In a recent study published in Nature Communications, a research team led by Prof. GUO Guangcan from the University of Science and Technology of China (USTC) of the Chinese Academy of Sciences developed nanomechanical resonators based on a graphene substrate, and made nanoresonators slidable across clamping points.
Clamping conditions determine the motion of a vibrating object. This principle inspires not only the invention of musical instruments, but also the creation of different types of mechanical resonators at the nanoscale. Among them, the nanomechanical resonators, with advantages of light weight, high frequency and tunability, are usually fixed to a supporting substrate. However, it remains a challenge to modulate the dynamics of nanomechanical resonators via other fixing methods.
Graphene based sliding nanomechanical resonator (Image by Prof. GUO’s team)
In previous work, the researchers developed nanomechanical resonators by pre-fabricating substrate, preparing electrodes, and transferring a thin membrane of few-layer graphene (FLG). On the resonators, the graphene could slide on the supporting electrodes.
In this study, the researchers found that the resonant frequency of the device depended on the magnitude of the applied gate voltage as well as the way it was applied.
To elucidate this finding, they proposed a sliding nanomechanical oscillator model. They discovered that increasing the gate voltage would promote the stress of graphene, which boosted the resonant frequency, and the quasi-static pulling force produced by a gate voltage decreased the resonant frequency. The competition between the two mechanisms induced the occurrence of a frequency loop. The experimental results were accurately reproduced by the research team using theoretical calculations.
Besides, the researchers found that the area of the frequency loop was proportional to the amount of energy loss due to friction during sliding.
This work provides insight into investigating nanoscale friction and opens up possibilities for realizing new fixing methods at the nanoscale.
(Written by CHEN Yehong, edited by YAN Min, USTC News Center)
