Quantification of impedance and mechanical properties of Zeonor using scanning acoustic microscopy

Abstract

This article explores the potential of Zeonor, a transparent cyclic olefin polymer, for applications in transparent acoustic/photo-acoustic transducers. Despite its widespread use in optics, microfluidics, medical devices, and electronics, Zeonor's acoustic properties remain understudied. To extend this, the current work employs scanning acoustic microscopy (SAM) to obtain its mechanical properties. The signal processing method known as maximal overlap discrete wavelet transform (MODWT) is applied to efficiently break down the acoustic responses of Zeonor. The filtered signal is now time-segmented to obtain the desired signal, containing the characterizing signal feature that predicts the acoustic impedance. Further, the longitudinal and transverse acoustic velocities of the Zeonor are determined using successive peak identification and time-of-flight observations. Moreover, an impedance map is developed using Kriging with a Gaussian variogram, that provides the spatial distribution of impedance. Utilizing these results, the article determines mechanical properties such as shear modulus, Young's modulus, and Poisson's ratio, finding good agreement with literature values. The lower acoustic impedance and optical transparency of Zeonor position it as an ideal material for high-frequency photo-acoustic transducers.