The unstable capillary flow of the micellar system formed by cetylpyridinium chloride 100 mM/sodium salicylate 60 mM (CPyCl/NaSal) in tridistilled water was studied in this work using a combination of particle image velocimetry (PIV) and rheometrical measurements. The experiments were run in a pressure controlled capillary rheometer at a temperature of 26°C and covered all the different flow regimes occurring in the nonmonotonic flow curve characteristic of micellar solutions. First, we show the suitability of the PIV technique to study the unstable capillary flow of this micellar system. Then, and more important, we provide evidence of the development of shear banding and the velocity profiles for the different flow regimes, including the transition to the high shear branch because of spurt. The velocity profiles at low shear rates exhibited a Newtonian behavior, followed by a still Newtonian with apparent slip up to the onset of spurt. There was a jump of one order of magnitude in the shear rate with a transient of a few minutes once spurt was triggered. The velocity profiles obtained during the transition to the high shear rate branch were plug-like, with a large increase in the velocity close to the capillary wall. When the transition was completed, the velocity profiles corresponding to the high shear rate branch showed the development of a shear band close to the capillary wall, whose thickness increased along with the shear rate. Finally, the true flow curve reconstructed from the velocity profiles provided additional evidence of the existence of a shear band that grows from the capillary wall

Lubricants are materials able to reduce friction and/or wear of any type of moving surfaces facilitating smooth operations, maintaining reliable machine functions, and reducing risks of failures while contributing to energy savings. At present, most worldwide used lubricants are derived from crude oil. However, production, usage and disposal of these lubricants have significant impact on environment and health. Hence, there is a growing pressure to reduce demand of this sort of lubricants, which has fostered development and use of green lubricants, as vegetable oil-based lubricants (biolubricants). Despite the ecological benefits of producing/using biolubricants, availability of the required raw materials and agricultural land to create a reliable chain supply is still far from being established. Recently, biomass from some microalgae species has attracted attention due to their capacity to produce high-value lipids/oils for potential lubricants production. Thus, this multidisciplinary work reviews the main chemical-physical characteristics of lubricants and the main attempts and progress on microalgae biomass production for developing oils with pertinent lubricating properties. In addition, potential microalgae strains and chemical modifications to their oils to produce lubricants for different industrial applications are identified. Finally, a guide for microalgae oil selection based on its chemical composition for specific lubricant applications is provided.