Graphite flake oscillates at a certain normal load. One flake of the mesa pressed by the probe’s tip (the dark part) is oscillating. Since the frame rate of this video is 10Hz, it looks like a low frequency vibration. The actual frequency calculations are given in SI appendix.
Deli Peng, Zhanghui Wu, Diwei Shi, Cangyu Qu, Haiyang Jiang, Yiming Song, Ming Ma, Gabriel Aeppli, Michael Urbakh, and Quanshui Zheng
PNAS. 2020. 117:12618-12623 DOI: 10.1073/pnas.1922681117