Force spectroscopy on an interface of water and liquid gallium by frequency modulation atomic force microscopy

Abstract Since the liquid/liquid interface is a variety of reaction fields, its high-spatial-resolution analysis is crucial. In this paper, we report the force spectroscopy on a liquid gallium/aqueous solution interface using atomic force microscopy (AFM). For stable analysis of the liquid/liquid interface, a probe-scan-type AFM with a qPlus sensor was developed. By using the frequency modulation technique, conservative and dissipative interactions were separately detected. As a result, a step-like change in resonance frequency corresponding to the conservative interaction was detected on the interface. This was well explained by the conical shape of the tip and the interfacial energy change. The energy dissipation change on the interface was more obscure than the frequency shift change. This result suggests that the detection of conservative interaction is preferable for interfacial analysis of liquids with large surface tension but small viscosity differences, such as liquid Ga and aqueous solutions.