Resonant acoustic rheometry for characterization of soft viscoelastic materials

A method for performing an acoustic rheology measurement, the method comprising:

• providing, by a first ultrasound transducer, an excitation tone burst to a sample with a defined surface area, the sample in a cylindrical-shaped chamber well, the excitation tone burst being focused at a focal position at an interface of the sample and inducing a perturbation on the interface, the perturbation being characterized by an initial deformation or displacement of the interface followed by free oscillatory motion on the interface;
• providing, by a second ultrasound transducer, a plurality of short pulses to the sample at the focal position, the plurality of pulses being confocal and collinear with the excitation tone burst and synchronized, in time, to impinge upon the interface after the excitation tone burst, to receive, from the interface, echoes responsive to the initial displacement and the following oscillatory motion of the interface;
• detecting, by the second transducer, the echoes and providing electrical signals indicative of the echoes to a processor;
• determining, by the processor, a displacement as a function of time of the interface from the detected echoes;
• determining, by the processor, a frequency spectrum of the free oscillatory motion on the interface from the displacement as a function of time of the interface;
• determining, by the processor, resonant properties of the interface, including a resonant oscillation frequency and damping of the interface, from the displacement as a function of time of the interface;
• and
• applying, by the processor, a hydrodynamic model and determining one or more viscoelastic properties of the sample or one or more intrinsic properties of the sample based on measured spectral properties of the interface.