The strain dependence of conductance of monolayer graphene has been studied experimentally here. The results illustrate the notable transitions: the slight increase, the dramatic decrease, and the sudden dropping of the conductance by gradually increasing the uniaxial strain. The graphene conductance behaves reversibly by tuning of the elastic tensile strain up to 4.5%, while it fails to recover after the plastic deformation at 5%. The change in conductance due to strain is surprisingly high, which indicates the potential applications in electromechanical devices.

We report the high performance vertical ultraviolet (UV) photodetectors based on single ZnO nanowire (NW) sandwiched between two graphene sheets. The photocurrent on-off ratio, rising time, and recovery speed of our UV detectors are 8 × 10², 0.7 s, and 0.5 s, respectively, which are significantly improved compared to the conventional ZnO NWs photodetectors. The improved performance is attributed to the existence of Schottky barriers between ZnO NW and graphene electrodes. The graphene/ZnO NW/graphene vertical sandwiched structures may be promising candidates for integrated optoelectronic sensor devices.

There is an emergent demand for high-flexibility, high-sensitivity and low-power strain gauges capable of sensing small deformations and vibrations in extreme conditions. Enhancing the gauge factor remains one of the greatest challenges for strain sensors. This is typically limited to below 300 and set when the sensor is fabricated. We report a strategy to tune and enhance the gauge factor of strain sensors based on Van der Waals materials by tuning the carrier mobility and concentration through an interplay of piezoelectric and photoelectric effects. For a SnS₂ sensor we report a gauge factor up to 3933, and the ability to tune it over a large range, from 23 to 3933. Results from SnS₂, GaSe, GeSe, monolayer WSe₂, and monolayer MoSe₂ sensors suggest that this is a universal phenomenon for Van der Waals semiconductors. We also provide proof of concept demonstrations by detecting vibrations caused by sound and capturing body movements.