Structural engineering of graphite network for ultra-sensitive and durable strain sensors and strain-controlled switches

Highly sensitive strain sensors and switches are essential components to wearable electronics in many emerging applications such as personal health monitoring, human–machine interaction, smart robots and intelligent control system. Herein, we report a new highly-anisotropic graphite framework (HAGF) for creating strain sensors and switches with high flexibility, stretchability and sensitivity. The highly anisotropic three-dimensional (3D) graphite structure was fabricated via a facile, low-cost and scalable expansion of commercially-available graphite papers. By controlling the orientation structure and thickness of HAGF, the contact area and switchable conduction path can be tailored to create strain sensors and switches based on HAGF/PDMS composites to achieve a tunable gauge factor between 1.3 and 379, an ultra-high ON/OFF ratio in the order of 1035 with tunable critical switching strain (8 % ∼ 50 %), an excellent long-term repeatability of over 1000 cycles at a peak strain of 50 %, and a stretchability up to 100 %. The potentials of the new sensors and switches are demonstrated by pairing them with the smartphone for tracking and recognition of human motions, offering a new solution to a wide range of portable devices and mobile applications.