The flexible pressure sensor is one of the essential components of the wearable device, which is a critical solution to the applications of artificial intelligence and human−computer interactions in the future. Due to its simple manufacturing process and measurement methods, research related to piezoresistive mechanical sensors is booming, and those sensors are already widely used in industry. However, existing pressure sensors are almost all based on negative resistance variations, making it difficult to reach a balance between the sensitivity and the detection range. Here, we demonstrated a low-cost flexible pressure sensor with a positive resistance−pressure response based on laser scribing graphene. The sensor can be customized and modulated to achieve both an ultrahigh sensitivity and a broad detection range. Furthermore, the device possesses the signal amplification property like a mechanical triode under the external pressure bias. Based on its amplification ability, varieties of physiological signals and human movements have been detected using our devices; then, an integrated gait monitoring system has been realized. The reported positive graphene pressure sensor has outstanding capability, showing a wide application range such as intelligent perception, an interactive device, and real-time health/motion monitoring.

Based on the good characteristics of graphene, many physiological signals can be detected by graphene sensors covering the human body. Graphene wearable sensors have great potential in healthcare and telemedicine.

Due to its unique electronic properties and wide spectrum of promising applications, graphene has attracted much attention from scientists in various fields. Control and engineering of graphene's semiconducting properties is considered to be key to its applications in electronic devices. Here, we report a novel method to prepare in situ nitrogen-doped graphene by microwave plasma assisted chemical vapor deposition (CVD) using PDMS (polydimethylsiloxane) as a solid carbon source. Based on this approach, the concentration of nitrogen-doping can be easily controlled via the flow rate of nitrogen during the CVD process. X-ray photoelectron spectroscopy results indicated that the nitrogen atoms doped into the graphene lattice were mainly in the forms of pyridinic and pyrrolic structures. Moreover, first-principles calculations show that the incorporated nitrogen atoms can lead to p-type doping of graphene. This in situ approach provides a promising strategy to prepare graphene with controlled electronic properties.