Grant: Discovery Grants Program - Individual

The goals of my research program are to discover and understand the remarkable properties of waves in complex mesoscopic materials, and to develop and use new ultrasonic techniques, based on our knowledge of wave scattering, to probe their structure and dynamics. Mesoscopic materials are characterized by internal structures, at intermediate or mesoscopic length scales, that govern their macroscopic properties and performance. Their importance lies in the enormous potential for manipulating mesostructures and the interactions between them to tailor and optimize materials for society's current and future needs. Realizing this potential will be facilitated by understanding the wave physics of these materials, in which the waves may be scattered many times before leaving the medium and exhibit many fascinating wave phenomena. Examples range from strikingly large variations in wave speeds caused by strong resonant scattering (when a pulse can even appear to travel so quickly through a sample that its velocity is negative) to the complete inhibition of wave propagation that may occur in very strongly scattering samples when waves become localized. Waves in periodic structures, known as photonic crystals for light and phononic crystals for sound, also exhibit unusual effects, such as negative refraction and remarkable focusing properties. We will use innovative ultrasonic techniques, developed in our laboratory, to study such wave phenomena for acoustic and elastic waves (sound). Because of the nature of our detectors, the unique ways in which sound interacts with matter, and the possibility of interpreting our data using new theoretical models, significant advances in understanding the novel wave properties of mesoscopic materials are likely to result from these experiments, leading also to new ultrasonic spectroscopies for materials characterization and process control. Some of the mesoscopic materials that we intend to study include phononic crystals, porous materials, foams, particulate and bubbly suspensions, and aerated food biomaterials.