A water activity analyzer is a device designed to determine the water activity of samples, whether solid or liquid. Water activity (aw) characterizes the proportion of free, unbound water in a sample that is available for chemical reactions and microbial growth. For pure water the activity is 1, while for a completely dry sample it is 0. Determining water activity is critical in many areas as it affects the stability, storage and microbial safety of products.
In the context of energy storage research, especially for studies of highly concentrated aqueous electrolytes, water activity is of particular importance. Since water activity is included in the Nernst equation, it directly determines the thermodynamic window of electrolyte stability, which is important to consider when selecting electrode materials.

To control and study water activity, our laboratory uses an Aqualab TDL analyzer. This device is equipped with a tunable laser diode (TDL), which generates a laser beam less than one nanometer wide, tuned to the absorption band of water. Thanks to this, TDL is able to measure water molecules with the highest accuracy, regardless of the presence of volatile substances such as soy sauce, gasoline or tobacco in the sample. The accuracy of the readings is so high that even the activity of water in pure alcohol can be measured.

Features of Aqualab TDL include its ability to measure quickly in less than five minutes, which saves significant time compared to other water activity measurement methods that require up to an hour for analysis. The device is easy to use, requires no calibration and is ready to measure in just five minutes, with low maintenance costs and no moving parts.