Optical Microrheology of Soft Complex Materials

Dynamic multiple light scattering (diffusing wave spectroscopy, DWS) has been used to study the viscoelastic properties of soft materials. Several new multiple scattering approaches were implemented to extend the range of application of this optical microrheology technique. Taking advantage of the recently developed “two-cell technique” we show how DWS can be used to investigate the properties of fluid and solid-like complex media. Furthermore, we have significantly extended the range of accessible correlation times to at least 10−8–104 sec using a CCD-based multi-speckle analysis scheme. Excellent agreement is found when comparing the results obtained from DWS to classical oscillatory shear measurements. However, compared to classical rheology, we were able to significantly increase the range of accessible frequencies, thereby opening up a wealth of new possibilities for the study of these fascinating materials. E-mail: [email protected]