gelation of graphene microsheets(GMs)/polymer dispersions for the application of strain sensor.Strain sensors with large stretchability and high sensitivity are highly desirable because of their potential applications in electronic skins and health monitoring systems.However,achieving strain sensors with both high sensitivity and high stretchability is still a grand challenge.In this section,firstly,by changing the initial concentration of GMs,the optimized GMs/ polymer(PVAc-PVP)composite gel ink with the best conductivity and rheological properties is obtained.Then,a three-part strain sensor based on GMs-Ag nanowires-GMs(GMs-Ag NWs-GMs)is developed via a simple gravure printing process.Due to the overlapping microstructure of GMs and electrical connection of Ag NWs,the sensor can be used to detect stretching deformations with a wide sensing range(up to 90% strain),high sensitivity(a gauge factor of 82.3 to 292),and good reliability and stability(>1000 cycles).Above all,GMs-Ag NWs-GMs sensor achieves both high sensitivity and high stretchability in strain detection.2.Fully Gravure-printed W_O3/ Pt-decorated graphene nanosheets composite sensor for detection of acetone.Acetone gas has been identified as a specific biomarker of diabetes.Therefore,it is demanding to develop selective,low-power,sensitive and flexible devices to detect acetone gas at ppb levels for non-invasive diagnosis of diabetes.However,development of acetone sensors with both high selectivity and high sensitivity at relatively low temperature(<250 ℃)is still a grand challenge.Described herein is a flexible and lightweight chemiresistor made of a thin film based on W_O3/graphene nanosheets decorated with Pt nanoparticles(W_O3/Pt-GNs)composite ink,which were printed onto a flexible polyamide substrate by using gravure technique.In order to study the effect of graphene size on the performance of gas sensing,graphene with two sized such as large-sized graphene microsheets(GMs)and small-sized graphene nanosheets(GNs)were synthesized and used as modified materials incorporated into W_O3-based system.The printed W_O3/Pt-GNs sensor exhibits a high response of 12.2 to 10 ppm acetone as well as a fast gas response /recovery time(14.1/16.8 s)at the operating temperature of 200 ℃.In addition,the printed W_O3/PtGNs sensor is the most excellent selectivity toward acetone reported so far.The sensing performance is attributed to the exposed(002)facets of W_O3 which were not wrapped into GNs,the massive p-n junction active sites at the W_O3/GNs interface,as well as catalytic Pt nanoparticles.In conclusion,the printed W_O3/Pt-GNs sensor achieves the selective and sensitive detection of acetone at relatively low operating temperature.In this paper,the synthesized graphene related conductive inks possess good performance.The printed GMs-Ag NWs-GMs sensor achieves high sensitivity and high stretchability in strain detection.The printed W_O3/Pt-GNs sensor achieves the selective and sensitive detection of acetone at 200 ℃.It provides a reference for the application of graphene based inks in sensors.