Magnetorheological fluid compositions and prosthetic knees utilizing same

Abstract

The present invention relates in one embodiment to magnetorheological fluids utilized in prosthetic joints in general and, in particular, to magnetorheological fluids utilized in controllable braking systems for prosthetic knee joints. Preferred magnetorheological fluids of the present invention comprises polarizable iron particles, a carrier fluid, and optionally an additive. Preferred additives include, but are not limited to functionalized carrier fluids as well as derivatized fluoropolymers. Preferred carrier fluids include, but are not limited, to perfluorinated polyethers.

1 . A magnetorheological fluid comprising polarizable particles and a fluid component, 
 wherein the fluid component comprises a carrier fluid and an additive;    wherein the additive comprises a functionalized perfluorinated polyether fluid.    
     
     
         2 . The magnetorheological fluid of  claim 1 , wherein the functionalized perfluorinated polyether fluid comprises a monofunctionalized perfluorinated polyether fluid.  
     
     
         3 . The magnetorheological fluid of  claim 2 , wherein the monofunctionalized perfluorinated polyether fluid comprises a functional group selected from the group consisting of silane, phosphate, hydroxyl, carboxylic acid, alcohol, and amine.  
     
     
         4 . The magnetorheological fluid of  claim 1 , wherein the functionalized perfluorinated polyether fluid comprises a difunctionalized perfluorinated polyether fluid.  
     
     
         5 . The magnetorheological fluid of  claim 4 , wherein the difunctionalized perfluorinated polyether fluid comprises a functional group selected from the group consisting of dihydroxyl, ethoxy ether, isocyanate, aromatic, ester, and alcohol.  
     
     
         6 . The magnetorheological fluid of  claim 1 , wherein the polarizable particles comprise iron particles.  
     
     
         7 . The magnetorheological fluid of  claim 1  wherein the polarizable particles range in size from about 0.2 to about 50 microns.  
     
     
         8 . The magnetorheological fluid of  claim 7  wherein the polarizable particles range in size from about 0.4 to about 10 microns.  
     
     
         9 . The magnetorheological fluid of  claim 8  wherein the polarizable particles range in size from about 0.5 to about 9 microns.  
     
     
         10 . The magnetorheological fluid of  claim 1  wherein the polarizable particles comprise about 1 to about 60% (v/v) of the total magnetorheological fluid volume.  
     
     
         11 . The magnetorheological fluid of  claim 10  wherein the polarizable particles comprise about 10 to about 50% (v/v) of the total magnetorheological fluid volume.  
     
     
         12 . The magnetorheological fluid of  claim 11  wherein the polarizable particles comprise about 20 to about 40% (v/v) of the total magnetorheological fluid volume.  
     
     
         13 . The magnetorheological fluid of  claim 1  wherein the carrier fluid is selected from the group consisting of silicone, hydrocarbon, esters, ethers, fluorinated esters, fluorinated ethers, mineral oil, unsaturated hydrocarbons, and combinations thereof.  
     
     
         14 . The magnetorheological fluid of  claim 1  wherein the additive comprises from about 0.1 to about 20% (v/v) of the fluid component.  
     
     
         15 . The magnetorheological fluid of  claim 14  wherein the additive comprises from about 1 to about 15% (v/v) of the fluid component.  
     
     
         16 . The magnetorheological fluid of  claim 15  wherein the additive comprises from about 2 to about 10% (v/v) of the fluid component.  
     
     
         17 . The magnetorheological fluid of  claim 1  comprising: 
 about 28% (v/v) polarizable particles; and    about 72% (v/v) fluid component;    wherein said fluid component comprises about 5% (v/v) additive and about 95% (v/v) perfluorinated polyether carrier fluid.    
     
     
         18 . The magnetorheological fluid of  claim 1 , wherein the functionalized perfluorinated polyether fluid comprises a poly(hexafluoropropylene epoxide) with a carboxylic acid located on the terminal fluoromethylene group.  
     
     
         19 . A magnetorheological fluid comprising polarizable particles and a fluid component, 
 wherein the fluid component comprises a carrier fluid and an additive;    wherein the additive comprises a functionalized fluoropolymer.    
     
     
         20 . The magnetorheological fluid of  claim 19 , wherein the functionalized fluoropolymer comprises a parafluoropropene and oxygen polymerized amide derivative.