Tensile acoustic rheometry for characterization of viscoelastic materials

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

• providing, by a first ultrasound transducer, an excitation tone burst of short duration to a freestanding sample, the excitation tone burst being focused at an interface of the freestanding sample and inducing a perturbation in the freestanding sample, the perturbation being characterized by an initial deformation or displacement of the interface followed by free oscillatory motion of the freestanding sample;
• providing, by a second ultrasound transducer, a plurality of short pulses to the freestanding sample at the interface, the plurality of pulses being 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 freestanding sample;
• detecting, by the second transducer, the echoes and providing electrical signals indicative of the detected echoes to one or more processors;
• determining, by the one or more processors, a displacement as a function of time of the interface from the detected echoes;
• determining, by the one or more processors, a frequency spectrum of the free oscillatory motion of the freestanding sample from the displacement as a function of time of the interface;
• and
• determining, by the one or more processors, one or more viscoelastic properties of the freestanding sample, based on a mathematical model that relates the one or more viscoelastic properties of the freestanding sample with a measured oscillation frequency and a damping of the freestanding sample, which are determined from the displacement as a function of time of the interface.