This chapter depicts two research findings about nondestructive mechanical stimulation for analyzing interfacial molecular motion by a quartz crystal microbalance (QCM), a micro-mass analysis technique, highlighting polymer dynamics observed at the solid interface. The gelation behavior at the interface and the gelation temperature of methylcellulose (MC) aqueous solution were elucidated as a function of distance from the electrode surface. MC chains were restricted its mobility and aggregation during the sol–gel transition due to adsorption on the electrode surface. Secondly, the glass transition temperature, specifically on buried interfaces, was employed to elucidate the thermal molecular motion of polystyrene. These studies strengthened the understanding of interfacial dynamics and enabled the nondestructive and precise evaluation of molecular motion characteristics at interfaces using a cost-effective, versatile technology known as QCM, consequently allowing interface research for various researchers.