Ultrasonic characterization of single drops of liquids

A apparatus for ultrasonically characterizing a single droplet of a liquid, which comprises in combination:

• a. a transducer having an open surface;
• b. a reflector having a substantially planar surface, the planar surface of said reflector being spaced-apart a chosen distance from, and disposed opposite to the surface of said transducer such that the droplet is held therebetween by surface tension only;
• c. means for applying ultrasonic excitation having a chosen frequency to said transducer, whereby standing waves are generated in the droplet;
• and
• d. means for measuring the electrical impedance of said transducer, from which electrical impedance, the droplet is characterized.

A method for ultrasonically characterizing a single droplet of a liquid, which comprises the steps of:

• a. applying ultrasonic excitation having a chosen frequency to the droplet using a pair of transducers spaced a chosen distance apart where the droplet is suspended in between the tranducers by surface tension only, whereby standing waves are generated;
• in the droplet;
• and
• b. detecting the generated standing waves from which waves, the droplet is characterized.