Variation in the viscoelastic properties of polydimethylsiloxane (PDMS) with the temperature at ultrasonic frequencies

Abstract

Polydimethylsiloxane (PDMS) is an organic silicone with a viscoelastic behavior suitable for use in engineering. This material presents substantial changes in its properties depending on the temperature and the flow rate: at high temperatures or high flow rates, it behaves as a viscous liquid; whereas, at low temperatures or low flow rates, it behaves as an elastic solid. The lack of accurate information about the modifications in PDMS under thermal changes affects the design of transducers (both sensors and actuators) based on this material and also their calibration. In this study, 10:1 base-agent mixing ratio was analyzed in a 20 °C to 50 °C temperature range to assess the ultrasonic P-wave properties (velocity, attenuation, and variation of both with the frequency) and hence complex elastic modulii of this material under a temperature dependent environment. P-wave velocity and attenuation were extracted for every temperature step in a 3–7 MHz frequency range which is the typical range for medical applications. Acoustic dispersion of PDMS properties such as velocity and attenuation in a pulse-echo set up were analyzed to also compute attenuation coefficient, temperature and frequency dependent models and complex modulus.