Mixing at Low Reynolds Numbers by Vibrating Cantilevered Ionic Polymers

The objective of this research was to develop a novel active device for laminar mixing. The mixing device developed herein capitalized on Nafion ionic polymers, which are a class of active materials that are thin, flexible, inexpensive, and readily deployable in an aqueous medium and offer strains up to 5% under a small (<2V) applied voltage. The effect of these deflections on an incident laminar flow is the mixing mechanism explored in this effort. To the author’s knowledge, this high-risk effort presented herein is the first attempt to exploit ionic polymers as an active mixing device. Several different configurations of ionic polymers were tested and Digital Particle Image Velocimetry (DPIV) measurements were obtained. Resulting analysis using a quantitative mixing metric shows that the polymer creates differences in the flow under some of the configurations. Namely, in some actuation cases, a clear increase in mixing potential is observed in the near-polymer regions. Compared to a simple channel increases in mixing potential that ranged from 150% to over 300% were measured. Although these differences are present, they do not appear consistently in the results. However, only a partial set of flow information was obtained from DPIV, and an improved understanding of the effect of these polymers could be developed from additional experiments. Using ionic polymers for laminar mixing could foster the development of a new generation of efficient micromixing devices, which will improve the capabilities and effectiveness of numerous microfluidic technologies that range across biomedical, lab-on-a-chip, separation and sorting technologies and many more.