Effect of hydrofluoric acid treatment on the contact time dependence of adhesion force at silica/silica interface revealed on AFM

[Display omitted] •Contact time dependence of adhesion force is related to relative humidity (RH), repeated contacts, and surface treatment.•The force on untreated silica becomes dependent due to repeated contacts and exposure at 90% RH.•Hydrofluoric acid treatment has a hindering impact on contact time dependence. The behavior of adhesion force with contact time has not been fully clarified and requires further investigation. Silicon cantilevers were employed to measure adhesion forces on untreated and hydrofluoric acid (HF) treated silica surfaces with an atomic force microscope (AFM) at relative humidities (RH) of 10 % to 90 % to investigate the behaviors. The results testify that the dependence has a connection with RH, repeated contacts, and surface treatment. The force on untreated silica is time-independent at RHs of 10∼80 % and becomes dependent due to the coupling effect between repeated contacts and exposure at 90 % RH. Nevertheless, the behavior of HF-treated silica remains constantly time-independent, regardless of this coupling effect. HF treatment has a hindering impact on contact time dependence. Besides, the transition cannot be observed through repeated contacts at either 90 % or 10 % RHs. For the independent forces on both surfaces, they can exhibit various behaviors with repeated contacts at different RH ranges. These conclusions help study adhesion mechanism and to some extent provide insights into addressing adhesion failure issues in micro and nano-scale mechanical systems.