Zhang Fu-Jian, Chen Yue, Gao Xiang, Liu Zhen, Zhang Zhong-Qiang. Uni-directional self-driving of water droplets on monolayer graphene-covered wedge-shaped copper substrateJ. Acta Physica Sinica, 2021, 70(20): 200202. DOI: 10.7498/aps.70.20210905