a neutral displacement wick ( ndw ) in accordance with some embodiments of the present invention will now be discussed . the advantage of a ndw wick when used in air freshener devices or similar applications is that when the wick is first introduced into the fluid reservoir , it may absorb a desired amount of liquid into the wick relative to the amount it displaces , resulting in the liquid level in the fluid reservoir remaining at or near the level present before the wick was introduced , or at some other desired level . if the wick is capped off or otherwise enclosed to prevent evaporation , the device may be shipped to the consumer who may then have the perception that he or she is buying a full container . when the cap is removed , the large surface area of the wick sheath may allow dissemination of fragrance . with reference to fig1 , a multi - component ndw wick 10 may comprise at least four ( 4 ) non - discrete ( i . e ., overlapping ) portions : an immersion section 110 , an non - immersion section 120 , a displacement portion 130 , and a wicking portion 140 . the immersion section 110 and the non - immersion section 120 divide the wick laterally , while the displacement portion 130 and wicking portion 140 provide radial divisions in the wick 10 . the immersion section 110 is the section of the multi - component wick that is initially in the fluid . the non - immersion section 120 is the section of the multi - component wick that is initially outside of the fluid . the displacement portion 130 may run the entire length of the wick , or may be primarily disposed in the immersion section 110 . while the displacement portion 130 may possess some wicking characteristics , its primary purpose is to initially displace a specified amount of fluid . the wicking portion 140 may also run the entire length of the wick , although it is also contemplated to have the majority of the wicking portion 140 in the non - immersion section 120 of the wick . the surface area of the wicking portion 140 in the non - immersion section 120 will determine the dissemination rate of the evaporated fluid . with reference to fig2 - 5 , various cross - sections of a ndw will now be discussed . in fig2 , a ndw 20 may be configured in a cylindrical shape , and may comprise a displacement portion 210 and a wicking portion 220 . the displacement portion 210 is shown as being radially - internal to the wicking portion 220 . in this manner , the displacement portion 210 may not only be generally hidden , but the wicking portion 220 may be fully exposed to the ambient environment , thereby allowing for optimal evaporation , and thus , fragrance dissemination . in fig3 , a ndw 30 may again be comprised in a cylindrical shape and may comprise a first wicking portion 310 , and a second wicking portion 320 . the ndw 30 may also comprise an impervious membrane 340 and a void area 350 . it is contemplated that the void area 350 may be used similar to the displacement portion in fig1 and 2 to displace a desired amount of fluid . the first wicking portion 310 may be designed to wick a specific material ( e . g ., it may be hydrophilic ) while the second wicking portion 320 may be designed to wick a different specific material ( e . g ., it may be oleophilic ), providing for multiple scents emitting from the ndw 30 . additionally , the first and second wicking portions 310 , 320 may wick the same materials at different rates , or either the first or the second wicking portion 310 , 320 may have aromas embedded therein . in fig4 , a ndw 40 may be rectangular in cross - section , and may comprise a displacement portion 410 and a wicking portion 420 . similarly , in fig5 , a ndw 50 may comprise at least three ( 3 ) portions : a first wicking portion 510 , a second wicking portion 520 , and a displacement portion 530 . alternatively , the ndw 50 may comprise a wicking portion and a displacement portion separated by an impervious membrane . other example cross sections may be a wicking core and a non - wicking sheath , or any other configurations that would be obvious to one skilled in the art . many materials may be used in the wicking portion of the ndw wick . such materials may be self - sustaining porous bonded fiber elements that are well known to be able to be engineered to wick a variety of liquids and act as air freshener wick materials . examples of such materials may include bonded bicomponent polyolefin sheath fibers , bonded bicomponent polyester sheath fibers , bonded bicomponent nylon sheath fibers and bonded pneumatic nylon and pneumatic cellulose acetate . other examples of materials that may be suitable for use in the wicking portion of the ndw wick may include porous , non - bonded , wicking fiber elements , which may be stiffened by adhesives or otherwise made structurally sound to enable consistent wicking behavior . woven , knitted or non - woven fabrics may be used , as well as natural fibrous or non - fibrous products ( such as cotton or wool ). in addition , open cell foams may be used ( as long as they are of sufficient surface energy to allow wetting and wicking of the target fluid ). additionally , porous plastics , such as self - sustaining porous sintered plastic elements , may be used . various other materials that provide adequate wicking and evaporation will be readily apparent to one skilled in the art . in general , the non - wicking portion may be any material as long as it is so configured so that the target fluid will substantially not penetrate this portion and thus be displaced by the non - wicking portion . the non - wicking portion of the ndw wick may be impervious , and may be a closed cell foam material , such as a rod - shaped chemically resistant polyethylene or polyurethane foam , a solid rod , such as a variety of plastic or elastomeric rods , or even rods of wood or metal . the non - wicking portion may also be bonded or non - bonded fiber structures , or natural product structures , with the surface energy being such that the material would not wet out or wick the target fluid , even under elevated pressure conditions that may be experienced in a container . the wicking portion may be tight up against the non - wicking displacement portion to prevent voids from forming . unsealed voids are unwanted because upon filling with the fragrant liquid , the volume of the container may appear to be less . the wicking portion and the non - wicking displacement portion may be arranged so as to prevent unwanted delamination or separation of the two portions . for example , the wicking portion and the non - wicking displacement portion may be combined into a single unit by interference fit , or may be adhered together . such adherence may be the result of fibers of the wicking portion bonding to the non - wicking displacement portion , or may result from the use of adhesives applied to the components . in general , the wick may be sized to achieve the following objectives : 1 . the proper surface area ( as determined by the circumference of the wick , the amount of wick exposed in the non - immersion section , and the vapor pressure of the target fluid ). a proper surface area may allow a vapor release rate appropriate to the application in question . 2 . appropriate volume of liquid wicked up into the wick by capillary action ( determined by the cross sectional area of the wicking portion , plus the capillary draw and porosity of the porous element ). 3 . the amount of liquid displaced ( determined by ( 2 ) above plus the displacement of the displacement portion ). 4 . a desired relationship between the immersion section and the non - immersion section . for example , in some circumstances , it may be desirable to maintain a fluid level at the same height once a wick is inserted . in this situation , the initial volume of the immersion section ( comprising the volume of both the displacement portion and the fiber volume of the wicking portion ) should be approximately equal to the initial volume of fluid wicked by the wicking portion located in the non - immersion section . in other circumstances , it may be desirable to cause the fluid level to rise or drop once a wick is inserted . in such circumstances , the volume of the immersion section may initially be more or less , respectively , than the volume of fluid initially wicked by the wicking portion in the non - immersion section . the need for proper sizing of the ndw wick may be apparent from fig6 - 10 . in accordance with some embodiments of the present invention , fig6 - 10 illustrate the proper sizing for a ndw where the immersion section displaces an amount of fluid approximately equal to the amount fluid wicked into the wicking portion of the non - immersion section ( note that the fluid level remains the same throughout ). fig6 and 7 illustrate the undesirable effect of initial liquid drop in a fluid reservoir when a standard , non - ndw wick is used . it is desirable to properly size or configure an ndw wick to prevent similar fluid drops . fig8 - 9 illustrate a properly sized ndw wick that displaces an equal amount of liquid as it initially absorbs , maintaining the initial fluid level at approximately the top of the bottle . fig1 illustrates an improperly sized wick that displaces more fluid than it absorbs , resulting in fluid overflow upon insertion . the ratio of the volume of liquid displaced by the immersion section ( including the displacement portion ) to the volume of liquid initially wicked into the wicking portion in the non - immersion section must be designed for each particular application , and must take into account the volume of the container , the size of the ndw and the desired liquid height inside the container before and after the insertion of the ndw . ratios may range from 0 . 2 to 4 . 0 . when a particular fluid level prior to ndw insertion is desired to be maintained after ndw insertion , ratios may range from 0 . 95 to 1 . 05 . design considerations include , but are not limited to , the desired evaporation rate of the liquid , the surface tension of the liquid that is to be wicked , the density of the wicking portion , the overall dimensions of the wicking portion , and the overall dimensions of the container . ndw may also be made in many different ways , including bonded fiber processes of many types , non - woven wrapping technologies , textile technologies , and a variety of forming technologies . ndw may be produced by separately manufacturing the porous , wicking portion and the non - wicking portion , and combining the portions into a final unit . as noted above , this combination may utilize an interference fit , may be thermally bonded together as part of the forming process or may utilize additional adhesives . alternatively , the wicking portion may be formed integral to the displacement portion . for example , in arrangements such as those depicted in fig2 , and 3 wherein the wicking portion surrounds the displacement portion the wicking portion may be formed around and integral to , the displacement portion , or , in the case of fig3 , around a sealed void that provides the desired displacement . with reference to fig1 , one manner of producing ndw in accordance with some embodiments of the present invention will now be discussed . the displacement portion 1110 may be already formed . the displacement portion 1110 may comprise any material that does not wick or wet out with the intended liquid . for example , the displacement portion 1110 may be a solid , a closed cell foam such as a chemically resistant polyethylene or polyurethane foam . although the geographic arrangement of the displacement portion 1110 is illustrated in fig1 as being cylindrical , it may take any desired cross - section . the wicking portion 1120 may be formed from a fibrous sheet into a three dimensional , self - sustaining structure around the displacement portion 1110 . sheets or webs of fibrous material 1120 may be fed around the displacement portion 1110 to wrap or encase it . the encased combination of the fibrous material 1120 and the displacement portion 1110 may be fed into a heated die 1130 . the die 1130 may be heated by any variety of means ( e . g ., steam , induction , convection , etc .) and may maintain a temperature above the softening temperature of the fibers of the wicking portion 1120 . if the wicking portion 1120 is comprised of bicomponent fibers ( e . g ., sheath - core or side - by - side bicomponent fibers ) the die 1130 may be maintained at a temperature above the softening temperature of the lowest softening ( or melting ) temperature component . if sheath - core bicomponent fibers are used , the softening temperature of the sheath will be exceeded by the temperature of the die 1130 . the heat from the die 1130 may cause the fibers to bond to each other at various points of contact . upon cooling , the wicking portion may be formed into the desired three dimensional , self - sustaining , porous fiber structure . the inner dimensions of the die may form the combined wicking portion 1120 and displacement portion 1110 into a desired cross section . optionally , a cooling die 1140 may be used to quicken the cooling of the heated fibers . additionally , the cooling die 1140 may provide additional shaping of the cross section of the final product . upon exit from the heating die 1130 and optionally the cooling die 1140 , the ndw 1170 is formed . the combined ndw 1170 may be pulled through the process by element 1160 , and may be cut to desired length by element 1150 . although fig1 depicts an ndw 1170 in a cylindrical shape with a circular cross section of both the wicking portion and the displacement portion , it is anticipated that any desired cross section may be obtained . as noted above , fig1 illustrates a single method for the manufacture of a ndw . multiple other manufacturing methods may be used to produce , either separately or integrally , the wicking portion and displacement portion of the ndw . it will be apparent to those skilled in the art that various modifications and variations can be made in the method , manufacture , configuration , and / or use of the present invention without departing from the scope or spirit of the invention .