Ultrasonic Imaging of the Electroacoustic Effect in Macromolecular Gels

The electroacoustic effect occurs in electrolytes and colloidal suspensions. It describes the phenomenon in which a voltage applied to the sample produces an acoustic signal or vice versa. The basic mechanism is that charged particles in the sample have various mobilities due to different masses and viscosities. Under an external voltage they respond differently to the electrical force. This results in an overall acoustic vibration. The electroacoustic effect has been the basis for many measurement tools of solutions and other materials. In this note a method to image macromolecular gel samples using the electroacoustic effect at ultrasound frequencies is presented. Radiofrequency electrical excitation produces ultrasonic signal due to spatial changes in the electroacoustic sonic amplitude of the sample, which is used to construct an image similar to ultrasonography. This method is demonstrated in agar gel and eggwhite protein phantoms. The image contrast mechanism is also discussed.