All fluids that exhibit a complex behavior as a result of a non-linear relationship between stress and deformation are considered as complex fluids. This sort of fluid stands between Hooke’s law for an ideal elastic material and Newton’s law of viscosity for an ideal viscous liquid. Thus, complex fluids encompass most synthetic and biological fluids, and, consequently, have a tremendous importance in the success of processes associated with industry and health.
Many interesting behaviors of complex fluids (shear thickening, viscoelasticity, thixotropy, etc.) are consequences of their formulations (macromolecules, particle-particle interactions, particle-molecules interactions, etc.) and bring associated many challenges, such as shelf-life, physico-chemical characterization, or processing. Additionally, the degeneration of some biological fluids is associated with some diseases, which results in a loss of their characteristic complex behavior and, consequently, impairing their performance, as in the case of synovial fluid in the protection of a joint. Moreover, the characteristic length-scale of the flow conditions can also be of extreme importance. In microscale processes, viscoelasticity can lead to flow instabilities at creeping flow conditions, which can, for example, be useful for enhancing mixing or oil recovery processes. Additionally, if the fluid is also sensitive to an external field (magnetic or electric), the complexity is even larger. Nevertheless, even in this latter circumstance, complex fluids can exhibit useful performances from a practical point of view, i.e., ferrofluids, magneto-rheological fluids, and electro-rheological fluids.
Complex fluids have very wide cope of applications from long shelf life formulation, stabilization of dispersions, surfaces/interfaces transformations, microscale process engineering, free surface process operations, to biological processes, building engineering, domestic products, cosmetics, composites, food industry, transportation, porous media and in micellization, liquid crystals, tribology and lubrication, magneto-rheological fluids, viscoelastic fluids, electro-rheological, shear-thickening, yield-stress applications. The usage of complex fluids is widespread and integrated into our daily lives.
Our devices which can help in these interests are: All types of contact angle meters used for solid surface, SITA SurfaSpector, A60, A100, A200, A300, RSD100, for liquid or solutions: SITA tensiometers Dynotetser, t15 Plus, t100, SITA ConSpector, SITA Cleanline ST and for surface cleanliness checking and validation: SITA CleanoSpector, SITA FluoScan 3D, SITA Cleanline CI, Viscometer, Rheometer, etc.