MadSci Network: Engineering

Re: What liquid, gel, or solution becomes solid when a current is applied?

Date: Wed Feb 22 01:45:28 2006
Posted By: Werner Sieber, Research Scientist,
Area of science: Engineering
ID: 1140466434.Eg

Hi Ricky,

The subject area of your question goes by the name of electro-rheology. There have been a number of articles and patents (e.g. US Pat. 4687589 (1987), BLOCK HERMANN; KELLY JEFFREY PHILIP) over the years, but as far as I know, none of the proposed systems has made it to the market. Electro-rheological fluids are dispersions of particles in a liquid (oil) of low electrical conductivity. If this dispersion is placed between two electrodes, and a high voltage is applied, the particles orient themselves in the electrical field and/or arrange themselves in chains. Both effects lead to a higher viscosity or yield points, i.e. higher resistance to deformation of the system. The main problem, as with many systems based on dispersions of solids, is the stability, and reproducibility, of the response as time goes by. In the beginning, a trace amount of water (adsorbed on the particles) seemed necessary for proper functioning. Later claims mentioned semiconductor particles etc. I have never seen a description of a system which turns completely and reversibly solid on application of a voltage.

Best Regards

Werner Sieber

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