Tensile acoustic rheometry for characterization of viscoelastic materials

Abstract

A new acoustic technique, tensile acoustic rheometry (TAR) for performing rheology measurement of a soft viscoelastic material sample is provided. In TAR, an excitation acoustic pulse is applied using a focused ultrasound transducer to a sample material to induce oscillatory motion of the sample. To track this induced motion, high repetition frequency ultrasound pulse-echo technique is used using a co-linear, con-focal ultrasound transducer that detects the backscattered echo signal from a surface or an interface of the sample. The detection ultrasound transducer system converts the echo signals to an electrical signal, and a processor determines a displacement of the interface of the sample as a function of time. The processor also determines the spectrogram, or the frequency spectrum of the dynamic surface movement of the sample material as a function of the time. Viscoelastic properties of the material are then determined from the displacement and the spectrogram measurements.