A system identification model for ultrasonic characterization of a swollen PVA hydrogel

In this paper, the development of an ultrasonic characterization method for Poly-Vinyl Alcohol (PVA) hydrogel incorporating diffraction effects is purposed. The Lommel integral, diffraction correction procedure, is applied to the model. Nonlinear least square algorithm, iterative computation in forward model, is employed to minimize the error of the predicted parameters efficiently. To validate the model, the ultrasonic signal is measured in the reflection mode experiment. The system consists of PVA hydrogel as a testing sample immersed in water tank and 10 MHz unfocused piston transducer. Before the transducer is utilized to generate the ultrasonic beam, the alignment between sample and transducer must proceed to get the maximum spectrum of the ultrasonic incident beam. The properties of PVA hydrogel in the experimental results are shown in density, dispersion and thickness in micron scale. Finally, the purposed model has potential to estimate other parameters such as the scatterer size in future work.