Challenges and Promises of Near-Field Scanning Microwave Microscopy in Liquid

Near-Field Scanning Microwave Microscopy (SMM), also referred to as Scanning Microwave Impedance Microscopy (sMIM), is a technique that takes advantage of the quasi-static interaction between a probe and a surface to detect and quantitatively measure the electromagnetic properties of a surface, such as dielectric constant and conductivity, with nanometric resolution using a microwave signal. Furthermore, due to the penetrating nature of microwaves, SMM enables the characterization of sub-surface features, potentially allowing for 3D tomography in certain cases. While this method has been successfully applied to analyze novel 2D structures, nanodevices, topological materials, and semiconductors, its application in wet environments—essential for studying liquid-solid interfaces and soft biological samples under physiological conditions—remains a significant challenge. In this talk, we will outline the working principles of SMM, examine the challenges associated with in-liquid operation, and discuss recent advancements, including the development of inverted SMM (iSMM). Additionally, we will explore the necessary steps to transition from qualitative to quantitative measurements in this field.