Shape memory alloy microfilament yarns

Abstract

Shape memory yarns described herein include twisted microfilaments made from a shape memory alloy that may provide superelastic or shape memory properties. The shape memory yarns are formed into coils that provide a high degree of actuation or elasticity along an axis of the coiled shape memory yarn, and may have relatively low porosity, low rigidity, and/or low change of volume compared to shape memory coils formed from solid structures. Coiled shape memory yarns may provide further tailorability of a superelastic or shape memory response of a system or device incorporating the coiled shape memory yarns through various coil parameters, such as coil pitch or density, or torque balancing, such as heat treating or plying the coiled shape memory yarns.

1 : A shape memory coil comprising:
 a coiled shape memory yarn having a coil direction around a coil axis, wherein the coiled shape memory yarn comprises a plurality of microfilaments having a twist direction around a yarn axis, and   wherein the plurality of microfilaments comprises a shape memory alloy.   
     
     
         2 : The shape memory coil of  claim 1 , wherein the coil direction of the yarn and the twist direction of the plurality of microfilaments are different. 
     
     
         3 : The shape memory coil of  claim 1 , wherein the coil direction of the yarn and the twist direction of the plurality of microfilaments are the same. 
     
     
         4 : The shape memory coil of  claim 1 , wherein the plurality of microfilaments includes between about 10 and about 1000 microfilaments. 
     
     
         5 : The shape memory coil of  claim 1 , wherein the shape memory alloy comprises at least one of a nickel-titanium alloy or a copper-zinc-aluminum alloy. 
     
     
         6 : The shape memory coil of  claim 1 , wherein the plurality of microfilaments has an average diameter less than about 10 micrometers. 
     
     
         7 : A method for manufacturing a shape memory coil, comprising:
 coiling a shape memory yarn to form a coiled shape memory yarn that has a coil direction around a coil axis,   wherein the coiled shape memory yarn comprises a plurality of microfilaments having a twist direction around a yarn axis, and   wherein the plurality of microfilaments comprises a shape memory alloy.   
     
     
         8 : The method of  claim 7 , wherein the plurality of microfilaments has an average diameter less than about 10 micrometers. 
     
     
         9 : The method of  claim 7 , further comprising twisting the plurality of microfilaments to define the twist direction. 
     
     
         10 : The method of  claim 7 ,
 wherein the shape memory yarn is coiled around a mandrel to define the coil direction, and   wherein the coil direction of the yarn and the twist direction of the plurality of microfilaments are opposite.   
     
     
         11 : The method of  claim 10 , further comprising heat treating the yarn to torque balance the yarn. 
     
     
         12 : The method of  claim 7 ,
 wherein the yarn is coiled to create a torsional imbalance to define the coil direction, and   wherein the coil direction of the yarn and the twist direction of the plurality of microfilaments are the same.   
     
     
         13 : The method of  claim 12 , further comprising plying the shape memory yarn with one or more shape memory yarns to torque balance the shape memory yarn. 
     
     
         14 : A textile, comprising:
 a plurality of interlocked tows,   wherein at least a portion of the plurality of interlocked tows comprises a plurality of shape memory yarn structures,   wherein each shape memory yarn structure comprises one or more shape memory yarns,   wherein each shape memory yarn comprises a plurality of microfilaments having a twist direction around a yarn axis, and   wherein the plurality of microfilaments comprises a shape memory alloy.   
     
     
         15 : The textile of  claim 14 , wherein the plurality of microfilaments has an average diameter less than about 10 micrometers. 
     
     
         16 : The textile of  claim 14 , wherein the plurality of shape memory yarn structures comprises:
 a first plurality of shape memory yarn structures oriented in a first direction; and   a second plurality of shape memory yarn structures oriented in a second direction, different from the first direction.   
     
     
         17 : The textile of  claim 16 ,
 wherein the first plurality of shape memory yarn structures has a first elasticity, and   wherein the second plurality of shape memory yarn structures has a second elasticity, different from the first elasticity.   
     
     
         18 : The textile of  claim 16 ,
 wherein the first plurality of shape memory yarn structures is configured to produce a first actuation force in response to a transformation temperature transition, and   wherein the second plurality of shape memory yarn structures is configured to produce a second actuation force in response to a transformation temperature transition, different from the first actuation force.   
     
     
         19 : The textile of  claim 14 ,
 wherein the plurality of shape memory yarn structures defines a plurality of shape memory coils, and   wherein each shape memory yarn structure has a coil direction.   
     
     
         20 : The textile of  claim 14 , wherein each shape memory yarn structure comprises a plurality of yarns plied into the respective shape memory yarn structure. 
     
     
         21 : The textile of  claim 14 , wherein the plurality of shape memory yarn structures comprises at least one of woven tows or knitted loops. 
     
     
         22 : A system, comprising:
 one or more shape memory yarn structures, wherein each shape memory yarn structure comprises one or more shape memory yarns, wherein each shape memory yarn comprises a plurality of microfilaments having a twist direction around a yarn axis, wherein the plurality of microfilaments comprises a shape memory alloy, and wherein the shape memory alloy is configured to undergo a phase transformation in response to heating above a transformation temperature; and   a current source coupled to the one or more shape memory yarn structures, wherein the current source is configured to send an actuation signal to the one or more shape memory yarn structures to heat the one or more shape memory yarn structures above the transformation temperature of the shape memory alloy.   
     
     
         23 : The system of  claim 22 , wherein the plurality of microfilaments has an average diameter less than about 10 micrometers. 
     
     
         24 : The system of  claim 22 ,
 wherein the one or more of shape memory yarn structures defines one or more shape memory coils, and   wherein each shape memory yarn structure has a coil direction.