Graphene-Based Flexible Sensors for Respiratory and Airflow Monitoring

Flexible devices have been rapidly developed and applied in various applications. However, there have been few reports on printable graphene-based sensors with customized structures and properties capable of respiratory and airflow monitoring. In this study, a graphene-based flexible sensor with a conical microdot array (GSCA) made by the direct-ink writing 3D printing method for real-time personal signals and air-coupled detection is reported. GSCA 3D structures with microdot features on the sensing layer can deliver a fast response of below 60 ms and improve the sensitivity by 32.4% (26–78 kPa), 800% (78–102 kPa), and 600% (102–160 kPa) by adjusting the printing parameters. The sensor exhibits a low detection limit of 11.4 Pa and a large detection range with a linear sensitivity of 1.4–509 kPa. The spider leg-like micro-/nanofibers between two adjacent microdots contribute to electron transport and airflow sensing. The results show the feasibility of the graphene-based sensor with dots to recognize air strength and direction for respiration and airflow. Further validation of the GSCA in real-time personal monitoring demonstrates the potential for multitasking wearable sensors.