Note: Descriptions are shown in the official language in which they were submitted.
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This is a division of patent application Serial
No. ~97,637 filed December 13, 1985
The present invention relates -to a unitary me-tal
sheet containing a plurality of surgical needles which
are arranged in a spaced relationship along a plurality
Of continuous rows and are at-tached at the suture
attachment end by breakable connections.
Surgical needles are made, one at a time, by a
multi-step process involving considerable time, labor,
and precision machinery. A brief outline of a typical
process for making surgical needles is the fo]lowing.
Stainless steel wire of the appropriate diameter
is straightened and cut to the desired length to form
a blank. One end of the blank is die-formed and/or
ground to produce a cutting edge or point. The
other end is either drilled to orm a hollow receptable
for a surgical suture, or it is stamped to form a channel
fors~waging the suture. The point is sharpened, and
the needle is bent. As a rule, the final steps are
a heat treatment to temper the needle, that is ! to
increase the hardness without imparting brittleness,
and a polishing process. After this, sutures are
attached to the needles by any of several means. ~ne
additional feature of the prior art process for
making surgical needles is tha-t the shape o~ the
needle is limited by what can be done to a piece of
wire. ~s will be apparent below, this inventlon
provides a process that can be used to make any shape
that can be drawn in two dimensions.
The multi-s-tep process is acceptable for the
production of relativel~ large surgical needles,
but with the advent of microsurgery and the need for
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ever smaller surgical needles, the process has proven
to be quite inefficient for the production of small
needles having diameters of, e.g., from one to three
mils because of the large amount of skilled labor and
precision machinery required in handling such small
needles individually throughout the various steps of
the process leading to attachment of sutures and final
inspection.
This invention provides a process tha-t is parti-
cularly well adapted to the efficient simultaneous
production of large numbers of small size surgical
needles.
According to a broad aspect of the present
invention, there is provided a unitary metal sheet
formed from a single sheet of metal containing
a plurality of surgical needles. Each needles has
a pointed end and a suture attachment end. The
needles are arranged in spaced relationship along
a plurality of continuous rows and are attached
at the suture attachmen-t end by breakable connections
to base rows that extend substantlally across the
width of the sheet~
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The Pr ior Art
~eath, in U.~. Patent No. 2,735,763, ~iscloses a photo-
etching process for makinq small parts from a sheet of
thin metal which will not withstand any mechanical
working.
Jacks et al., in U.SO Patent No. 3,35R,363, discloses a
photoetching process for making fuse elements.
Snyder, in U.S. Patent No. 3,816,273, discloses a photo-
etching process for making wire.
Poler, in U.S. Patent No. 4,080t709, discloses a photo-
etching process for making the mounting structure for an
intra-ocular lens.
ninardo~ in ~.S. Patent No. 4,282,311, and James, in
U.~. Patent No. 4,2~4,712, disclose a photoetching process
for making flylea~s for video flisc styli.
nrief nescription ~
Fi~. 1 is a top plan view of a metal sheet containing a
plurality of surgical needles produced by the process of
the invention;
Fig. 2 i~ an enlargcment o a portion of the shee~ of
Fig. 1;
Fig. 3 is an enlarged perspective view of a surgical
needle made by the process of ~he invention;
Fig. 4 is a perspective view of the needle of Fig. 3
attached to a surgical suture;
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Fig. 5 is an enlar~ed plan view of a photomask of the
image of a single surgical nee~le that can be used in
carrying out the process of the invention;
Fig. 6 is an enlarged plan view of a second photomask of
the image of a single surgical needle that can be used in
carrying out the process of the invention;
Fig. 7 is an enlarged view of a portion of ~ig. 5;
Fig. 8 is an enlarged perspective view of the suture
attachment end of the needle of Fig. 3;
Fig. 9 is a cross-sectional view ~aken along line 9-9 of
Fig. 8, and a~ditionally showlng a suture ~ttached to the
needle;
Eig. lO is an enlarged view of a portion of Fig. 2;
Fig. ll is a cross-sectional elevation taken along line
ll-ll of Fig. 10; an~
Eig. 12 is an enlargement of a portion of Fig. 5.
~ f the Invention
The first step in the process of the invention is to coat
at least one side of a metal sheet with a light sensitive
photore6ist material. The metal sheet that is used can be
selectefl so as to possess all o the strength, hardness,
tuughness, and grain structure, in the sheet form that the
metal will need in the form of a surgical needle. This is
one advantage over the current multi-step process for
producing surgical needles, in which one step is usually a
3~ heat treatment step to develop optimum properties. Any
metal or allo~ that can be obtained in thin sheet form can
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be used, provided that it has the re~uisite properties of
strength, hardness, etc. ~or instance, a tensile strength
of at lea~st ahout 300 ,oon psi, a Rockwell C hardness of at
least 45, and ductility so that the needle can be bent up
to about 90 and then straightened without breaking, are
desirable. The metals that can be used include stainless
steel, specifically, 3Z0 stainless steel and ~in 5 and ~,in
6 razor blade grade stainless steel, and molybdenum. Gin
6 stainless steel is preferred. The metal sheet will
ln usually have a thickness of from about one to about ten
mils.
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The photoresist compositions used are known in the art.
For instance, they are discussed in "Photo-Resist Mate-
rials and Processes" by ~illiam DeForest, McGraw-~ill
1975, and a wide variety of photoreslst compositions are
available commercially~ The metal sheet can be coated
with the photoresist by any convenient method, such as flip
coating, spraying, and the like. In a preferred aspect of
the invention, both sides of the sheet are coated with the
photoresist an~ the needle images are formed on both
sides. (In any event, the second side must be coatecl with
either a photoreslst or a protective coating.) In a
typical coating process, the metal sheet is thorou~hly
cleaned, rinsed, dipped in dilute aqueous acid, e.g., 10%
HCl, rinse~ again, dried, and then c~ated. Since the
photoresist compositions are sensitive to light/ the
coating should be carried out under "safe light" condi-
tions, e.g., under yellow or orange light, or in the dark.
3n After coating, the coated metal sheet is baked at a
moderately elevated temperature for a few minutes, e.g.,
at about ~n oc . for about ln minute5, to dry the coating
After the coated sheet has cooled, it is then exposed to
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light in the image of a plurality of surgical needles,
shaped to compensate for lateral etching of metal during
the etching step, a principle that is well understood in
the art. This is done hy first covering the coated sheet
with a negative or first photomask containing an image of
the needles. An illustrative enlarged negative or first
photomask of a single surgical needle is shown as 14 in
Fig. 5 (it will be discussefl in more detail) below. In a
preferred aspect of the invention, the coated reverse side
of the metal sheet is then covered with a second photomask
that is the mirror image of the first photomask 14 and in
perfect register therewith, and then exposed to light. An
illustrative enlarged second photomask of a single surgi-
cal nee~le is shown as 16 in Fig. 6~ As will be explaine~
in more detail below, the said second photomask 1~ may
differ in certain details from the said first photomask
14. The light source used to expose the photoresist is
rich in ultraviolet ra~iation. A carbon-arc light is
preferred, but ~ercury-vapor lamps o~ ultraviolet rich
fluorescent lights may also ~e usefl. Typical exposure
times are within the range of a few seconds to several
minutes, ~epen~ing u~on the nature and power o~ the light
source, the distance of the light from the photoresist,
and the sensitivity of the photoresist. The lnstruction~
of the manu~acturer of the photoresist~should be followed
in this respect.
After exposure, the photoresist is rinsed in a suitable
commercially available "developer" formulate~ for the
particular photoresist being used, to remove the unexposed
photoresist. After Yinsing~ the sheet with the
photoresist coating in the form o~ surgical neeflles may be
~aked at, e.g., 120 to ~fiOC. for 5 to 1~ minutes to
fu~ther harden the remaining photoresist coating. The
next step is to etch away the unwant d metal in an etching
solution. Typical etching solutions include 36- to 42-
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degrees Baum~ a~ueous ferric chloride, an a~eous mixture
of ferric chlori~e and HCl, or a mixture of aqueous
hydrochloric acid and nitric acid, or the like. ~uch
etching so~utions are known in the art, as is their use in
a photoetching process. After the etching step, there
remains the desired surgical needles, which are removed
from the etching solution, washed, and dried. The
developed and hardened photoresist is then removed by
dissolving away with a suitable co~mercially available
stripper forMulated for the photoresist being used. A
detailed ~iscussion of the application of the above
process to a specific surgical needle design follows~
A surgical needle to be produced hy the process of the
invention is shown as 12 in Fig. 3~ The needle inclu~es a
shank 18, a point 20, and a suture attachment end 22. In
this Aesign, the suture attachment en~ 2 includes a
channel 24 ~y which a suture 26 may be attached, as is
explained in more detail below. The first step in using
the process of the invention to produce this needle 12 is
to make a precision black ~rawing of the neeflle 12 several
hundre~ times larger than the re~uired finished siæe.
This drawing is then optically reduced to the required
size, and an exposure is ma~e near the corner of a sheet
of high resolution film. The film is moved laterally by a
precision stepping device and a second exposure is made.
This is repeated until a row of exposures across the film
is completed. The stepping device moves the film upward
by one rowls wi~th, an~ a second row of exposures is made~
This process i~ repeatefl until the entire film area ls
coverefl. The film is then developed to produce a negative
or photomask of the images of the needles.
Fig. 1 shows a sheet ~8 containing a plurali~y of surgical
needles 1~ attached at their suture attachmen~ ends ?.2 to
- continuous base rows 30 that extend the width of the sheet
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2R. An enlarge~ent of a portion of the ~heet 2~ showing
one needle 12 is shown in Fig. 2. An enlargement of a
~hotomask 14 corresponding to this needle 12 is shown in
~ig. 5. The di~ensions of the image 12a of the needle in
the photomask are ~odified to allow for lateral etching of
the metal during the etching step. The photomask image of
a particular part will be referred to by the same
reference number, with the addition of an "a" to the
num~er. Thus, the photomask image of the needle 12 is
1~ referred to by the reference number 12a.
As a first approximation, the metal will be etched
lat~rally about the same distance as vertically. Thus, ln
the preferred situation wherein the ~etal sheet is etched
1~ from both sides, lateral undercutting equal to approxi-
mately one-half the thickness of the sheet should be
allowed for in the photomask. The image 2na of the
nee~le's point in the photomask preferahly ~oes not come
to a point, but rather is preferably hluntefl as is shown
in Fig. 5. Lateral etching will cause a point to be
formed. This is shown schematically in Fig. 7~ which is
an enlar~e~ent of the image 20a of the needle's point.
The arrows show the directlon o~ lateral etching of the
metal so that, after the etchin~ step, the point of the
2~ nee~le will have the configuration shown in dashed lines
in Fig. 7. (If the needle's point were pointed in the
photomask, aEter etching, the point would probably be
rounfleA rather than sharply pointed, as a resul~ o~ the
lateral etching.)
3~
For ease of handling the needles produced hy the process
of the invention, it i5 preferred to prodllce the needles
such that they are attached by a breaka~le connection to
the metal sheet ~rom which they are etched. ~y so doing,
3~ the needles can ~e kept separated and in order until they
are ready for ~urther processing. One way to do this is
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illustrated in the drawings (see, especially, Figs. 1, ~,
5, and 6). The sheet 28 shown in Fig. 1 has the needles
12 attached to base rows 30 that extend all the way across-
the sheet. To assist in the removal of the individual
needles 12 from the base rows 30, a transverse groove 32
may be made at the point of attachment of the needle 1~. to
the base row 3~ See Figs. 10, 11 and 1~.) In the
photomask 14, the groove 32 is provided for by a
transverse line ~2a, in one of the two photomasks only, at
the point of attach~ent to the base row 30a.
Reerring now to ~igs, 5, 6, ~, and ~, the suture attach-
ment en~ 2~ includes a channel 24 for use in attaching the
needle to a suture 2~. In the embodiment shown, the
channel ~4 is a bilevel channel in which the first half 34
of the channel is offset longitudinally from the second
half 36, as is shown clearly in Figs. 8 and 9. The two
halves of the channel are etched equally from both sides
of the metal sheet so that each has a depth of about one
half the thickness of the sheet. Where the two halves 34,
36 overlap, a hole 3~ is pro~uced so that the two halves
34, 36 com~unicate with each other. A suture 26 is
atkachefl by ~illing both halves 34, 3h with an adheslve
material (not shown) such as an epoxy glue while the
~5 second half 36 is lying on a flat surface, and then
inserting the end of a suture 2fi through the hole 38
hetween the two halves, 34, 36 as ls shown in ~ig. 9. The
epoxy resin is kardened at roo~ temperature, and then
given a final cure in an oven at moderately elevated
temperatures, such as 40~ to 6noc. The photomask images
34a, 36a, of the two halves of the channel are thin lines,
as is shown in ~igs. 5 an~ 6, to allow for the lateral
etching that will occur during the etching process. The
"bilevel" channel desc~ibed here has several advantageous
properties. ~irst, it serves to hold the suture securely
in place while the adhesive sets, and, second, it helps to
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prevent the suture from being pulled out of the channel hy
a lateral force.
The needles 12 may be detached from the sheet 28 before
attaching to a suture 26. This can be ~one by grasping a
single needle 12 with forceps and flexing it at the break-
off groove 32. Alternatively, all neeflles in a single row
can be detached simultaneously by cutting both ends of the
base row 3n, removing it from the sheet 28, and then
pressing the row of nee~les lightly on to an a~hesive
surface. Flexing the base row 3~ upwards will cause it to
break off at the break-off grooves 32, leaving the neeAles
precisely spaced and securely held on the adhesive surface
in an ideal position for suture attachment.
After the etching step and after removal of the hardened
photosistj if des-red, entire sheets of neeflles may be
electropolished using conventional electropolishing
methods to smooth off rough edges, polish the surfaces,
2n and improve the shape of the needle points hy reducing or
eliminating undesirahle projections, and hy sharpening the
edge. This is another advanta~e of the invention, since
hundreds, and perhaps thousands, of needles can he
electropoli~hed simultaneously in a Eew minutes.
A typical electropolishing bath is an a~ueous sul~uric,
phosphoric, and glycolic aci~ bath. Polishing times of
about 30 seconds at ten volts and ~noc. are typical.
The invention has heen described and claimed in terms o~ a
dry positive photoresist technique, that is, the hardened
photoresist on the metal sheet is in the image of the part
- that is to be made. It is theoretically possible to use a
wet photoresist or a negative phokoresist technique in
carrying out the process of the invention, although to do
so would be awkward and uneconomical.
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