Questions regarding Magnetorheological fluids

[dliu1004]

Hello, has anyone worked with magnetorheological fluids before?

I plan on creating one for a project by using carbonyl iron powder, a surfactant, and some oil. I have heard that when subject to a current, these liquids basically become solids. However, I am not sure if they become complete solids. How much more viscous, or how much more solid do these liquids become when subject to a current?

Also, just to confirm, the viscosity should increase as the current increases as well, right?

Thanks!

 

[berkeman]

Hello, has anyone worked with magnetorheological fluids before?

I plan on creating one for a project by using carbonyl iron powder, a surfactant, and some oil. I have heard that when subject to a current, these liquids basically become solids. However, I am not sure if they become complete solids. How much more viscous, or how much more solid do these liquids become when subject to a current?

Also, just to confirm, the viscosity should increase as the current increases as well, right?

Thanks!

I haven't used them before, but according to a couple articles that I found with a Google search, they respond to external magnetic fields, not to currents flowing through them. You would need to use something like a Helmholtz Coil or similar arrangement to generate a B-field through your material.

A magnetorheological fluid (MR fluid, or MRF) is a type of smart fluid in a carrier fluid, usually a type of oil. When subjected to a magnetic field, the fluid greatly increases its apparent viscosity, to the point of becoming a viscoelastic solid. Importantly, the yield stress of the fluid when in its active ("on") state can be controlled very accurately by varying the magnetic field intensity. The upshot is that the fluid's ability to transmit force can be controlled with an electromagnet, which gives rise to its many possible control-based applications. Extensive discussions of the physics and applications of MR fluids can be found in a recent book.[1]

MR fluid is different from a ferrofluid which has smaller particles. MR fluid particles are primarily on the micrometre-scale and are too dense for Brownian motion to keep them suspended (in the lower density carrier fluid). Ferrofluid particles are primarily nanoparticles that are suspended by Brownian motion and generally will not settle under normal conditions. As a result, these two fluids have very different applications.

https://en.wikipedia.org/wiki/Magnetorheological_fluid