The investigation and regulation of interfacial mechanical of gold have a great theoretical and practice value in the field of biomedicine such as tiny biological devices，which involving many issues about interfacial tribology. In this work, the friction behavior between silica microsphere and gold-coated substrates was studied by the electrochemical atomic force microscopy (EC-AFM) under different applied potential. When the negative potential was applied to the gold surface, the friction force between silica microsphere and gold is increasingly linear with the loads. However, when the positive potential was applied, the increasing rate of friction forces is considerably increased and appears steeply rise with loads, which presents a strong nonlinear rather than linear with loads. We attribute the reason for such nonlinear behavior at a positive potential to the difference in interfacial affinity between silica microsphere and gold at different loads. At positive potentials, the confined ordered icelike water layer at Au/electrolyte interface is capable of hydrogen bonding with the silica microsphere. The pressed depth of microsphere into confined icelike water layer is small when the load is low resulting in a small number of hydrogen bonding, and when the load becomes high, the number of hydrogen bonding increases with the increases of pressed depth until it is saturated. Such interfacial force experiments in liquid provide new insight into understanding the structure and physical properties of water on the charged metal surface, which might inspire the development of biomedicine.

Potential-induced nonlinear friction behavior between silica microsphere and gold surfaces in aqueous solution

2019 Fall National Meeting

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