High accuracy measurement of mechanical strain is critical and broadly practiced in several application areas including structural health monitoring, industrial process control, manufacturing, avionics and the automotive industry, to name a few. Strain sensors, otherwise known as strain gauges, are fueled by various nanomaterials, among which graphene has attracted great interest in recent years, due to its unique electro-mechanical characteristics. Graphene shows not only exceptional physical properties but also has remarkable mechanical properties, such as piezoresistivity, which makes it a perfect candidate for strain sensing applications. In the present review, we provide an in-depth overview of the latest studies focusing on graphene and its strain sensing mechanism along with various applications. We start by providing a description of the fundamental properties, synthesis techniques and characterization methods of graphene, and then build forward to the discussion of numerous types of graphene-based strain sensors with side-by-side tabular comparison in terms of figures-of-merit, including strain range and sensitivity, otherwise referred to as the gauge factor. We demonstrate the material synthesis, device fabrication and integration challenges for researchers to achieve both wide strain range and high sensitivity in graphene-based strain sensors. Last of all, several applications of graphene-based strain sensors for different purposes are described. All in all, the evolutionary process of graphene-based strain sensors in recent years, as well as the upcoming challenges and future directions for emerging studies are highlighted.

We demonstrate a MEMS-compatible detector with a single channel that employs chemical vapor-deposited graphene (G _CVD ) in a chamberless, nondispersive infrared gas sensing configuration. The detector, designed to function as a thermistor bolometer, is intricately crafted by integrating serpentine-shaped G _CVD into flexible, epoxy-based SU-8 photopolymer, covering an area of 500 × 500 µ m ² . Experimental evaluations of the detector were carried out at a distance of 30 mm away from the light source within a chamberless setup to assess its performance metrics. The results unveil a peak responsivity of approximately 0.65 V/W for the G _CVD -based detector. This outcome underscores the simplicity of the fabrication process, eliminating the necessity for implementing intricate structures like p-n junctions, surface plasmons, or microcavities. Moreover, the detector demonstrates rapid resistance switching, with an impressive response time of 1.2 s and a recovery time of 1.7 s observed during the electrical chopping of the light source.