Stretchable strain vector sensor based on parallelly aligned vertical graphene.

The development of wearable strain sensors for human-machine interface has attracted considerable research interests. Most existing wearable strain sensors were incapable of simultaneously detecting strain amplitudes and directions and they failed to fully record stretching vectors that occurred on the body. Graphene and graphene-derived materials have been utilized to construct wearable strain sensors with excellent electrical sensitivities. While the growth techniques of planner graphene and vertical graphene (VG) have been established, the fabrication of VG aligned in parallel within a larger area has not been previously achieved. Here parallelly aligned VG (PAVG) in a large area were successfully fabricated and constructed as a wearable strain vector sensor. The PAVG was fabricated via inductively coupled plasma chemical vapor deposition (ICPCVD) assisted by metal inducers. The as-fabricated sensor was electrically anisotropic due to the profiles of the VG nanosheets aligning in parallel. Therefore, the sensor could simultaneously and sensitively detect the direction and the amplitude of the strain vectors with excellent accuracy. Application of this strain vector sensor for human-sensor interface to identify the stretching directions and amplitudes of finger joints was also demonstrated. This work established the fabrication methodology of graphene with unique vertical and parallel-alignment morphology. This study introduced the new opportunity of developing wearable sensors that could fully detect multi-directional human actions.