Determination of complex shear modulus of microparticles by ultrasonic spectroscopy via resonant scattering analysis

Abstract Resonance scattering occurs when ultrasound interacts with micron-sized particles whose diameter is comparable to the wavelength. Because this phenomenon is sensitive to particle shear elasticity, the frequency spectrum of ultrasonic attenuation allows the determination of the shear modulus using ultrasonic spectroscopy. This study proposes an approximate method to evaluate both shear modulus and viscous loss of dispersed particles by using only measured particle size, density, and the peak position and width of the attenuation spectrum. As a model system, sorbitol-water droplets dispersed in hexadecane were analyzed using a 20 MHz longitudinal transducer covering 10–35 MHz. The droplets gradually solidified from a low-viscosity solution to solid sorbitol particles during drying. The proposed approach successfully captured variations in storage and loss moduli with drying time, providing results consistent with conventional theoretical analyses.