You are an expert at summarizing long articles. Proceed to summarize the following text:

You are an expert at summarizing long articles. Proceed to summarize the following text: 
BACKGROUND OF THE INVENTION 
     Actuators in tubular systems, such as the downhole completion industry, employ a variety of motive devices. Electrical motors, solenoids, shape memory alloys and hydraulic systems, are a few of the motive devices successfully employed. Each motive device has specific advantages as well as drawbacks and each finds applications to which they are well suited. A wide variety of applications necessitate a wide variety of motive devices thereby assuring that operators of tubular systems remain receptive to new actuators employing new motive devices. 
     BRIEF DESCRIPTION OF THE INVENTION 
     Disclosed herein is an actuator that includes a tubular configured to longitudinally expand in response to radial expansion of at least a portion of the tubular. 
     Further disclosed herein is a tubular actuator that includes a sleeve and a tubular in operable communication with the sleeve configured to longitudinally expand in response to radial expansion thereof. A first portion of the tubular is longitudinally fixed to the sleeve so that a second portion of the tubular moves in relation to the sleeve in response to the longitudinal expansion of the tubular. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike: 
         FIG. 1  depicts a side view of an actuator disclosed herein in a nonactuated configuration; 
         FIG. 2  depicts a side view of the actuator of  FIG. 1  shown in an actuated configuration; 
         FIG. 3  depicts a perspective view of the actuator of  FIG. 1 ; 
         FIG. 4  depicts a perspective view of the actuator of  FIG. 2 ; 
         FIG. 5  depicts a partial cross sectional view of an alternate embodiment of an actuator disclosed herein in a nonactuated configuration; 
         FIG. 6  depicts a partial cross sectional view of the actuator of  FIG. 5  shown in an actuated configuration; 
         FIG. 7  depicts a partial cross sectional view of another alternate embodiment of an actuator disclose herein; and 
         FIG. 8  depicts a perspective view of a tubular actuator disclosed herein; 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures. 
     Referring to  FIGS. 1-4 , an embodiment of an actuator disclosed herein is illustrated at  10 . The actuator  10  includes, a tubular  14  with a discontinuous wall  18  having a plurality of serpentine or sinuous members  22  orientated substantially perimetrically about the tubular  14 . The serpentine members  22  have longitudinal amplitudes with a plurality of bars  26  connected thereto. Pairs of the bars  26  that are perimetrically adjacent to one another have opposingly directed ends  30 ,  34  connected to a same one of the serpentine members  22 . For example, the leftward end  30 , as illustrated herein, of one of the bars  26  is connected to a same one of the serpentine members  22  as the rightward end  34  of the perimetrically adjacent bar  26  such that the ends  30 ,  34  longitudinally overlap one another. The amount of overlap in this embodiment is by a dimension  38 . The decrease in dimension  38  in response to radial expansion of the actuator  10  is due to a decrease in amplitude of the serpentine member  22 . This decrease of overlap puts the bars  26  in compression that causes a longitudinal growth of the actuator  10 . This characteristic, longitudinal growth in response to radial growth is known as auxetic and is associated with the actuator  10  having a negative Poisson&#39;s ratio. 
     Straight portions  42  of the serpentine members  22  in this embodiment intersect the bars  26  at angles  46 . The angles  46  increase as the amplitude of the serpentine members  22  decreases thereby approaching 90 degrees. As the angles  46  increase, during actuation, the bars  26  transmit compressive loads. These compressive loads cause adjacent serpentine members  22  to move longitudinally away from one another. Making the tubular  14  of a strong material, such as metal, for example, facilitates efficient transmission of the compressive forces through the bars  26 . 
     Referring to  FIGS. 5 and 6 , an alternate embodiment of an actuator disclosed herein is illustrated at  110 . Unlike the tubular  14  of the actuator  10 , a tubular  114  of the actuator  110  has continuous walls. As such a wall  118  of the tubular  114  provides fluidic isolation between an inside  124  and an outside  128  of the tubular  118 . A wall  132  of the tubular  114  has a serpentine shape extending in a longitudinal orientation with amplitude  136  in a radial direction. When the actuator  110  is radially expanded inner points  140  of the tubular  114  are moved radially outwardly thereby putting portions  146  of the tubular  114  into compression which causes longitudinally adjacent inner points  140 , separated by dimension  150 , to move longitudinally away from one another resulting in longitudinal expansion of the actuator  110  as the dimension  150  increases in response to the radial expansion thereof. 
     Referring to  FIG. 7 , in an alternate embodiment of an actuator  210  disclosed herein, a tubular  214  has a serpentine shape with curved walls  218  as opposed to the straight walls  118  of the actuator  110 . Otherwise the actuator  210  is similar to the actuator  110  and functions substantially in the same manner. 
     Referring to  FIG. 8 , a tubular actuator  310  disclosed herein is illustrated in a perspective view. The tubular actuator  310  includes a sleeve  316  with the tubular  114 , positioned radially outwardly of the sleeve  316 . A first portion  324  of the tubular  114  is fixedly attached to the sleeve  316  near a first end  328  thereof while a second portion  332  of the tubular  114  near a second end  336  thereof is slidably engaged about the sleeve  316 . Both the tubular  114  and the sleeve  316  are radially expandable by operations such as swaging or pressurizing a fluid contained therewithin, for example. The sleeve  316  having a simply cylindrical shape has a positive Poisson&#39;s ratio and as such longitudinally contracts upon being radially expanded. In contrast, the tubular  114  has a negative Poisson&#39;s ratio, as discussed above and longitudinally expands upon being radially expanded. Assuming the first portion  324  of the tubular  114  and the sleeve  316  attached thereto are stationary, then the tubular actuator  310  will cause an actuatable movement of a portion  340  of the sleeve  316  relative to the second portion  332  of the tubular  114  upon radial expansion of both the sleeve  316  and the tubular  114 . This relative motion is generated by movement of the portion  340  of the sleeve  316  toward the first portion  324  while the second portion  332  moves away from the first portion  324 . A tool (not shown), by being connected to both the second portion  332  and the portion  340  of the sleeve  316 , can be actuated through radial expansion of the tubular actuator  310 . It should be noted that although this embodiment discloses the sleeve  316  having a positive Poisson&#39;s ratio, other embodiments are contemplated that have non-positive Poisson&#39;s ratios. In fact, as long as the Poisson&#39;s ratios of the sleeve  316  and the tubular  114  are not the same the tubular actuator  310  will provide relative movement between the portion  340  and the second portion  332  enabling actuation thereby. 
     Embodiments of the actuators  10 ,  110 ,  210  and the tubular actuator  310  disclosed herein can be used in various industries. In the downhole completion industry, for example, the actuators  10 ,  110 ,  210 ,  310  could be used to actuate the following tools; a packer, a centralizer, a backup, an anchor, a valve and a crusher (none shown). 
     While the invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims.

Summary:
An actuator includes a tubular configured to longitudinally expand in response to radial expansion of at least a portion of the tubular.