(590c) Photorheological Fluids Based on Surfactants and Polymers: Applications in Turbulent Drag Reduction and Microfluidic Flow Control

Raghavan, S. R., University of Maryland
This talk will highlight our work on photorheological (PR) fluids, i.e., fluids whose rheological properties can be tuned by light. A decade ago, we showed for the first time that PR fluids could be created easily using commercially available cationic surfactants and salts (JACS 2007, 129, 1553). This enabled engineers to prepare PR fluids in bulk quantities at low cost, and thus explore applications. We have continued to refine the formulations for PR fluids and can now achieve a million-fold change in fluid viscosity upon shining UV light, which can subsequently be reversed by shining visible light (Soft Matter, 2013, 9, 5025). We have also described alternate designs for PR fluids based on biopolymers such as sodium alginate. Two applications for PR fluids will be discussed in this talk. Firstly, in collaboration with Prof. Jack Zakin at Ohio State University, we have explored the use of surfactant-based PR fluids in turbulent drag reduction (Langmuir 2011, 27, 5806; 2013, 29, 102). Secondly, we have demonstrated a light-activated microfluidic valve, where flow through a microchannel is blocked by irradiating a channel segment with UV light (ACS AMI 2016, 8, 17529). These applications leverage the ability of light to be directed from afar at a precise location and time.