Near-field microwave microscopy for liquid characterization

A near-field microwave microscopy platform for the characterization of liquids is proposed. The technique is based on the association of a network analyzer and an evanescent microwave coaxial probe. The major feature of the system proposed is the development of a broadband tunable matching network inserted between the test port of the network analyzer and the probe. The tunable matching network based on microwave interferometry gives the possibility to achieve a strong electromagnetic coupling between the probe tip and the liquid in the range 1-20 GHz. As a demonstration, the monitoring of the evaporation of small volumes of liquids shows that he system is considerably sensitive to any microscopic level change of liquid volume.