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The influence of relative humidity (RH) on adhesion forces demands clarification. Adhesion forces at silica/silica and silica/graphene interfaces were measured on an atomic force microscope to investigate the evolution behaviors with RH and the contact time dependence at a certain RH. For the silica/silica interface, the adhesion force at a location by decreasing RH is independent of RH, but increases as a whole with RH both at a location and in the force volume mode by increasing RH. However, for the silica/graphene interface at a location, the adhesion force remains unchanged with RH as a whole by reducing RH and tends to decrease as a whole by increasing RH. In the force volume mode, the adhesion force at the silica/graphene interface is independent of RH. For the silica/silica interface, the adhesion force increases logarithmically with dwell time at a low RH and remains unchanged at a high RH. However, for the silica/graphene interface, the force is not dependent on RH at low and high RHs. The results can serve to further understand the mechanisms and behaviors of adhesion forces and promote the anti-adhesion design for small-scale silicon-based structures.

The adhesion forces between two silica surfaces were measured by using an atomic force microscope with different experimental parameters in air to investigate the dynamic behavior of a confined liquid. Results show that the adhesion force is time-dependent and increases at first sharply and then slightly with dwell time until saturation is reached, with a long equilibrium time. This behavior is well explained by a dynamic meniscus model, in which a liquid bridge grows gradually because of liquid film flow with a large viscosity. Also, the large viscosity was attributed to the formation of orthosilicic acid and subsequent polymerization. With repeated contacts, the liquid bridge changes into two droplets on both surfaces after separation. The liquid in both forms can be controlled to flow into or out of the contact zone by the experimental parameters to achieve tailored adhesion forces. If the liquid of previous contact remains in the contact zone, the adhesion force increases with repeated contacts and then reaches saturation, which can also be explained by the model qualitatively. However, if the liquid droplets vanish before the next contact, the adhesion force usually decreases or remains unchanged. More liquid will be collected with larger contact times. Meanwhile, the droplets remaining on the surfaces get smaller until they vanish without a contact. Moreover, both piezo velocity and scan distance can be used to control the proportion of contact time. In addition, a viscous force should be considered with a large retraction velocity. The changing trend and magnitude of adhesion force depend on the experimental parameters and their coupling effects. The results may facilitate the anti-adhesion design of small-scale silicon-based systems.