I first heard about Electrorheological (ER) fluids back in 1999 or 2000. Back then, I just thought it was an awesome idea! And indeed it is an awesome idea. But what are Electrorheological fluids after all? Here’s an excerpt from Wikipedia’s entry on this topic:
Electrorheological (ER) fluids are suspensions of extremely fine electrically active particles (up to 50 micrometres diameter) in a non-conducting fluid. The apparent viscosity of these fluids changes reversibly by an order of 100,000 in response to an electric field. For example, a typical ER fluid can go from the consistency of a liquid to that of a gel, and back, with response times on the order of milliseconds. The effect is sometimes called the Winslow effect, after its discoverer the American inventor Willis Winslow, who obtained a US patent on the effect in 1947 and wrote an article published in 1949.
The normal application of ER fuids is in fast acting hydraulic valves and clutches, with the separation between plates being of the order of 1 mm and the applied potential being of the order of 1 kV. In simple terms, when the electric field is applied, an ER hydraulic valve is shut or the plates of an ER clutch are locked together, when the electric field is removed the ER hydraulic valve is open or the clutch plates are disengaged. Other proposed uses are ER brakes or shock absorbers.
ER fluids should allow one to build really cool electro-mechanical actuators. Does anyone out there have any knowledge/experience on this? I would be happy to learn more, so feel free to comment and share your thoughts! If you fancy this topic, yet another kind of smart fluids are the Magnetorheological fluids.
This post is motivated by an “idea” I had some months ago: to use ER fluids for “controlled damping” (I have just made up this term) of mechanical oscillators. Possible applications: car suspensions, of course, among many others. Too bad I am a few decades late (as usual), since many people seem to have thought about that already.
Some links to satisfy your curiosity: