A highly sensitive portable piezoresistive sensor with a fast response time in an extended linear working range is urgently needed to meet the rapid development of artificial intelligence, interactive human-machine interfaces, and ubiquitous flexible electronics. However, it is a challenge to rationally couple these figures of merit (sensitivity, response time, and working range) together as they typically show functionally correlative behavior in the sensor. Here, we aim at introducing the hierarchical pores across several size orders from micro- to larger scale into the intrinsically flexible graphene-based electrode materials that overcome this limitation of the sensor. We achieved a flexible sensor with a prominent sensitivity of 11.9 kPa-1 in the linear range of 3 Pa to ∼21 kPa and a rapid response time of 20 ms to positively monitor the pulse rate, voice recognition, and true force value for biomedical and interactive human-machine interface application assisted by an analog-digital converter. More interesting is the carbon-nanotube-doped graphene that also served as the electrode in the waterproof supercapacitor to actively drive the sensor as a whole flexible system. We believe our findings not only offer a general strategy for the graphene-based platform in flexible electronics but also possess other intriguing potential in functional application such as the heat dissipation component in electron devices or seawater filtration in environment application.
Keywords: graphene; hierarchical structure; piezoresistive sensor; pulse rate; supercapacitor.