Electrorheological(ER) Fluids An electrorheological fluid changes its apparent viscosity in the presence of an electric field. As seen in the video, the green liquid is runny and its viscosity is low when there is no electric field. But when an electric field is applied, it increases in viscosity greatly and is holds itself between the two electrodes.
Electrorheoligical fluids are colloidal suspensions of particles of whose properties depend strongly on the presence of an electric field. When these fluids have an electric field applied to them they form a fibrous structure parallel to the to the applied field as seen in the diagram below.. |
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This fibrous structure is caused by the fluid being a non-conducting liquid and the particles being more conductive than the fluid. The electric field aligns the conducting particles to create a path for the current pass through the liquid. The ER effect will only take place if the thermal brownian forces are less than the dipolar forces of the electric field, as the particles will not be able to align and the viscosity will not be altered.
Electrorheological fluids have many engineering applications. In fast acting hydraulic valves,clutches,shock absorbers they are widely used. The ER effect also occurs naturally in substance such as potatoto starch and milk chocolate In Natural ER fluids there is still an insulating fluid with more conductive particles in a colloidal suspension. In milk chocolates case it is thought that the fat proteins are the are the polarising particles.
If Synovial fluid is an ER fluid it will most likely not operate in the same way as these ER fluids. Synovial fluid is a conducting fluid so the polarisation of particulates inside it is unlikely. It is although possible as conductive is a relative term. If there are particulates which are highly conductive in comparison to the fluid this effect might still occur. It would be more likely that a different ER operator would be causing a change in viscosity. Possibilities for causing the ER effect could be piezoelectric stresses causing non-newtonian responses from fluid fluid or biological responses from cells within the fluid. Further research will need to be done to present founded theories.
Electrorheological fluids have many engineering applications. In fast acting hydraulic valves,clutches,shock absorbers they are widely used. The ER effect also occurs naturally in substance such as potatoto starch and milk chocolate In Natural ER fluids there is still an insulating fluid with more conductive particles in a colloidal suspension. In milk chocolates case it is thought that the fat proteins are the are the polarising particles.
If Synovial fluid is an ER fluid it will most likely not operate in the same way as these ER fluids. Synovial fluid is a conducting fluid so the polarisation of particulates inside it is unlikely. It is although possible as conductive is a relative term. If there are particulates which are highly conductive in comparison to the fluid this effect might still occur. It would be more likely that a different ER operator would be causing a change in viscosity. Possibilities for causing the ER effect could be piezoelectric stresses causing non-newtonian responses from fluid fluid or biological responses from cells within the fluid. Further research will need to be done to present founded theories.