Patent Grant
8915769
This application is the U.S. National Phase under 35 U.S.C. §371 of International Application No. PCT/JP2010/052376, filed on Feb. 17, 2010, which in turn claims the benefit of Japanese Application No. 2009-034489, filed on Feb. 17, 2009, the disclosures of which Applications are incorporated by reference herein.
The present invention relates to a method of manufacturing a tubular structure and a stent. In particular, the present invention relates to a method of manufacturing a tubular structure by housing a tubular base, which has a side circumference surface formed in a bellows-like shape, in a polishing container and by polishing the surface of the housed tubular base with magnetic particles and abrasive particles. The present invention also relates to a stent that is manufactured by this method.
A stent, which is also generally called a lumen expanding device, is a medical device that is formed by performing a polishing process, such as magnetic polishing, on a stent base that is formed such that a tubular body, which is made of material having high expansive force and high restoring properties, is subjected to laser cutting so that incisions are made on a side circumference surface of the tubular body in order that expansive force is given in a radially outward direction and whereby the side circumference surface is formed into a bellows-like shape.
Such a stent is mounted in a compressed manner, for example, inside a catheter or on a balloon at the tip of a catheter so that a diameter of the stent becomes tapered. When the catheter reaches a constriction region in a blood vessel, the stent is pushed out from the tip of the catheter, expands together with the constriction region in the blood vessel due to the self-restoring property or by the balloon at the tip of the catheter, and remains placed at this region.
Meanwhile, the following method has been known as an example of the above-mentioned magnetic polishing method. For example, there is a method of manufacturing a stent by housing a stent base in a polishing container; causing magnetic particles, which are formed of a magnetic substance and sealed inside the polishing container, to flow along a circumferential direction of the stent base due to the action of magnetic poles arranged outside the polishing container; and supplying abrasive particles, which are formed of a non-magnetic substance, along an axial direction of the stent base from an external supply source, thereby polishing a surface of the stent base. According to the above method, it is possible to polish the surface of the stent base in a good state and to manufacture a stent with good surface smoothness (see, for example, Patent Literature 1).
However, in the method proposed in the above-mentioned Patent Literature 1, because the surface of the stent base that is exposed inside the polishing container is polished with the magnetic particles and the abrasive particles, the entire surface of a stent 200 is approximately uniformly polished as illustrated in
The present invention has been made in view of the above, and it is an object of the present invention to provide a method of manufacturing a tubular structure capable of appropriately polishing a surface of a tubular structure and performing microfabrication for changing a shape of a structural region of the tubular structure, and to provide a stent.
According to one aspect, there is provided a method of manufacturing a tubular structure by housing a tubular base, which has a side circumference surface formed in a bellows-like shape, in a polishing container, causing magnetic particles formed of a magnetic substance to flow along a circumferential direction of the tubular base due to action of magnetic poles arranged outside the polishing container, and supplying abrasive particles formed of a non-magnetic substance to the polishing container by a supplying means arranged outside the polishing container so that the abrasive particles flow along an axial direction of the tubular base, thereby polishing a surface of the tubular base, the method including: a first polishing step of polishing an exposed surface of the tubular base by causing the magnetic particles and the abrasive particles to flow while an inner surface of the tubular base remains covered; and a second polishing step of polishing an exposed surface of the tubular base by causing the magnetic particles and the abrasive particles to flow while an outer surface of the tubular base remains covered.
In the method, a polishing condition may be changed between the first polishing step and the second polishing step.
In the method, a process time may be changed between the first polishing step and the second polishing step.
In the method, magnitude of magnetic force may be changed between the first polishing process and the second polishing process.
In the method, a process time of the second polishing step may be longer than a process time of the first polishing step.
In the method, each of the first polishing step and the second polishing step may include a step of moving at least one of the magnetic poles and the polishing container while the magnetic poles are relatively displaced with respect to the tubular base along the axial direction of the tubular base.
In the method, at each of the first polishing step and the second polishing step, a time taken to polish end portions of the tubular base by moving the magnetic poles to positions corresponding to the end portions may be longer than a time taken to polish a central portion of the tubular base by moving the magnetic poles to a position corresponding to the central portion.
According to another aspect, a stent is manufactured by the above-mentioned method.
According to the present invention, there includes a first polishing process, in which an exposed surface of a tubular base is polished by causing magnetic particles and abrasive particles to flow while an inner surface of the tubular base remains covered, and a second polishing process, in which an exposed surface of the tubular base is polished by causing the magnetic particles and abrasive particles to flow while an outer surface of the tubular base remains covered. Therefore, by adjusting a time required for the first polishing process and a time required for the second polishing process, or by adjusting a region to be polished in the first polishing process and a region to be polished in the second polishing process, it is possible to polish the surface of the tubular structure in a good state and it is also possible to perform microfabrication for changing a shape of a structural region of the tubular structure.
Preferred embodiments of a method of manufacturing a tubular structure and a stent according to the present invention will be explained in detail below with reference to the accompanying drawings. In the following embodiments, a stent will be explained as an example of the tubular structure.
The abrasive particle tank 2 stores therein abrasive particles 6. More specifically, the abrasive particles 6 in the form of slurry, which is a mixture of diamond, aluminum oxide, or silicon nitride in oil, are accumulated in the abrasive particle tank.
The pump 3 is a supplying means that sucks in and discharges the abrasive particles 6, which are in the form of slurry and accumulated in the abrasive particle tank 2, in order to circulate the abrasive particles 6 through the polishing container 4 and the abrasive particle tank 2 in turn via the pipe 5 as indicated by arrows in
The polishing container 4 is a cylindrical container with openings at both ends. The openings are connected to the pipe 5. A stent base (a tubular base) 10 is fixedly supported inside the polishing container 4. The stent base 10 is formed such that a tubular body, which is made of flexible material having restoring force, such as stainless steel, cobalt-chrome (Co—Cr) alloy, or titanium nickel (Ti—Ni) alloy, is subjected to laser cutting so that incisions are made on a side circumference surface of the tubular body in order that expansive force is given in a radially outward direction and whereby the side circumference surface is formed into a bellows-like shape.
Magnetic particles 7 formed of a magnetic substance, such as iron, nickel, or specially-treated stainless, are sealed inside the polishing container 4. The polishing container 4 is rotatable around a shaft center on the assumption that a central axis of the polishing container functions as the shaft center, though not illustrated.
Magnetic poles 8 as magnetic-force generation sources are arranged outside the polishing container 4. The magnetic poles 8 are arranged such that portions of the magnetic poles 8 face each other across the polishing container 4 and have opposite polarities. The magnetic poles 8 are slidable along an axial direction of the polishing container 4, though not illustrated. As the magnetic-force generation source, a permanent magnet or an electromagnet may be applied, and the magnitude of the magnetic force can be changed appropriately.
With use of the polishing apparatus 1, a stent 20 (see
After the stent base 10 is fixedly supported as above, the polishing container 4 is rotated around the shaft center of the polishing container 4, and at the same time, the pump 3 is activated. Accordingly, the magnetic particles 7 and the abrasive particles 6 that are in the form of slurry and carried between the magnetic particles 7 are caused to flow through and polish a predetermined region of an exposed surface of the stent base 10 (a first polishing process). At this time, the magnetic poles 8 are slightly reciprocated along the axial direction of the polishing container 4, so that the exposed surface of the stent base 10 can be effectively polished.
After the predetermined region is polished, the magnetic poles 8 are moved along the axial direction of the polishing container 4, that is, the magnetic poles 8 are moved along the axial direction of the stent base 10 so as to be relatively displaced with respect to the stent base 10, and the polishing container 4 is again rotated around the shaft center of the polishing container 4 while the pump 3 is again activated, so that another region of the exposed surface of the stent base 10 is polished. At this time, the magnetic poles 8 are again slightly reciprocated along the axial direction of the polishing container 4, so that the exposed surface of the stent base 10 can be effectively polished.
After the above operation is repeated and polishing of the exposed surface of the stent base 10 with the inner surface remaining covered is completed, the pump 3 is deactivated and the rotation of the polishing container 4 is stopped.
Thereafter, as illustrated in
After the stent base 10 is fixedly supported as above, the polishing container 4 is rotated around the shaft center of the polishing container 4, and at the same time, the pump 3 is activated. Accordingly, the magnetic particles 7 and the abrasive particles 6 that are in the form of slurry and carried between the magnetic particles 7 are caused to flow through and polish a predetermined region of an exposed surface of the stent base 10 (a second polishing process). At this time, the magnetic poles 8 are slightly reciprocated along the axial direction of the polishing container 4, so that the exposed surface of the stent base 10 can be efficiently polished. In particular, it is preferable that a process time of the second polishing process should be longer (more specifically, approximately twice longer) than that of the first polishing process.
After the predetermined region is polished, the magnetic poles 8 are moved along the axial direction of the polishing container 4, that is, the magnetic poles 8 are moved along the axial direction of the stent base 10 so as to be relatively displaced with respect to the stent base 10, and the polishing container 4 is again rotated around the shaft center of the polishing container 4 while the pump 3 is again activated, so that another region of the exposed surface of the stent base 10 is polished. At this time, the magnetic poles 8 are again slightly reciprocated along the axial direction of the polishing container 4, so that the exposed surface of the stent base 10 can be effectively polished.
After the above operation is repeated and polishing of the exposed surface of the stent base 10 with the outer surface remaining covered is completed, the pump 3 is deactivated and the rotation of the polishing container 4 is stopped. As a result, the stent 20 is manufactured.
According to the above manufacturing method, there includes the first polishing process, in which the exposed surface of the stent base 10 is polished by causing the magnetic particles 7 and the abrasive particles 6 to flow while the inner surface of the stent base 10 remains covered, and the second polishing process, in which the exposed surface of the stent base 10 is polished by causing the magnetic particles 7 and the abrasive particles 6 to flow while the outer surface of the stent base 10 remains covered. Therefore, by adjusting a time required for the first polishing process and a time required for the second polishing process, or by adjusting a region to be polished by the first polishing process and a region to be polished by the second polishing process, it is possible to polish the surface of the stent 20 in a good state and it is also possible to perform microfabrication for changing the shape of a structural region of the stent 20.
In particular, if the process time of the second polishing process is longer (approximately twice longer) than that of the first polishing process, the outer surface of a strut portion 21 of the stent 20 can be larger than the inner surface of the strut portion as illustrated in
Furthermore, because each of the first polishing process and the second polishing process described above includes a process of moving the magnetic poles 8 along the axial direction of the polishing container 4, a cross-sectional area of the stent 20 can be appropriately adjusted by changing a polishing time for each region to be polished, as illustrated in
The preferred embodiments of the present invention are explained above; however, the present invention is not limited to the above embodiments and various modifications may be made. For example, although the polishing container 4 rotates around the shaft center of the polishing container 4 in the above embodiment, according to the present invention, the magnetic poles may rotate around the central axis of the polishing container.
Furthermore, the above embodiment has been explained with an example in which the magnetic poles 8 are slightly reciprocated along the axial direction of the polishing container 4 in the first polishing process and the second polishing process; however, according to the present invention, the polishing container itself may be reciprocated, that is, oscillated, along the own axial direction.
Moreover, the magnetic poles 8 are slidable along the axial direction of the polishing container 4 in the above embodiment; however, according to the present invention, the polishing container may slide along the axial direction of the polishing container while the magnetic poles are relatively displaced with respect to a tubular base along the axial direction of the tubular base.
Furthermore, the process time of the second polishing process is longer than that of the first polishing process in the above embodiment; however, according to the present invention, the magnetic force may be appropriately changed in each polishing process.
As described above, the method of manufacturing the tubular structure according to the present invention is useful in manufacturing a tubular structure having a complicated shape, such as a stent.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-034489 | Feb 2009 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2010/052376 | 2/17/2010 | WO | 00 | 8/17/2011 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2010/095664 | 8/26/2010 | WO | A |
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| Entry |
|---|
| Decision of Patent Grant of JP 2011-500637 dated Nov. 19, 2013 with English translation. |
| Number | Date | Country | |
|---|---|---|---|
| 20110301691 A1 | Dec 2011 | US |
