In modern sensing technology, various devices employ emergent semiconductors, such as organic-based semiconductors, 2D materials, and oxides. These materials form interfaces with wet or liquid substances, including skin, complex liquids, living cells, and food. These interfaces, known as electrical-double-layers (EDLs), are highly charged and behave like capacitors. Minute changes in the impedance of these interfaces can be detected through small signal-impedance measurements. However, probing these capacitive layers using impedance techniques is challenging. Small changes in AC impedance can only be detected if the device structure is appropriately designed. This device design strategy includes careful consideration of the device geometry, dimensions, and electrical properties of the materials used. This text focuses on designing strategies for creating reliable devices capable of probing capacitive electric double layers (EDLs) for sensing purposes. The design of these devices involves meticulous modeling using equivalent circuit networks. It also includes a series of guidelines for designing impedance-based devices. Additionally, the text provides examples of applications in environmental sensing and bioelectronics.