Patent ID: 7980752

Claim:
An apparatus for stirring a liquid comprising: a resonator cell containing therein said liquid and a plurality of microparticles; an ultrasound transducer acoustically coupled to said resonator cell; and a control system including a microprocessor adapted to drive said transducer in a swept-frequency mode by varying a frequency of the driving signal of said transducer in a range from a predefined minimum frequency to a predefined maximum frequency, said predefined minimum and maximum frequencies are selected to include therebetween at least two resonance frequencies of said liquid in said cell, said control system further including a voltage control oscillator adapted to send a driving signal to said transducer through a complex resistor, said oscillator controlled by said microprocessor defining the driving signal frequency of said transducer, said control system further including an amplitude or phase detector adapted to receive the driving signal from said complex resistor and further adapted to provide a feedback signal to said microprocessor indicating changes in electrical impedance of said transducer in vicinity of said resonance frequencies.