Green Group develops new smart fluid

Green Group develops new smart fluid

Carl McIntyre, a research fellow in the Department of Materials Science and Engineering at the University of Michigan, demonstrates the new smart fluid he worked on developing.

Liquids that thicken dramatically when you zap them with electricity are used today as shock absorbers in car brakes and clutches, among other applications. University of Michigan researchers have developed an innovative new "smart fluid" that is cheaper and easier to make than current versions.

Their "electrorheological fluid" flows with the consistency of motor oil in its “off” state, and peanut butter in its “on” state.

Led by Peter Green, professor and chair of Materials Science and Engineering, the researchers were able achieve this functionality from a suspension that was not electrorheologically active by adding cage-shaped nanoparticles that behave like surfactants. Surfactants, a class of compound that includes soap, lower the surface tension of a liquid.

The new suspension is made of just 10 percent of these nanocage filler particles, whereas conventional smart fluids contain between 30 and 50 percent.

When electricity is applied to the new fluid, it thickens up by two orders of magnitude. That’s a similar degree of viscosity change to today’s fluids. But the new substance, in the absence of the field, has a lower viscosity than typical particle-based electrorheological (ER) fluids.

“The advantage of this new system over conventional ER fluids is its very low initial viscosity and cost,” Green said. “Conventional ER fluids exhibit a similar change in viscosity upon application of an electric field.”

This advance comes nearly 25 years after University of Michigan physicist Frank Filisko patented a waterless smart fluid recipe that enabled the technology’s wide adoption. Because water boils away at high temperatures, mixtures that included it were not suitable in automotive applications, for example.

Smart fluids save money because they can replace multiple small moving parts that wear out. They are energy efficient, and can react in milliseconds---faster than solid damping devices.

The paper is titled “Electrorheology of Polystyrene Filler/Polyhedral Silsesquioxane Suspensions.” It is published in Applied Materials & Interfaces. The first author is Ernest McIntyre, a research fellow in the Department of Materials Science and Engineering. Green is the Vincent T. and Gloria M. Gorguze Professor of Engineering and a also professor of macromolecular science and engineering. The university is pursuing patent protection for this technology and is seeking commercialization partners to bring it to market. The research was funded by the Department of Energy.