Method and apparatus for increasing and modulating the yield shear stress of electrorheological fluids
First Claim
1. A method for increasing the yield shear stress of an electrorheological fluid, the method comprising the steps of:
- a) applying a sufficient electric field to the electrorheological fluid to cause particles within the electrorheological fluid to form into chains of particles within the electric field; and
b) applying a sufficient pressure to the electrorheological fluid, after step a) and while substantially maintaining the electric field applied In step a), to cause the chains of particles to thicken or aggregate and Impart to the electrorheological fluid an increase in the yield shear stress;
wherein the electric field applied in step a) is in the range of about 250 V/mm to about 3000 V/mm and the pressure applied in step b) is in the range of about 50 kPa to about 850 kPa.
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Abstract
A method for increasing and/or modulating the yield shear stress of an electrorheological fluid includes applying a sufficient electric field to the fluid to cause the formation of chains of particles, and then applying a sufficient pressure to the fluid to cause thickening or aggregation of the chains. An apparatus for increasing and/or modulating the transfer or force or torque between two working structures includes an electrorheological fluid and electrodes through which an electric field is applied to the fluid such that particles chains of particles are formed in the fluid and, upon application of pressure to the fluid, the chains thicken or aggregate and improve the force or torque transmission.
34 Citations
10 Claims
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1. A method for increasing the yield shear stress of an electrorheological fluid, the method comprising the steps of:
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a) applying a sufficient electric field to the electrorheological fluid to cause particles within the electrorheological fluid to form into chains of particles within the electric field; and
b) applying a sufficient pressure to the electrorheological fluid, after step a) and while substantially maintaining the electric field applied In step a), to cause the chains of particles to thicken or aggregate and Impart to the electrorheological fluid an increase in the yield shear stress;
wherein the electric field applied in step a) is in the range of about 250 V/mm to about 3000 V/mm and the pressure applied in step b) is in the range of about 50 kPa to about 850 kPa. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
c) decreasing or increasing the applied pressure, after step b), to modulate the yield shear stress downwardly or upwardly, respectively;
ord) decreasing or increasing the applied electric field, after step b) to modulate the yield shear stress downwardly or upwardly, respectively;
ore) combining steps c) and d) to modulate the yield shear stress upwardly or downwardly as desired.
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7. The method according to claim 6, further comprising a step of removing at least one of the applied electric field and the applied pressure to produce a reduced yield shear stress.
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8. The method according to claim 7, wherein the applied electric field is removed to produce a yield shear stress of about 0.
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9. The method according to claim 1, wherein the electric field is about 1000 V/mm to about 3000 V/mm.
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10. The method according to claim 1, wherein the pressure applied is about 300 kPa to about 800 kPa.
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