Electric field controlled superlubricity of fullerene-based host-guest assembly

Controlling friction by the electric field is a promising way to improve the tribological performance of a variety of movable mechanical systems. In this work, the assembly structure and microscale superlubricity of a host-guest assembly are effectively controlled by the electric field. With the help of the scanning tunneling microscopy (STM) technique, the host-guest assembly structures constructed by the co-assembly of fullerene derivative (Fluorene-C-60) with macrocycles (4B2A and 3B2A) are explicitly characterized. Combined with density functional theory (DFT), the distinct different assembly behaviors of fullerene derivatives are revealed at different probe biases, which is attributed to the molecular polarity of the fullerene derivative. Through the control on the adsorption behavior, the friction coefficient of host-guest assembly is demonstrated to be controllable in the electric field by using atomic force microscopy (AFM). At positive probe bias, the friction coefficient of the host-guest assembly is significantly reduced and achieves superlubricity (mu(min) = 0.0049). The efforts not only help us gain insight into the host-guest assembly mechanism controlled by the electric field, but also promote the further application of fullerene in micro-electro-mechanical systems (MEMS).