Stick-slip control of the Carbopol microgels on polymethyl methacrylate transparent smooth walls

Microgel suspensions such as Carbopol are commonly used as viscoplastic fluid models in fluid mechanics experiments. Polymethyl methacrylate (PMMA) walls are also frequently used in these experiments since they enable flow visualizations via their transparency properties. When sheared with smooth surfaces, the microgels slip on the surfaces and an apparent motion of the fluid occurs below the bulk yield stress tau sub(y). This motion stops at a sliding yield stress tau sub(s). The occurrence of this apparent slip below tau sub(y) can significantly modify the flow features. This article presents a PMMA treatment to inhibit the slip of the Carbopol microgels. The method is simple to perform, independent of the treatment conditions and stable over time.