Physical Sensors for Liquid Properties

In this contribution, an overview is given of physical sensors for the determination and monitoring of the state of liquids. Basic liquid properties in different energy domains (electrical, mechanical, thermal, and optical) are discussed and their application in sensors is reviewed. Such sensors are useful for bulk fluids, but also for very small liquid volumes such as used in microfluidic devices. In addition, the capability of physical chemosensors for the retrieval of chemical or biochemical information of the liquid is explicated.