Interactions, Structure, and Microscopic Response: Complex Fluid Rheology Using Laser Tweezers

Abstract

Optical trapping techniques are emerging as significant research tools in complex fluids, offering the ability to probe nano‐ and microscopic interactions, structures, and responses that govern the rheology of complex fluids. In combination with real‐space imaging, microstructural response of these fluids can be directly and quantitatively correlated to imposed microscopic stresses and strains. Thus, laser tweezers are enabling us to bridge multiple length scales in colloid and polymer rheology and should be highly useful for investigating the mechanisms of linear and nonlinear rheology. In this article, we briefly review the theory and practice of using optical traps in complex fluids. We discuss the characteristics of the gradient force trap, practical concerns in trapping experiments, and applications, including measurements of micromechanics and microrheology in colloid and polymer gels.