Patent Publication Number: US-2020276429-A1

Title: Tattoo needle tip with a capillary ink reservoir and combined device thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part application of U.S. patent application Ser. No. 15/123,464, filed Sep. 2, 2016, entitled “Tattoo Needle Tip with a Capillary Ink Reservoir and Combined Device Thereof”, which is a national stage application of PCT International Application No. PCT/CN2015/075980, which is filed Apr. 7, 2015 and claims the benefit of, and priority from, Chinese Invention Patent Application No. 201420167938.8, filed Apr. 8, 2014, the entire contents of each of which are incorporated herein by reference. 
     This application is also a continuation-in-part and, claims the benefit of, and priority from, U.S. patent application Ser. No. 15/874,597, filed Jan. 18, 2018, the entire contents of which are incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure relates to an application device for tattooing or for making permanent make-up, particularly relates to a tattoo needle tip with a capillary ink reservoir and its combined devices with a handle and with a tattoo needle, and devices for applying a liquid to skin, particularly to disposable needle assemblies utilizing capillary action for feeding ink or another liquid in such devices. 
     BACKGROUND 
     A conventional tattoo device generally includes a tattoo machine, a handle, a needle tip and a tattoo needle. The user assembles these components together before use. While assembling, the handle is connected to the tattoo machine, the needle tip is placed on the handle, the tattoo needle passes through the central hole of the handle with the sharp end of the needle thereof reaching the opening of the tattoo needle tip. 
     In prior art, the basic shape of the needle tip is essentially a cylindrical tube. One end of the needle tip has a frustum section with a needle passage being defined therethrough. The free end of the frustum section is provided with a needle opening for the tattoo needle extending out. 
     The interior of the frustum section of the needle tip forms an inner cavity in a shape of a frustum. The inner cavity is communicated with the needle opening. The inner walls of the inner cavity and the needle opening are mostly designed to be streamlined and smooth, so as to prevent the sharp end of the needle from resisting when the tattoo needle is inserted thereby preventing the sharp end of the needle from bending. Meanwhile the inner cavity also serves as an ink reservoir. 
     During operation, the tattoo needle is doing a straight-line reciprocating motion in high frequency. The sharp end of the needle wetted by tattoo ink rushes out from the needle opening and stabs into the skin, then the sharp end of the needle returns into the needle opening for dipping some ink and then rushes out again. The section of the needle opening for feeding ink to the sharp end of the needle is the feed section. When adding ink to the needle tip, the tattooist inserts the needle tip into a small ink cup. There is a gap between the inner wall of the needle opening and the tattoo needle. Generally the ink will go into the needle opening and moisturize the needle opening and the inner wall of the needle passage. Some tattooists will briefly start the tattoo machine at the same time as dipping ink, then the tattoo needle does an up and down reciprocating motion in high speed, which will raise the ink to fill the inner cavity of the frustum section. In tattooing, the smooth inner wall of the inner cavity in the needle tip cannot effectively retain the ink. Therefore, the ink will flow to the needle opening due to the gravity and the motion of the tattoo needle. 
     The common issue met by tattooists when using these needle tips is that, if too much ink is added to the needle tip, it is easy to cause leakage of ink and pollute the tattoo during tattooing. In order to avoid the leakage of ink, tattooists have to add little ink each time, which increases the frequency of adding ink and results in ink failure or insufficient ink provision. However, it is inconvenient for tattooists to add ink frequently in tattooing. The frequent occurrence of ink failure or insufficient ink provision will adversely affect tattooists in drawing fluent and long tattoo lines. 
     U.S. Patent No. 20130226211 A1 and Chinese patent No. 202538157U disclose a needle tip with a capillary ink reservoir. The ink reservoir has functions of ink storage and ink maintenance, whereby once dipping ink, the tattoo needle tip can keep tattooing for a longer time. Thus, tattooists can avoid dipping ink frequently when tattooing. The capillary ink reservoir is connected to the needle opening via an ink guide channel. There is a certain distance from the capillary ink reservoir to the needle opening. To quickly fill the capillary ink reservoir with ink, tattooists need to immerse the ink reservoir in the small ink cup with a deeper insertion when dipping ink. Since the deeper insertion leads to too much ink on the outside surface of the needle tip, tattooists have to constantly wipe off the ink on the outside surface of the needle tip. Due to the ink guide channel spaced between the ink reservoir and the needle opening, it is not easy to supply ink with poor mobility and high viscosity to the needle opening timely and sufficiently. There is a phenomenon that some amount of ink left in the capillary ink reservoir cannot flow to the needle opening, which results in the low efficiency of the capillary ink reservoir. The ink guide channel cannot adapt well to ink of different viscosities at the same time. For ink of low viscosity, a gap size of the ink guide channel shall be smaller, which will cause ink of high viscosity from failing to flow through the channel fluently. Thus, the gap size of the ink guide channel should be bigger for ink of high viscosity, which will cause flooding or leakage of ink of low viscosity. 
     For safety reasons, the needle is typically sterilized before use and replaced after each use. It is thus convenient to use replaceable and disposable needle modules or needle tips, which can be pre-sterilized and easily detached or connected to the needle handle so that the needle can be easily replaced, and safely disposed. Disposable needle modules, particularly single-use disposable needle modules or similar disposable needle assemblies are thus often used with tattooing devices and other similar devices. Devices or applicators for applying permanent mark-up may have a similar construction, with a base, a replaceable handle, and a replaceable/disposable needle module. There are a number of drawbacks in existing disposable needle assemblies. 
     SUMMARY 
     An aspect of the present disclosure relates to solving one or more problems present in the existing ink feeding techniques used for feeding ink in a tattooing device. 
     It is desirable to provide a tattoo needle tip with a capillary ink reservoir, which has functions of ink storage and ink maintenance, does not easily cause leakage of ink, and insures rapid filling of the ink reservoir, also insures effective feeding of the ink to the sharp end of the tattoo needle during tattooing. 
     It is also desirable to provide a combined device comprising a tattoo needle tip with a capillary ink reservoir and a handle, which forms a combined component of a tattoo device, has functions of ink storage and ink maintenance, does not easily cause leakage of ink, and insures rapid filling of the reservoir, also insures effective feeding of the ink to the sharp end of the tattoo needle during tattooing. 
     It is further desirable to provide a combined device comprising a tattoo needle tip with a capillary ink reservoir and a tattoo needle, which forms a combined component of a tattoo device, has functions of ink storage and ink maintenance, does not easily cause leakage of ink, and insures rapid filling of the reservoir, also insures effective feeding of the ink to the sharp end of the tattoo needle during tattooing. 
     In an embodiment of the present disclosure, a tattoo needle tip with a capillary ink reservoir of the present disclosure includes a needle tip body. A needle passage is defined inside the needle tip body for placing a tattoo needle. A needle opening is defined at one end of the needle tip body for the sharp end of the tattoo needle to extend out. The needle opening is communicated with the needle passage. A capillary ink reservoir adapted to receive and retain ink therein by capillary action is disposed on the needle tip body and directly connected to the needle opening whereby the ink reservoir can directly feed ink to the sharp end of the tattoo needle. A plurality of capillary ink containing bodies may be provided at the ink reservoir and be directly connected to the needle opening. Each ink containing body may be a capillary aperture defined in the ink reservoir. All the capillary apertures defined in the ink reservoir may be connected to the needle opening directly. The ink reservoir may be made of porous material or fibrous material, and the ink containing bodies may include pores in the ink reservoir or gaps between fibers. The ink reservoir may be integrally or detachably formed at the needle tip body. 
     In another embodiment, a combined device includes a handle and a tattoo needle tip with a capillary ink reservoir installed to the handle. The tattoo needle tip includes a needle tip body. A needle passage is defined inside the needle tip body for placing a tattoo needle. A needle opening is defined at one end of the needle tip body for the sharp end of the tattoo needle to extend out. The needle opening is communicated with the needle passage. A capillary ink reservoir adapted to receive and retain ink therein by capillary action is disposed on the needle tip body and directly connected to the needle opening whereby the ink reservoir can directly feed ink to the sharp end of the needle. 
     A combined device in accordance with a further embodiment includes a tattoo needle tip with a capillary ink reservoir and a tattoo needle installed therein. The tattoo needle tip includes a needle tip body. A needle passage is defined inside the needle tip body for placing the tattoo needle. A needle opening is defined at one end of the needle tip body for the sharp end of the tattoo needle to extend out. The needle opening is communicated with the needle passage. A capillary ink reservoir adapted to receive and retain ink therein by capillary action is disposed on the needle tip body and directly connected to the needle opening whereby the ink reservoir can directly feed ink to the sharp end of the needle. A plurality of capillary ink containing bodies may be provided at the ink reservoir and be directly connected to the needle opening. Each ink containing body may be a capillary aperture defined in the ink reservoir. All the capillary apertures defined in the ink reservoir may be connected to the needle opening directly. The ink reservoir may be made of porous material or fibrous material, and the ink containing bodies may include pores in the ink reservoir or gaps between fibers. The ink reservoir may be integrally or detachably formed at the needle tip body. 
     By locating the ink reservoir at the needle tip, the capillary principle is utilized to store ink in the ink reservoir, which can store and retain a great amount of ink. Therefore, the leakage of ink does not easily happen. The ink containing body of the ink reservoir is connected to the needle opening directly, and the sharp end of the needle continuously dips the ink in the needle opening via the reciprocating motion of the tattoo needle, realizing that dipping and adding ink once, the tattoo needle tip keeps tattooing for a longer time, so as to avoid dipping and adding ink frequently when tattooists are tattooing. Moreover, it is quick and easy to dip and add ink to the ink reservoir. 
     In an aspect, there is provided a tattoo needle tip comprising a needle tip body having a lower end and an upper end; a needle passage defined inside the needle tip body for placing a tattoo needle; a needle opening defined at the lower end of the needle tip body for a sharp end of the tattoo needle to extend out, the needle opening being communicated with the needle passage; a capillary ink reservoir receiving and retaining ink therein by capillary action being disposed on the needle tip body and directly connected to the needle opening, the ink reservoir directly feeding ink to the sharp end of the tattoo needle, wherein a plurality of capillary ink containing bodies are provided at the ink reservoir and are directly connected to the needle opening. 
     Further, it has been recognized that in some cases, even when there is still some or a substantial amount of ink in the ink reservoir, little or no ink is supplied to the needle nozzle opening or the sharp end of the needle. More efficient utilization of the ink in the ink reservoir is desirable. Further, residual ink left in the ink reservoir also makes it difficult to clean the ink reservoir and switch ink color during use. It has been surprisingly discovered that ink feeding by capillary action may be improved by increasing direct contact between the needle and the ink in the ink reservoir or the capillary ink feeding channel. Test results have shown that a larger contact area between the needle and ink in the ink reservoir provides better feeding performance. Lack or limited contact between the needle and the ink in the ink reservoir or feeding channel causes inconsistent ink flow and excessive residual ink. 
     Thus, in a further aspect of the present disclosure, a needle assembly comprises a tattoo needle tip described herein and a tattoo needle mounted in the needle passage of the tattoo needle tip. In this needle assembly, the needle passage comprises a tubular longitudinal channel extending between the lower end and the upper end of the needle tip body, and a guide surface adjacent to the needle opening at the lower end of the needle tip body; the capillary ink containing bodies comprise a plurality of grooves extending generally transversely in the guide surface; a biasing member configured to bias the tattoo needle towards the guide surface across the grooves such that, during longitudinal reciprocal movement of the sharp end of the tattoo needle through the needle opening, contact or a capillary gap between the sharp end of the tattoo needle and the guide surface is maintained to continuously draw ink out of the grooves by capillary action. The needle assembly may be provided in the form of a needle module or a needle cartridge. 
     There is also disclosed a needle assembly for a liquid applicator such as an ink applicator. The needle assembly includes a housing comprising a tubular longitudinal channel and a guide surface. The channel has an upper open end and a lower open end. A plurality of liquid storage grooves for storing liquid therein by capillary action extend generally transversely in the guide surface above the lower open end. A needle bundle is mounted in the housing. The needle bundle includes one or more needles longitudinally reciprocally movable in the channel and is biased against the guide surface across the grooves such that, during longitudinal reciprocal movement of the needle bundle, the needle bundle maintains contact with the guide surface and the liquid stored in the grooves for drawing the liquid out of the grooves by capillary action. The liquid may include ink. 
     Conveniently, the contact between the needle bundle and the liquid in the liquid storage grooves can be consistently maintained by the biasing force to provide stable and efficient liquid feeding. 
     The needle assembly may comprise a biasing member configured to bias the needle bundle to move longitudinally and against the guide surface. The biasing member may comprise a resilient band. The biasing member may comprise a silicone, latex, or rubber material. The guide surface may be shaped to conform to an external profile of the needle bundle to increase contact area between the needle bundle and the liquid stored in the grooves. The needle assembly may comprise a plurality of needles welded or soldered to one another. The needle bundle may comprise 1 to 27 needles. The housing may comprise a generally cylindrical or conical body having a circumference, and one or more of the grooves may extend up to 120° along the circumference of the body. The longitudinal channel may have a generally circular profile, or a generally polygonal profile. The grooves may have a width of about 0.3 mm to about 0.6 mm. The plurality of grooves may comprise 3 to 12 grooves. The housing may comprise a generally conical lower portion and a generally cylindrical upper portion. The grooves may be separated from one another. The grooves may be inter-connected. The housing may comprise an observation window opposite the guide surface, and the needle bundle may comprise a shaft portion and a needle tip portion (needle head), where the shaft portion has a first longitudinal axis and the needle tip portion (needle head) has a second longitudinal axis, which is offset from the first axis towards the observation window. 
     In another aspect, there is provided a needle assembly for a liquid applicator, comprising a housing comprising a tubular longitudinal channel and an inner surface, the channel comprising an upper open end and a lower open end, a plurality of liquid storage grooves for storing liquid therein by capillary action extending generally transversely in the inner surface above the lower open end; a needle bundle mounted in the housing, the needle bundle comprising one or more needles longitudinally reciprocally movable in the longitudinal channel and being biased towards the inner surface across the grooves to form a capillary gap between the needle bundle and the inner surface for drawing liquid out of the liquid storage grooves during longitudinal reciprocal movement of the needle bundle across the grooves. 
     In a further aspect, there is provided a liquid applicator such as an ink applicator, which comprises a needle assembly disclosed herein. The liquid applicator may comprise a needle actuator for actuating downward movement of the needle bundle, and a handle coupling the needle actuator to the needle assembly. The liquid applicator may comprise a tattooing device. 
     Other aspects, features, and embodiments of the present disclosure will become apparent to those of ordinary skill in the art upon review of the following description of specific embodiments in conjunction with the accompanying figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the figures, which illustrate, by way of example only, embodiments of the present disclosure: 
         FIG. 1  is a perspective view of a tattoo needle tip with a capillary ink reservoir according to one embodiment of the present disclosure; 
         FIG. 2  is a partial section view of  FIG. 1 ; 
         FIG. 3  is a perspective view of a combined device including a tattoo needle tip with a capillary ink reservoir and a handle according to one embodiment of the present disclosure; 
         FIG. 4  is a perspective view of a combined device including a tattoo needle tip with a capillary ink reservoir and a handle according to another embodiment of the present disclosure; 
         FIG. 5  is a partial section view of  FIG. 4 ; 
         FIG. 6  is a perspective view of a combined device including a tattoo needle tip with a capillary ink reservoir and a handle according to a further embodiment of the present disclosure; 
         FIG. 7  is a perspective view of a combined device including a tattoo needle tip with a capillary ink reservoir and a tattoo needle according to one embodiment of the present disclosure; 
         FIG. 8  is a partial section view of  FIG. 7 ; 
         FIG. 9  is a perspective view of a combined device including a tattoo needle tip with a capillary ink reservoir, a handle, a tattoo needle and a tattoo machine according to the present disclosure; 
         FIG. 10A  is a right side view of the partially-cut device of  FIG. 7 , with the partial section view cut along the axial central line and with the needle being centrally positioned; 
         FIG. 10B  is a front elevation view of the device of  FIG. 10A ; 
         FIG. 10C  is the same view as in  FIG. 10A , except the needle being biased downward towards the inner surface of the needle passage; 
         FIG. 10D  is a front elevation view of the needle tip of  FIG. 10C ; 
         FIG. 11  is a front elevation view of a disposable needle module, illustrative of another embodiment of the present disclosure; 
         FIG. 12  is an exploded perspective view of the needle module of  FIG. 11 ; 
         FIG. 13A  is a side cross-sectional view of the needle module of  FIG. 11 ; 
         FIG. 13B  is a side elevation view of certain parts of the needle module shown in  FIG. 13A ; 
         FIG. 13C  is a force diagram showing the force applied to the needle bundle shown in  FIG. 13B ; 
         FIG. 14A  is a partially-cut perspective view of the needle module of  FIG. 11 ; 
         FIG. 14B  is an axial cross-sectional view of the needle module of  FIG. 14A , taken along line  14 B- 14 B in  FIG. 14A ; 
         FIG. 14C  is an enlarged view of the portion  14 C of the needle module of  FIG. 14A ; 
         FIG. 14D  is an enlarged view of the portion  14 D of the needle module of  FIG. 14B ; 
         FIGS. 15A, 15B, 15C, 15D and 15E  are axial cross-sectional views of various variants of the needle module, illustrative different embodiments of the present disclosure; 
         FIG. 16  is a side elevation view of a tattooing device, with partial cut-away cross-sectional view of the needle handle and needle module in the tattooing device, illustrative embodiments of the present disclosure; 
         FIGS. 17A and 17B  are exploded and perspective views of the needle in the needle module of  FIGS. 11 and 12 , respectively, illustrating the assembly of the needle; 
         FIGS. 18A and 18B  are perspective views of the cap in the needle module of  FIGS. 11 and 12 ; 
         FIG. 19A  is a perspective view of another needle module, according to an embodiment of the present disclosure; 
         FIG. 19B  is a side elevation view of the needle module of  FIG. 19A ; 
         FIG. 19C  is an enlarged cross-sectional view taken along the line  19 C- 19 C of  FIG. 19A . 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present disclosure relate to tattoo devices and needle assemblies as illustrated in  FIGS. 1 to 19C . 
     As shown in  FIGS. 1-2 , a tattoo needle tip  10  with a capillary ink reservoir according to one embodiment of the present disclosure includes a needle tip body  11 . A needle passage  100  is provided through the needle tip body  11  for placing a tattoo needle  20  (see  FIG. 7 ). As depicted, the needle passage includes a tubular longitudinal channel extending between a lower end and an upper end of the needle tip body  11 . A needle opening  12  is provided at the lower end of the needle tip body  11 . The needle opening  12  is a hole extending through the end wall of the needle tip body  11 . The needle opening  12  is communicated with the needle passage  100 . The sharp end  211  (see  FIG. 8 ) of the tattoo needle can extend out from the needle opening  12 . One capillary ink reservoir  13  is provided on the needle tip body  11  for maintaining and storing ink. The capillary ink reservoir  13  has at least one capillary ink containing body  14 . The ink for tattooing can be maintained and stored in the capillary ink containing body  14  of the capillary ink reservoir  13  by capillary action. The capillary ink reservoir  13  is adjacent to the needle opening  12 . The ink in the ink containing body  14  flows to the needle opening  12  directly and feeds to the sharp end  211  (see  FIG. 9 ) of the tattoo needle. 
     The ink reservoir  13  is integrally or detachably formed at the needle tip body  11 . The ink containing body  14  may be a plurality of capillary apertures. As depicted in  FIGS. 1 and 2 , the capillary apertures in the ink containing body  14  form grooves that extend generally transversal to the tattoo needle on the inner surface of the needle passage  100  at the needle opening  12 . As depicted, the grooves may be distributed along the full longitudinal extent of the needle opening  12 . The gap in the capillary apertures is a capillary gap, whereby the ink reservoir  13  can be used to absorb and retain ink by capillarity. 
     In different embodiments, the ink reservoir  13  may be formed of porous material, and the ink containing body  14  may have capillary pores in the ink reservoir  13  and have the function of capillarity. Alternatively, the ink reservoir  13  may be formed of fibrous material, such as a plurality of fibers, and the gaps between the fibers in the ink reservoir  13  may form the ink containing body  14  and may be capillary gaps with the function of capillarity. 
     Compared with the conventional cavity with smooth inner wall, the embodiment described above utilizes the capillary ink reservoir  13  to store and supply ink, which can store a large amount of ink, and does not easily cause leakage of ink. The ink reservoir  13  is located to be adjacent to the needle opening  12  with a plurality of ink containing bodies  14  being formed at the wall of the needle opening  12 . The ink in the ink containing body  14  flows to the needle opening  12  directly, without a special ink guide channel between the ink containing body  14  and the needle opening  12 . Compared with U.S. patent No. 20130226211 A1 and Chinese patent No. 202538157U, this embodiment of the present disclosure can improve flow of ink when ink with poor mobility and high viscosity passes through the ink guide channel. This embodiment can supply ink to the needle opening timely and sufficiently, whereby tattooists do not have to insert the needle tip into the ink cup deeply as Chinese patent No. 202538157U does for immersing the ink containing body when dipping ink. Ink with poor mobility and high viscosity is directly immersed to supply the ink containing body without passing through the ink guide channel, when tattooists are dipping ink. Thus, a tattooist may dip and add ink quickly and easily with this embodiment. 
     The ink reservoir  13  and the needle tip body  11  can be integrated and manufactured as one piece and connected thereon, or can be manufactured separately, then connected together. 
     As shown in  FIGS. 1-2 , in the embodiment, the needle opening  12  is in the shape of a hole, the ink reservoir  13  is adjacent to the needle opening  12 , the ink containing body  14  is a capillary slot directly formed in the wall of the needle opening  12 , and the ink in the ink containing body  14  flows to the needle opening  12  directly. 
     Please refer to  FIG. 3 , a combined device  501  according to the present disclosure includes a handle  301  and a tattoo needle tip  101  assembled to the handle  301 . The structure of the tattoo needle tip  101  is similar to the abovementioned tattoo needle tip  10  with the capillary ink reservoir. In the embodiment shown in  FIG. 3 , the handle  301  and the tattoo needle tip  101  with the capillary ink reservoir are integrated and manufactured as one piece. The combined device forms a combined component of a tattoo device, tattooists can install a tattoo needle on the combined device, and then install them to a tattoo machine for use. 
     As shown in  FIGS. 1-3 , the tattoo needle tip  101  with the capillary ink reservoir is connected to the handle  301  integrally. The handle  301  includes a holding body  311  and a handle neck  321  located at one end of the holding body  311 . One end of the needle tip body  110  distant from the needle opening  121  is integrally connected with the other end of the holding body  311 . Furthermore, the tattoo needle tip  101  includes the ink reservoir  131  having the ink containing body for maintaining and storing ink. A guide hole (not shown) is defined in the handle  301 . The guide hole extends through the handle neck  321  and the interior of the holding body  311  successively, and is in communication with the needle passage inside the tattoo needle tip  101 . 
     As shown in  FIGS. 4-5 , in combination with  FIGS. 1-2 , a combined device  502  according to another embodiment of the present disclosure is shown. A tattoo needle tip  10  with the capillary ink reservoir is installed at the handle  302  detachably. The handle  302  includes a holding body  312 , a handle neck  322  located at one end of the holding body  312 , and a needle tip installation portion  33  located at the other end of the holding body  312 . A guide hole  34  is defined to extend through the handle neck  322  and the holding body  312  successively, thereafter to communicate with the needle tip installation portion  33 . The tattoo needle tip  10  with the capillary ink reservoir can be detachably installed to the needle tip installation portion  33 . In the embodiment, the needle tip installation portion  33  is located in the guide hole at one end of the holding body  312 . The needle tip installation portion  33  has a containing slot  331 . Corresponding to the containing slot  331 , a snap-fit portion  111  is positioned on the outside of one end of the needle tip body  11  distant from the needle opening  12 . The snap-fit portion  111  of the needle tip body  11  is snap-fitted in the containing slot  331 , which forms a detachable locking mechanism of snap-fit style, so as to install the tattoo needle tip  10  to the handle  302  detachably. The needle tip body  11  and the needle tip installation portion  33  also can be installed by means of engagement of an axis and a hole, and so on. Instead of changing the handle, the detachable installation between the tattoo needle tip  10  and the handle  302  is convenient for tattooists to change tattoo needles of different specifications and needle tips adapted for tattoo needles of different specifications when tattooing. 
     Referring to  FIG. 6 , a combined device  503  according to a further embodiment of the present disclosure includes a needle tip casing  15  and the handle  303 . The needle tip casing  15  is installed to the handle  303  detachably. Meanwhile, in combination with  FIGS. 1-2 , the structure of the needle tip casing  15  and the handle  303  can be understood. In  FIGS. 1-2 , the capillary ink reservoir  13  and the tattoo needle opening  12  are integrated and manufactured as one piece, which forms the needle tip casing  15  shown in  FIG. 6 . Similar to the structure shown in  FIGS. 1-2 , the needle tip casing  15  includes an ink reservoir  133  for maintaining and storing ink. At least one capillary ink containing body  143  is provided in the ink reservoir  133 . The ink for tattooing can be maintained and stored in the ink containing body  143  of the ink reservoir  133 , and the ink reservoir  133  is adjacent to the needle opening  123 . The needle tip casing  15  is detachably installed to the needle tip body  113 , and the needle tip body  113  may be integrally or detachably connected to the handle  303 . The structure of the needle tip body  113  can be with reference to the needle tip body  11  shown in  FIGS. 1-2 . Users may install needle tip casings  15  adapted for tattoo needles of different specifications. 
     As shown in  FIGS. 7-8 , in combination with  FIGS. 1-2 , a combined device  40  in accordance with a further embodiment of the present disclosure includes a tattoo needle tip  10  and a tattoo needle  20  installed in the tattoo needle tip  10 . 
     As shown in  FIGS. 1-2 , the tattoo needle tip  10  includes a needle tip body  11 . A needle passage  100  is defined inside the needle tip body  11 . A needle opening  12  is defined at one end of the needle tip body  11  and extends through the end wall of the needle tip body  11 . The needle opening  12  is communicated with the needle passage  100 . An ink reservoir  13  is provided on the needle tip body  11  for maintaining and storing ink. At least one capillary ink containing body  14  is provided on the ink reservoir  13 . The tattoo needle  20  includes a needle head  21  and a needle bar  22  connected with the needle head  21 . Most of the tattoo needle  20  is contained in the needle passage  100  of the needle tip body  11 , and the sharp end  211  of the needle head  21  is located in the needle opening  12  when the sharp end  211  dips ink. In order to connect to an element driving the tattoo needle  20 , the needle bar  22  extends out of the needle passage  100  from one end of the needle tip body  11  distant from the needle opening  12 . The ink for tattooing can be maintained and stored in the ink containing body  14  of the ink reservoir  13 , and the ink reservoir  13  is adjacent to the needle opening  12 . A plurality of ink containing bodies  14  are formed in the wall of the needle opening  12 . The ink in the ink containing body  14  will directly flow to the needle opening  12  for feeding the sharp end  211  of the tattoo needle  20  to continue tattooing. 
     In the embodiment, the other end of the needle tip body  11  opposite to the needle opening  12  is an open end. Furthermore, a cover  16  is covered on the open end. A hole is defined in the cover  16  for the needle bar  22  of the tattoo needle  20  to extend out. 
     Referring to  FIG. 9 , and combining with  FIGS. 1-8 , a combined device according to a further embodiment of the present disclosure includes a tattoo needle tip  10 , a handle  302 , a tattoo needle  20  and a tattoo machine  60 . When in use, assemble the aforesaid tattoo needle tip  10  with the capillary ink reservoir, the tattoo needle  20  and the handle  302  together, connect the handle  302  to the tattoo machine  60 , and insert the needle bar  22  of the tattoo needle  20  into the guide hole of the handle  302  to connect to a driving element  61  connected to the tattoo machine  60 . Under the driving of the tattoo machine  60 , the driving element  61  drives the tattoo needle  20  to do a straight-line reciprocating motion in high frequency in the tattoo needle tip  10 , therefore, tattooists control the tattooing of the tattoo needle  20  by holding the handle  302 . The capillary ink reservoir  13  of the tattoo needle tip  10  is adjacent to the needle opening  12 , and the ink containing body  14  of the ink reservoir  13  is connected to the needle opening  12  directly. During operation, the tattoo needle  20  is doing a straight-line reciprocating motion in high frequency. The sharp end  211  of the needle wetted by ink rushes out from the needle opening  12  and stabs into the skin, then the sharp end  211  of the needle returns into the needle opening  12  and rushes out again with dipped ink. When adding ink, the tattoo needle tip  10  is inserted into a small ink cup, so that the ink immerses and fills the ink containing body  14  of the ink reservoir  13 . When tattooing, the ink in the needle opening  12  is continuously dipped by the sharp end  211  of the needle head  21  of the tattoo needle  20  and enters into the skin. The ink in the ink containing body  14  will be directly supplied to the needle opening  12  due to the capillary force and the motion of the tattoo needle  20 . The ink stored in the tattoo needle tip  10  by dipping and adding ink once can feed to the sharp end  211  of the tattoo needle  20  for many times of dipping. As a result, tattooists can avoid dipping ink frequently when tattooing. Moreover, it is quick and easy to dip and add ink. 
     By locating the ink reservoir at the needle tip, the above disclosed embodiment utilizes the capillary principle to store ink in the ink reservoir, which can store and retain a great amount of ink. Further, the ink storage grooves at the inner surface of the needle opening are extending transversely and the sharp end of the tattoo needle moves longitudinally across the ink storage grooves. Therefore, the leakage of ink is not easy to happen. The ink containing body of the ink reservoir is connected to the needle opening directly, and the sharp end of the needle continuously dips the ink in the needle opening via the reciprocating motion of the tattoo needle, realizing that dipping and adding ink once, the tattoo needle tip keeps tattooing for a longer time, so as to avoid dipping and adding ink frequently when tattooists are tattooing. Moreover, it is quick and easy to dip and add ink to the ink reservoir. 
     Although the tattoo needle tip described above and illustrated in  FIGS. 1-9  are convenient to use in some applications, tests have shown that in some cases drawing of the ink from the ink storage grooves may be interrupted even when there is still substantial ink in the storage grooves. 
     It has been recognized that, as illustrated in  FIGS. 10A to 10C , depending on the needle or needle bundles used in the particularly application, the gap between the tattoo needle sharp end and the inner surface of the needle passage or opening  12  may be too big to continuously draw ink out of the ink storage grooves and maintain continuous and efficient ink flow from the ink storage grooves to the needle opening  12  and tattoo needle. 
     More specifically, as illustrated in  FIGS. 10A and 10B , when the needle head  21  is centrally positioned in the needle opening  12 , the gap between the needle head  21  and the inner surface of needle opening  12  is generally uniform. For a given size or diameter of the needle opening  12 , this gap can vary depending on the size(s) of the individual needles, the number of needles used, the arrangement and spacing between the needles, and possibly other factors. For example, during manufacture a plurality of needles may be welded or soldered together to form the needle head  21 . As better depicted in  FIG. 10B , five needles are included in the example needle bundle shown, for illustration purposes. The sizes of the individual needles and the packing of the needles and their overall size may vary due to different manufacturing or engineering tolerances and different arrangements of the needles in the bundle. In some cases, the amount of soldering or welding materials left between the needles may vary due to various reasons. These variations can result in different diameters or overall sizes of the needle head  21 , and variations in the gap between the needle head  21  and the inner surface of needle opening  12 . 
     In addition, the gap between the needle head  21  and the inner surface of needle opening  12  will become smaller if more needles, such as seven or eight needles, of the same needle size are included in the needle bundle. The gap will become larger if fewer needles, such as four or three needles, of the same needle size are included in the needle bundle. If each needle has a larger diameter, even for the same number of needles, the gap will become smaller. If each needle has a smaller diameter, even for the same number of needles, the gap will become larger. During manufacture and operation, the user may prefer to be able to adjust the number of needles and the needle sizes without changing the needle tip body or other parts of the needle assembly. As a result, the gap between the needle and the inner surface or the grooves may vary, which in turn affects the ink drawing performance. When the gap is too large, even if there is still some capillary action, the ink drawing effect may be too small or weak to maintain continuous and efficient ink drawing from the grooves even when there is still plenty of ink left in the grooves. 
     The situation may become worse if the needle head  21  is being pushed away from the grooves as illustrated in  FIGS. 10C and 10D , where the needle head  21  is in contact with the inside of the needle opening  12  that is opposite to ink containing body  14  of the ink reservoir  13 . In this case, the gap between the needle head  21  and the ink reservoir becomes larger and capillary drawing of the ink from the ink reservoir  13  is reduced or even terminated. Such a situation may occur during operation when the operator presses the tattoo needle against the skin and moves in different directions. Such a situation may also occur if the needle head  21  is biased by something in the needle module for other reasons. 
     To prevent such inefficient usage of the stored ink, in an improved embodiment, a biasing member may be provided to bias the tattoo needle or needle head towards the inner side of the needle opening where the ink storage grooves are located or nearby to reduce the capillary gap between the sharp end of the tattoo needle and the grooves, and to maintain a smaller capillary gap during operation, so as to continuously draw ink out of the grooves by improved capillary action. As can be understood, a smaller capillary gap can provide improved and more reliable capillary action to improve drawing of the ink from the ink storing grooves. 
     For example, a specific embodiment of such a device is provided in a needle module  1010  as illustrated in  FIGS. 11 to 14C . 
     As depicted in  FIGS. 11 to 13A , needle module  1010  includes a needle housing  1040  for movably mounting a needle bundle  1200  therein. As can be appreciated, the needle housing  1040  can be considered to be a needle tip body. The needle housing  1040  is formed by a tubular body portion  1400 , a mouthpiece  1100  and a cap  1500 . Housing  1040  has a tubular longitudinal channel  1420  therein. The channel  1420  has an upper open end  1422  and a lower open end  1424 . A mouthpiece  1100  with an opening  1120  is provided at the lower end  1424  and a cap  1500  is provided at the upper end  1422 . Mouthpiece  1100  has a guide surface  1122  (see  FIG. 13A ) for guiding movement of the needle and feeding ink to the needle, as will be detailed below. It is sufficient to note here that the guide surface has ink storing grooves thereon and the grooves are positioned on the opposite side as compared to the ink reservoir  13  on the needle tip body  10  shown in  FIGS. 1-10D , as can be best seen by comparing  FIG. 10C  and  FIG. 13A , and comparing  FIG. 10D  and  FIG. 14D . The channel  1420  may be formed with a tubular body portion  1400 , which may have an observation window  1410 . Channel  1420  has a longitudinal axis denoted as axis A in the figures. The opening  1120  in the mouthpiece  1100  has a longitudinal axis denoted as axis A 1  in the figures. 
     Mouthpiece  1100  and cap  1500  may be connected and engaged with the lower and upper ends of body portion  1400  in any suitable manner, with any suitable engagement or locking mechanism. For example, these parts may be engaged by tabs, threads, clamps, pins, keys, and corresponding openings, notches, threads, holes, keyways, or the like as can be understood by those skilled in the art. As depicted, both mouthpiece  1100  and cap  1500  may frictionally engage the inner walls of body portion  1400 , and are interlocked in the mounted positions with a tab. For example, as illustrated in  FIG. 12 , the housing body portion  1400  may include a mating notch  1426  at the lower end  1424 , and the mouthpiece  1100  may include a corresponding mating stab  1126  that matches and mates with the mating notch  1426  for orienting and positioning the mouthpiece  1100  in relation to the housing body portion  1400 . 
     As will be appreciated and as in conventional needle modules, needle bundle  1200  is housed and guided in housing  1040  in a manner to allow the needle bundle  1200  to reciprocally move up and down during use. The detailed construction and mechanism for such mounting and reciprocal movement are not the focus of this disclosure, and can be implemented by a skilled person in the art according to known techniques or constructions, except in aspects specifically described below. Thus, some of these details will not be discussed herein. 
     It is noted that, however, to facilitate the reciprocal movement of the needle bundle  1200 , a biasing member such as a resilient band  1300  is also provided and configured to pull the needle bundle  1200  up during each movement cycle after the needle bundle  1200  is pushed down by an actuating or driving mechanism such as a drive shaft (not shown but see  FIG. 16  to be discussed later). In an embodiment in the present enclosure, the biasing member such as band  1300  is not only used to facilitate reciprocal movement of the needle bundle  1200 , but also used to bias the needle bundle towards the guide surface  1122  to maintain contact or a smaller capillary gap between the needle bundle  1200  and the stored ink in the ink reservoir as will be made clearer below. 
     As will be understood, needle module  1010  can also be considered as a needle assembly. While the depicted device is referred to as a needle module, it is only used to illustrate an embodiment of possible needle assemblies. In different embodiments, an embodiment of the present disclosure may be used in any number of different types of needle assemblies. 
     Returning to  FIGS. 11 and 12 , as depicted, needle bundle  1200  includes a tip portion  1210  (also referred to as the sharp end of the needle), a needle shaft portion  1220 , a hook structure  1230 , and a shaft  1240 . 
     Tip portion  1210  may include one or more sharp pricking needles, which may be welded or soldered together, or otherwise bounded together. The pricking needles may be formed of stainless steel or any other suitable material. The individual pricking needle may have any suitable or known needle sharp end shape. The pricking needles may be arranged to form a tip portion that has a generally or substantially cylindrical or conical profile. Alternatively, the pricking needles may be arranged side-by-side to form a tip portion that has a generally flattened or band-shaped profile. Rows of side-by-side needles may also be stacked. Such different arrangements of tattoo needles are known in the art and may be referred to as “Round Liner” needles, “Round Shader” needles, “Flat” Needles, or “Magnum” needles, respectively. Tip portion  1210  may include 1-18 individual pricking needles for “Round Liner” needles and “Round Shader” needles, or may include 4-27 pricking needles for “Flat” needles and “Magnum” needles. 
     As can be appreciated, the cross-sectional sizes or diameters of the needles or needle bundles will affect how the ink will flow. Typically, the smaller the pricking needle size or narrower the diameter of the pricking needle, the finer and more controlled the stream of ink that flows off each pricking needle. Typically, the pricking needles in the same needle bundle may be of the same or similar sizes. The size of the pricking needles may be selected based on the desired effects by the operator or user. Different sizes may be used for different reasons. Standard sizes of pricking needles may be used. The diameters of the individual pricking needles may be 0.25 mm, 0.30 mm, or 0.35 mm in some embodiments. The designs of the pricking needles may be selected and vary as known in the art based on the desired tattooing techniques and purposes to be applied. 
     The number of pricking needles in a needle bundle may vary from 1 to 27 or more as desired. For example, commercially available round needle bundles typically have 1, 3, 5, 7, 8, 9, 11, 14, or 18 pricking needles in each bundle. It would also be appreciated that the overall profile of the needle bundle may change and vary depending on the number of pricking needles in the bundle, their arrangement, the amount of soldering material used, or other factors. 
     The pricking needles in a bundle may be welded together, such as by lead-free soldering. 
     As can be seen in  FIG. 12 ,  FIGS. 13A and 13B , and  FIGS. 17A and 17B , the welded pricking needles in tip portion  1210  are supported on needle shaft portion  1220 . The axis of needle shaft portion  1220  and the axis of shaft  1240  are aligned with the axis A of the channel  1420  in the housing body portion  1400 , but are off-set from axis A 1  of the opening  1120  of the mouthpiece  1100  and the axis of needle tip portion  1210 . The needle shaft portion  1220  may be formed of stainless steel or another suitable material. It should be sufficiently rigid and strong to support stable movement of the needle tip portion  1210  during operation. Tip portion  1210  may be welded onto needle shaft portion  1220 . 
     Needle shaft portion  1220  is joined with shaft  1240  for driving the tip portion  1210 . Shaft  1240  may be formed of a plastic material or another suitable material for transmitting the axial driving force to needle shaft portion  1220  and then indirectly to tip portion  1210 . As depicted in  FIGS. 17A and 17B , shaft  1240  may include a cylindrical bore  1242  for receiving the needle shaft portion  1220  at the lower end of the shaft  1240 . Needle shaft portion  1220  may be inserted into the bore  1242  and may be attached to the wall of the bore  1242  of the shaft  1240  with an adhesive, such as glue. At the bottom end of the shaft  1240 , a hood-shaped hook  1230  is provided adjacent to the bore opening of bore  1242 . The hook  1230  is shaped and sized to accommodate and retain a section of the elastic band  1300 , which is looped around needle shaft portion  1220  during assembly and is retained between needle shaft portion  1220  and hook  1230 . As can be appreciated, other forms or structures may also be used to retain band  1300 . The hood-shaped hook  1230  provides a secure retaining mechanism for retaining the band  1300  when needle bundle  1200  moves up and down, as it prevents accidental release of the band section over the hook  1230  due to fast relative movement of the parts. 
     Hook  1230  may be replaced by a hook mounted on shaft  1240  in a different embodiment. 
     The cap  1500  may be made of a plastic material, or any other suitable material. As better seen in  FIGS. 18A and 18B , cap  1500  has a through opening  1520  that allows the shaft  1240  to axially move therethrough. A stub  1530  is provided on cap  1500 , which stub faces the inner wall of in the body portion  1400  of the housing  1040 . 
     As illustrated in  FIGS. 13A and 13B , a section of the band  1300  may be looped around the stub  1530  on the cap  1500 , and retained between the stub  1530  and the inner wall of the body portion  1400  of the housing  1040 . 
     An elastic looping band  1300  is provided, which, when the needle module  1010  is assembled, is looped around at one end hook  1230  and at the other end around stub  1530 , so that band  1300  is hooked by hook  1230  and stub  1530  so that band  1300  is retained in place but can expand and contract when the needle bundle  1200  moves up and down during operation. The hook  1230  and stub  1530  are configured and oriented during assembly such that when band  1300  engages both hook  1230  and stub  1530 , band  1300  biases the needle bundle  1200  upward and biases the tip portion  1210  against the guide surface  1122  in the mouthpiece  1100 . Band  1300  may be formed of a silicone band, or a band formed of another resilient material such as latex or rubber. Band  1300  may be in the shape of an O-ring when in a relaxed state. 
     As better illustrated in  FIGS. 13A to 13C , the band  1300  is normally positioned and oriented at a slight angle relative to the axial direction of shaft  1240 , in the F direction as shown in  FIG. 13B . For easier viewing, the mouthpiece  1100  and body portion  1400  are not shown in  FIG. 13B . The band  1300  is normally slightly tensioned to bias the needle bundle  1200  upward (i.e. to retract) and bias the tip portion  1210  against the guide surface  1122 . When the needle bundle  1200  is pushed downward by a drive shaft (not shown) through shaft  1240 , the band  1300  is further stretched and provides an increased axial biasing force upward (component F 2  as illustrated in  FIG. 13C ). However, the radial component of the biasing force (F 1  shown in  FIG. 13C ) against the guide surface  1122  will not change significantly during axial movement of the needle bundle. 
     As can be appreciated, the inner diameter of the through opening  1520  in cap  1500  may be sized to be larger than the outer diameter of the shaft  1240 , and there may be gap  280  between the shaft  1240  and the inner wall that defines opening  1520 . Such a gap may allow smooth movement of the needle bundle  1200  and shaft  1240  in the housing  1040 , reducing or preventing the risk of jamming or too much friction. Such a gap also allows the shaft  1240  and needle bundle  1200  to lean at a slight angle off the axial direction (axis-A). 
     Under the biasing force (denoted by F 1  as shown in  FIG. 13C ) exerted by the band  1300 , the tip portion  1210  at the bottom end of needle bundle  1200  is pressed towards guide surface  1122 . A slight lean of needle bundle  1200  off the axial direction of the axis A or A 1  would reduce the stress and bending of needle bundle  1200 . 
     As depicted, the axis A 1  of opening  1120  and the needle tip portion  1210  is offset from the axis A of the shaft  1240  and needle shaft portion  1220 . The mouthpiece  1100 , needle shaft portion  1220 , shaft  1240 , body portion  1400  and cap  1500  may be co-axial in some embodiments, as depicted in  FIG. 13A  (aligned along axis A). As depicted in  FIGS. 11 and 13A , the axis A 1  is offset from the axis A towards the observation window  1410 , so that the axis A 1  is closer to the observation window  1410  than the axis A. The distance between axis A and A 1  may be from about 1.2 mm to about 1.8 mm. The needle module  1010  is typically held by the operator so that the observation window  1410  is facing the operator during operation. As depicted, when the needle module  1010  is properly assembled, the observation window  1410  and the guide surface  1122  are on opposite sides of the axis A 1 . 
     In different embodiments, the shaft  1240  and needle shaft portion  1220  may also be offset and non-coaxial. In such cases, the offset distance between the axis A 1  and the axis A may be even larger, such as about 2 mm to about 3 mm, or up to 5 mm. 
     The mouthpiece  1100  is configured to support and allow axial movement of the needle tip portion  1210  through the opening  1120 . The mouthpiece  1100  may be made of a plastic material or another suitable material. The opening  1120  may have a shape configured to match the profile of the tip portion  1210  of needle bundle  1200 . For example, for round or circular tip portion  1210 , the opening  1120  may have a circular or diamond shape; for flat tip portion  1210 , the opening  1120  may have a rectangular shape. 
     As depicted in the drawings, the mouthpiece  1100  and housing body portion  1400  may be generally co-axial (along axis A) but the axis A 1  of the opening  1120  may be offset from axis A of channel  1420 . As can be appreciated, when the axis A 1  of the opening  1120  is offset from the axis A of the channel  1420 , the needle tip portion  1210  is also offset from axis A to align with the opening  1120 . Conveniently, the embodiment as depicted allows the operator to better see the position of the sharp needle end(s) during operation. To allow improved observation, mouthpiece  1100  may be made of a transparent material, such as a transparent plastic. The offset of the opening  1120  with respect to the channel  1420  also provides more space to accommodate larger ink storage grooves  1110 , thus providing higher storage capacity. 
     The size of opening  1120  is also selected to accommodate the size of the tip portion  1210 . To avoid jamming during use and to accommodate different needle sizes or needle bundle sizes, the size of the opening  1120  of the mouthpiece  1100  may be selected to allow some play of the largest needle bundle to be used. That is, the size of opening  1120  is slightly larger than the size of the needle tip portion  1210 , so that there is a gap between the inner wall of opening  1120  and the needle tip portion  1210  on the opposite side of the guide surface  1122 . This gap allows smooth movement of the needle tip portion  1210  and size variations of the tip portion  1210 , without jamming. 
     Even though there is a gap between the needle tip portion  1210  and the opening  1120 , the risk that the tip portion  1210  will vibrate sideways is low as the tip portion  1210  is biased against the guide surface  1122 , which provides a stable support surface for the movement of the tip portion  1210 . In other words, even when the size of the opening  1120  is relatively large, and there is a gap between the tip portion  1210  of the needle bundle  1200  and the inner surfaces of the mouthpiece  1100 , the biasing force F 1  causes the tip portion  1210  to contact and abut against the guide surface  1122 , and maintain the contact during operation (reciprocal movement of the needle bundle  1200 ). 
     Mouthpiece  1100  is also configured to function as an ink feeding device. Specifically, as illustrated in  FIG. 13A , and in  FIGS. 14A to 14D , ink storage grooves  1110  defined by groove walls  1125  are provided on guide surface  1122 , for storing ink. Each groove  1110  extends generally transversely in relation to the axial direction and the direction of movement of the needle bundle  1200 . Groove walls  1125  and grooves  1110  may be generally parallel to one another, and are located near, but above, the lower open end of mouthpiece  1100 . Grooves  1110  may extend radially to the external surface of the mouthpiece  1100  to allow easy filling of ink during use. That is, each groove  1110  may be open to the external surface of mouthpiece  1100  as depicted in these figures. Each individual groove  1110  is formed between two opposing groove walls  1125  having a thin gap between the opposing groove walls  1125  such that when the mouthpiece  1100  is brought into contact with an ink source (such as when it is dipped in an ink bottle), ink can be sucked into and fill the gap due to capillary action. The ink in the gap can be normally retained in place due to surface tension and adhesion of the ink liquid to the groove walls  1125 . 
     However, when the tip portion  1210  of the needle bundle  1200  moves downward across the grooves  1110  while being pressed against the guide surface  1122 , the moving needles will contact the liquid surface of the ink stored in the grooves  1110  and bring ink out of grooves  1110 , and then carry the ink with the needles or allow the ink to flow along the needles and be applied to the skin. Close contact with the guide surface  1122  also facilitates flow of the ink into narrow gaps  1150  (see  FIG. 14D ) that exist between the needles in the needle bundle  1200  and the guide surface  1122 . 
     For example, as better illustrated in  FIGS. 14B and 14D  (also see  FIG. 14C ), in an example bundle of seven (7) needles, it is possible that only the bottom needle is in contact with the guide surface  1122 , at a point  1121 . A section of the bottom needle may be in contact with the guide surface  1122  between the grooves  1110 , and may extend across the grooves in a direction that is particular to the traversal directions along which the grooves  1110  extend. However, narrow gaps  1150  also exist between the curved guide surface  1122  and some of the needles in tip portion  1210  of the needle bundle  1200 . A much larger gap is present between the tip portion  1210  and the opposite wall surface  1124  of the inner channel of the mouthpiece  1100  as depicted in  FIG. 14B  (also see  FIG. 14D ). 
     The grooves  1110  are also open at the guide surface  1122 , with ink contacting openings  1112 . The width of each ink contacting opening  1112  may be about 0.3 mm to 0.6 mm. The width may vary and may be selected based on the ink fluid properties. In a particular embodiment, the width of opening  1112  may be about 0.4 mm. 
     The number of grooves  1110  may also vary and may be selected based on a number of factors, such as the amount of ink to be applied and the size and length of the needles used, and production or manufacturing considerations. In some embodiments, there may be 3 to 12 grooves, such as 5 to 10 grooves. 
     The contact opening  1112  of each groove  1110  at the guide surface  1122  may extend circumferentially by a selected angle θ around the axial direction (see axis A 1  in  FIG. 11 ). The contact opening  1112  may extend symmetrically about the contact point  1121 , by an angle of X on each side (see  FIG. 14D ), where θ=2X. In different embodiments, angle θ may vary from about 120° to about 360°. For example, angle θ may be about 120°, 140°, 160°, 180°, or 200°. 
     The external openings of grooves  1110  may extend circumferentially at similar angles or larger angles. As depicted in  FIGS. 14B and 14D , in an embodiment, the external openings of grooves  1110  may extend continuously, and may be limited/defined by a wall  1123  that extends along the line between the ends of the contact opening  1112 . 
     In alternative embodiments, the external openings of grooves  1110  may be segmented, as illustrated in  FIGS. 15A, 15B and 15C . 
       FIG. 15A  illustrates a portion of a variant of the mouthpiece  1100 ′ having ink storage groove  1110 ′ with contact opening  1112 ′, the angle θ is 360°, an opening  1120 ′, a guide surface  1122 ′, and an opposite surface  124 ′. Needle bundle tip portion  1210  is received in opening  1120 ′, and contacts the guide surface  1122 ′ at contact point  1121 ′. There is a narrow gap  1150 ′ between tip portion  1210  and the guide surface  1122 ′ around the contact point  1121 ′. In  FIG. 15A , the external opening is separated by solid sections  1115 . Sections  1115  provided at opposite sides can provide reinforcement of the structural integrity. It is possible to have a section  1115  at only one side, in which case, however, the mechanical strength of the structure may be reduced and the mouthpiece  1100  may be easier to bend or deform. 
       FIG. 15B  illustrates a portion of a variant of the mouthpiece  1100 ″ having ink storage groove  1110 ″ with contact opening  1112 ″, an opening  1120 ″, a guide surface  1122 ″, and an opposite surface  124 ″. Needle bundle tip portion  1210  is received in opening  1120 ″, and contacts the guide surface  1122 ″ at contact point  1121 ″. There is a narrow gap  1150 ″ between tip portion  1210  and the guide surface  1122 ″ around the contact point  1121 ″ and at contact opening  1112 ″. In  FIG. 15B , the external opening is separated by a reinforcing section  1116 , which can increase the structural strength and prevent or reduce bending or deformation. 
       FIG. 15C  illustrates a portion of a variant of the mouthpiece  1100 ′″ having ink storage groove  1110 ″ with contact opening  1112 ′″, an opening  1120 ′″, a guide surface  1122 ′″, and an opposite surface  1124 ′″. Needle bundle tip portion  1210  is received in opening  1120 ′″, and contacts the guide surface  1122 ′″ at contact point  1121 ′″. There is a narrow gap  1150 ′″ between tip portion  1210  and the guide surface  1122 ′″ around the contact point  1121 ′″ and at contact opening  1112 ′″. 
     In  FIG. 15C , fluid conduits  1105  are provided on groove walls  1125 ′″ to allow fluid communication between different grooves  1110 ′″. Conduit  1105  thus connects grooves  1110 ′″. The width of conduit  1105  is smaller than the width of the groove  1110 ′″. For instance, if the groove  1110 ′″ has a width of 0.4 mm, conduit  1105  may have a width of about 0.3 mm. 
     In other embodiments, conduit  1105  may be deeper or shallower, and may even extend all the way to the guide surface  1122 ′″ so that ink may be fed directly to tip portion  1210 , as illustrated in  FIG. 15E . 
     As can be appreciated, section  1115  or  1116  may provide a stronger construction and stabilize the groove walls  1125 , and thus the gaps therebetween, although providing section  1115  or  1116  may reduce the ink storage volume in the grooves  1110 . 
     In the embodiment illustrated in  FIG. 15B , the bottom needle or the tip portion  1210  of the needle bundle  1200  may be in continuous contact with the guide surface  1122 ″ at contact point  1121 ″. Section  1116  may be formed of a reinforcing material to improve the mechanical strength of the mouthpiece. The guide surface at the section  1116  may also be smooth, and may optionally be provided with special surface treatment for reduced friction between the needle(s) and the guide surface  1122 ″. 
     With the added section  1115 , or  1116 , it is also possible to further extend the circumferential angle of each groove  1110 ′ or  1110 ″, as illustrated in  FIGS. 15A and 15B  respectively, such as to an angle higher than 180° or is 360°. Groove wall  1123 ″ may also extend at an angle relative to the line between the ends of the contact opening  1112 ″, to allow larger external openings for easier ink filling and increased ink storage capacity. 
     As illustrated in  FIG. 15D , it is possible in some embodiments that some portions of the bottom needle are not in contact with the guide surface  1122 , but is very close to the guide surface  1122  due to the biasing force (F 1 ), separated by a small distance “y”. As long as the gap y is small enough, ink may still be drawn from ink storage grooves  1110 . A benefit of no-contact between the needle and the guide surface  1122  is that there is reduced or no friction. 
     Needle module  1010  may be pre-sterilized and packaged to keep it clean during storage and transportation. 
     The needle module  1010  and its parts may be manufactured from suitable materials based on technologies known to those skilled in the art. For example, various parts in the needle module  1010  may be made from corresponding materials used in conventional needle modules, such as those used in tattooing needle modules. The parts may be formed and machined using known processing techniques, as can be understood by those skilled in the art in view of the present disclosure. 
     During use, needle module  1010  is installed on a corresponding tattooing device. For example, as illustrated in  FIG. 16 , needle module  1010  may be coupled, through or by a needle handle  1020 , to a base device  1030 . 
     The base device  1030  may typically include a needle actuator with a drive shaft  1035  for actuating and driving the needle tip portion  1210  through shaft  1240 . 
     The handle  1020  may have a generally tubular shape, and may be cylindrical. 
     The handle  1020  and base device  1030  may be constructed and operated as disclosed in U.S. patent application Ser. No. 15/691,125 by Xiao, the entire contents of which are incorporated herein by reference. 
     The assembled needle module  1010 , handle  1020 , and base device  1030  form an ink applicator  1060 , or in particular, a tattooing device. 
     During operation, an operator may hold the ink applicator  1060  with handle  1020  in her hand, and dip the mouthpiece  1100  in an ink container (not shown) to fill the ink storage grooves  1110  with the desired ink. The needle actuator is activated to drive the drive shaft  1035  and consequently needle shaft  1240  and tip portion  1210  of the needle bundle  1200  downward. After each downward stroke, the resilient band  1300  is stretched and pulls the tip portion  1210  back up once the drive shaft  1035  stops the downward movement and moves upward. The needle actuator then re-starts the downward drive in the next cycle. This process repeats so as to drive the needle bundle  1200  to reciprocally move longitudinally along the axial direction of the shafts  1035  and  1240 . The base device  1030  may be configured to operate at a drive frequency of about 80 to 150 Hz. The operator may adjust the operating frequency during operation. In some tattooing machines, the tattoo needles may be operated to puncture the skin from 50 to 10,000 times per minute. The needles may penetrate the skin and reach a depth of about 1 mm. The vertical moving distance of the drive shaft  1035  is typically about 2 mm to 5 mm, and the needle bundle  1200  may similarly move about 2 to 5 mm during each stroke. 
     In different embodiments, drive shaft  1035  may be connected to needle bundle  1200  through a coupling member (not shown). During a stroke, drive shaft  1035  may push needle bundle  1200  downward, and thus stretch the band  1300 . After reaching the bottom of the stroke, the drive shaft  1035  and band  1300  will both pull needle bundle  1200  back up. 
     As the tip portion  1210  moves up and down, the operator may bring it to contact a subject&#39;s skin to apply ink to the skin, as in a conventional operation, which can be understood by those skilled in the art. 
     As discussed above, due to the biasing force (F 1 ) applied by band  1300 , tip portion  1210  is biased against the guide surface  1122  in mouthpiece  1100  while moving up and down due to the longitudinal reciprocal movement, and can draw ink out of ink storage grooves  1110 . 
     After each operation or use, the needle module  1010  may be removed and disposed. The handle  1020  may be next removed, and may also be disposed. The operator can take off disposable gloves and clean her hands at this time before touching other parts of the ink applicator  1060 . 
     For the next operation, a new needle module and new handle may be connected to the base device  1030 , and used similarly as described above. 
     The needle module  1010  may be used directly after opening the needle module packaging without further cleaning, sanitization, or sterilization, and can be disposed after a single use without cleaning or any other treatment. 
     Conveniently, ink flow from grooves  1110  to the sharp end of the tip portion  1210  may be stable and consistent, when there is still sufficient ink in grooves  1110 . Ink residue in the grooves  1110  before re-fill can be reduced, as compared to some conventional ink feeding techniques. More efficient use of the ink and ink fill is thus possible. 
     As the contact openings  1112  of grooves  1110  extend perpendicular to the axial direction of tip portion  1210  and its movement direction, it is unlikely the tip portion  1210  may stuck in a groove  1110 . In comparison, if the ink storage groove is parallel to the needle movement direction, the needle may be more likely to get stuck in the groove. 
     Further, a tattoo operator tends to hold the needle in a relatively vertical orientation or an inclined orientation close to the vertical orientation. When the grooves run parallel to the needle movement direction, i.e., vertical or nearly vertical during operation, the ink in the groove may tend to flow downward due to gravity. To prevent such undesired ink flow, the vertical grooves will need to be narrower to limit the effect of gravity. In comparison, as the groove walls  1125  between the grooves  1110  are positioned horizontally or close to horizontal during operation, gravity will have less effect on the fluid flow in the grooves  1110 . As a result, relatively larger grooves (or gaps between groove walls) may be used for ink feeding in an embodiment of the present disclosure, and consequently, the amount of ink stored during each fill or re-fill is increased as compared to some conventional ink feeding devices. 
     With perpendicular grooves, the number of grooves may also be varied, and increased as compared to vertical grooves. With vertical grooves, the number of vertical grooves is limited due to the limited diameter of the needle size (or size of the needle bundle). Tests have shown that with vertical grooves, while the grooves directly in contact with the needle tended to allow excessive ink flow, the grooves not in direct contact with the needle tended to keep excessive residual ink even when the needle was no longer delivering ink to the skin. That is, vertical grooves further away from the needle are not very effective for feeding ink. Such limitation and problems do not exist with particular grooves in an embodiment disclosed in the present disclosure. 
     It might have been expected that perpendicular groove orientation is not as effective as the needle would need to travel across groove edges, which might have been expected to cut off ink flow, so that it might have been expected that perpendicular groove orientation should not be used. However, tests have surprisingly shown that example embodiments as disclosed herein could deliver and feed ink more stably and consistently, and could address a number of drawbacks of conventional feeding techniques discussed herein. 
     For example, without being limited to a particular theory, it is expected that, while the ink flow from grooves  1110  in a vertically held needle bundle  1200  may be mainly due to capillary action (gravity effect is limited by the horizontal groove walls  1125  as discussed above), since the small gaps  1150  between the guide surface  1122  and needle tip portion  1210  may be smaller than the groove width in grooves  1110 , the capillary force in the gaps  1150  may be larger than the capillary force in the grooves  1110 . As such, ink will likely be drawn out of the grooves into the small gaps  1150  due to such force differential. Ink residual in the grooves  1110  may be reduced as a result. 
     Another convenient effect of an embodiment disclosed herein is that the size of the opening  1120  in the mouthpiece  1100  may be adjusted with more flexibility. Due to the biasing force applied to the tip portion  1210  by the band  1300 , contact and alignment of the tip portion  1210  with guide surface  1122  may be more conveniently maintained without a close-fit opening  1120 . With a larger opening  1120 , it is possible to reduce friction between the needle tip portion  1210  and the wall surface at opening  1120 . 
     For clarity, it is noted that “single use” may refer to use of a needle or needle module for one complete operation on a single individual subject. During this operation, different needle modules may be used to apply different ink colors or for different purposes. For example, it may be typical to use two to five different types of needles during a single operation on a subject, depending on the complexity of the design to be applied. 
     As can be appreciated, various modifications may be made to the example devices illustrated in the drawings. 
     For example, band  1300  may be formed of any suitable material with suitable strength and resiliency. Further, the O-ring and hook structure may be replaced with another biasing mechanism or structure. Other biasing members known to skilled persons in the art may also be used as long as they provide the desired biasing force to draw back the needle and bias the tip portion against the guide surface  1122 . In some embodiments, separate biasing members may be used to separately provide the longitudinal biasing force F 2  and the radial biasing force F 1  (see  FIG. 13C ). However, as can be appreciated, band  1300  conveniently provides both biasing forces with a simple construction structure. Alternative biasing members may include elastic bands, springs, resilient stabs, or the like. Suitable resilient materials may include silicones, rubbers, latex, plastics, metals, or the like. 
     To further reduce friction and possible adverse edge effects at the edges of contact openings  1112 , the edges at openings  1112  may be treated for smooth contact, and may be rounded to eliminate sharp edges. As described above, directed contact maybe limited or reduced to a small contact point. However, when the needle bundle does not directly contact the guide surface, the distance between the needle and the guide surface should be relatively small, such as below 0.15 mm, to allow the needle to draw ink out of the grooves  1110 . As noted above, a further alternative to avoid or limit edge effect, is to provide a smooth guide surface at the contact point, such as illustrated in  FIG. 15B  and  FIG. 15C . 
     In some embodiments, the groove walls  1125  in grooves  1110  may be provided with cavities or holes (not shown) to store more ink. Ink storage grooves may include smaller segments of openings arranged in rows and columns. Such openings may have circular, rectangular, oval or other profiles or shapes. The arrangement of the openings and grooves may be regular or irregular. The tip portion  1210  may be biased toward and to move across the arrangement of the openings so as to draw out ink by capillary action. 
     As the amount of stored ink may be increased, while reducing the risk of excessive residual ink or unstable ink flow, an embodiment of the needle assembly disclosed herein may allow an operator to fill the ink less frequently, and reduce the operation time. 
     As now can be appreciated, when guide surface in the mouthpiece is shaped to conform to an external profile of the needle bundle, the contact area between the needle bundle and the ink stored in the grooves can be increased. 
     As described herein, the circumferential angle refers to the angle formed by two lines from the center of a circle to two points on the circumference of the circle. It should be noted that, however, in practice, the parts in the disclosed devices may not have perfect circular shapes, and the profiles of the parts may be generally circular and the angles may be approximate. 
     The longitudinal channel in the housing may be considered to have a generally circular profile even if the profile is not a perfect circle. In some embodiments, the longitudinal channel may have a generally polygonal profile, which is not necessarily perfect polygon. For example, the profile may be generally rectangular or a diamond shape, but the edges may be no-linear. 
     In some embodiments, the ink storage grooves may have a width of about 0.3 mm to about 0.6 mm, but in other embodiments the width may be wider or narrower. 
     As depicted in the figures, the housing in the needle module may include a generally conical lower portion (mouthpiece) and a generally cylindrical upper portion (body portion). However, in different embodiments, the housing and any of its components may have different shapes and sizes. 
     The ink storage grooves may be separated and isolated by groove walls, or may be inter-connected via channels or holes through the groove walls. The groove walls may also be perforated. The connecting channels and holes may be sized for capillary action, or may have relatively larger sizes as it is not necessary that the fluid communication between the grooves through the groove walls are effected by capillary action. Interconnected grooves may allow faster and more uniform ink loading and distribution along the needle length, and hence more effective ink feeding. 
     As described earlier, in an embodiment, the tip portion of the needle bundle may not contact the inner surface of the mouthpiece during operation. In such cases, the housing may include a tubular longitudinal channel and an inner surface. The channel has an upper open end and a lower open end, a plurality of ink storage grooves for storing ink by capillary action extending generally transversely in the inner surface above the lower open end. A needle bundle is mounted in the housing, which includes one or more needles longitudinally reciprocally movable in the longitudinal channel and are biased towards the inner surface across the grooves to form a capillary gap (such as the gap with gap distance y as illustrated in  FIG. 15D ) between the needle bundle and the inner surface, for drawing ink out of the ink storage grooves during longitudinal reciprocal movement of the needle bundle across the grooves. 
     In some embodiments, the ink storage grooves may be closed to the exterior surface of the mouthpiece, and an ink container may be provided and placed in fluid communication with the grooves, such as via an internal fluid conduit though the groove walls. The ink container may be external to the needle module, in which case, the ink container may be connected to the internal fluid conduit by a tube. The ink container may also be installed within the housing in the needle module, or attached to the handle or another part of the ink applicator. 
     While the above examples are illustrated in the figures with a round tip portion or round needles and needle bundles, in different embodiments, the construction of the needle module may be readily modified or adapted to use flat or Magnum needles. In the latter case, the mouthpiece may typically have a generally rectangular mouth opening, as illustrated in  FIGS. 19A, 19B and 19C . The example needle module  1010 ′ illustrated in these figures has a bundle of 15 needles arranged in two flat rows. The needles may be welded together. The needle module  1010 ′ includes a needle housing  1040 ′ for movably mounting a needle bundle  2000  therein. The needle housing  1040 ′ is formed by a tubular body portion  1400 , a mouthpiece  1001  and a cap  1500 . Housing  1040 ′ has a tubular longitudinal channel therein. The channel has an upper open end and a lower open end. The mouthpiece  1001  in needle module  1010 ′ has ink storage grooves  2110  between groove walls  2250  with contact opening  2120 , an opening  2200  with a rectangular profile, and a guide surface  2220 . Needle bundle tip portion  2100  is received in opening  2200  and contacts the guide surface  2220 , under a biasing force as described earlier with regard to needle module  1010 . The ink storage grooves  2110  are separated by a reinforcing wall  2160  and extend from the reinforcing wall  2160  to end surfaces  2230 . 
     As can be appreciated, a needle assembly described herein may be used or adapted to apply other types of liquids to skin. For example, the applied liquid may include colored liquids or pigments, or may include a medicinal or therapeutic agent, collagen, or other like or similar substances. The needle assembly may be used in a liquid applicator for applying the selected liquid. 
     Other features, modifications, and applications of the embodiments described here may be understood by those skilled in the art in view of the disclosure herein. 
     CONCLUDING REMARKS 
     It will be understood that any range of values herein is intended to specifically include any intermediate value or sub-range within the given range, and all such intermediate values and sub-ranges are individually and specifically disclosed. 
     It will also be understood that the word “a” or “an” is intended to mean “one or more” or “at least one”, and any singular form is intended to include plurals herein. 
     It will be further understood that the term “comprise”, including any variation thereof, is intended to be open-ended and means “include, but not limited to,” unless otherwise specifically indicated to the contrary. 
     When a list of items is given herein with an “or” before the last item, any one of the listed items or any suitable combination of two or more of the listed items may be selected and used. 
     Of course, the above described embodiments of the present disclosure are intended to be illustrative only and in no way limiting. The described embodiments are susceptible to many modifications of form, arrangement of parts, details and order of operation. The disclosure, rather, is intended to encompass all such modification within its scope, as defined by the claims.