Morphologically modulated laser-patterned reduced graphene oxide strain sensors for human fatigue recognition

Laser heating provides an effective method to produce thermally reduced graphene oxide (rGO), it can also pattern the designed layout on the surface of graphene oxide (GO) during the reduction process. In this work, we demonstrated a flexible strain sensor based on the morphologically modulated laser-patterned reduced graphene oxide (LPG) film with a one-step process. Compared with the strain sensor using flat patterned rGO (0%–1.2%) and curved-grid patterned rGO (CGPG) (0%–4.1%), the strain sensor based on rectangular-grid patterned rGO (RGPG) have highest gauge factor (GF), up to 133 under 2.7% of physical deformation. Meanwhile, the RGPG strain sensors exhibit extraordinary linearity in a relatively large range of deformation (0%–2.7%) and excellent endurance for over 1000 stretching-releasing circles. The RGPG strain sensor was used to monitor human fatigue. By analyzing eye blinking frequency and duration, it is possible to evaluate the fatigue level. We anticipate that the RGPG based strain sensor, prepared via a relatively simple and cost-effective process, may open up a broad spectrum of practical applications, such as driver fatigue evaluation and smart monitoring of human body movements. (paper)