Laser system and processing conditions for manufacturing bioabsorbable stents

Patent metadata

Field	Value
Publication number	US-9744625-B2
Application number	US-201615200876-A
Country	US
Kind code	B2
Filing date	Jul 1, 2016
Priority date	Jun 10, 2010
Publication date	Aug 29, 2017
Grant date	Aug 29, 2017

Abstract

The present invention involves laser machining polymer substrates to form a stent with laser parameters that minimize damage to the substrate in a surface region adjacent to the machined edge surface. The wavelength and pulse width are selected for this unique application and they can be controlled to minimize the surface modifications (such as voids, cracks which are induced by the laser-material interaction) which contribute to the variation in mechanical properties with distance from the edge surface, bulk mechanical properties, or a combination thereof.

First claim

What is claimed is:

1. A method of laser machining a substrate to form a stent, comprising:
providing a thin-walled polymer substrate;
laser machining the thin-walled polymer substrate with a laser beam with a pulse width and wavelength that cuts through the wall to form structural elements having a machined edge surface,
wherein the laser beam modifies the substrate in a surface region adjacent to the machined edge surface,
wherein the modifications include voids, cracks, variation in modulus of the polymer with distance from the edge surface, or a combination thereof, and characterized by an average laser power per pulse of the laser beam being 0.5-4 W, and by
selecting the pulse width and wavelength so that the voids or cracks are present at no greater than a depth of 2 microns or the modulus converges at no greater than 4 microns.

2. The method of claim 1 , wherein the polymer is poly(L-lactide) (PLLA) or poly(L-lactide-co-glycolide) (PLGA).

3. The method of claim 1 , wherein the polymer is PLLA and the wavelength is 532 nm and the pulse width is less than or equal to 10 ps and greater than or equal to 1 ps and the average laser power is 1.5-3.0 W.

4. The method of claim 1 , wherein a repetition rate of the laser beam is 80-100 kHz.

5. The method of claim 1 , wherein the selected pulse width and wavelength of the laser beam minimize damage to the surface region adjacent to the machined edge surface arising from thermal and nonthermal ablation,
wherein the minimized damage comprises of the cracks or voids which arise from nonthermal ablation and melting arising from thermal ablation.

6. The method of claim 1 , wherein the polymer is PLLA and the wavelength and the pulse width are adjusted to within the green range and to 1-10 ps and the average laser power is 1.5-3.0 W.

7. The method of claim 1 , further directing a cooling gas at a region of the substrate machined by the laser beam.

8. The method of claim 6 , wherein the laser beam causes variation in modulus of the polymer with distance from the edge surface, wherein the modulus converges at a distance less than 10 microns when the wavelength of the laser beam is within the green range.

9. A method of laser machining a substrate to form a stent, comprising:
providing a thin-walled polymer substrate;
laser machining the thin-walled polymer substrate with a laser beam with a pulse width and wavelength that cuts through the wall to form structural elements having a machined edge surface,
wherein the laser beam modifies the substrate in a surface region adjacent to the machined edge surface,
wherein the modifications include voids, cracks, variation in modulus of the polymer with distance from the edge surface, or a combination thereof, and characterized by
selecting the pulse width and wavelength so that the voids are present at a depth of 1-2 microns.

10. The method of claim 9 , wherein the polymer is PLLA or PLGA.

11. The method of claim 9 , wherein the polymer is PLLA and the wavelength is 532 nm and the pulse width is less than or equal to 10 ps and greater than or equal to 1 ps.

12. The method of claim 9 , wherein the repetition rate is 80-100 kHz.

13. The method of claim 9 , wherein the selected pulse width and wavelength of the laser beam minimize damage to the surface region adjacent to the machined edge surface arising from thermal and nonthermal ablation,
wherein the minimized damage comprises of the cracks or voids which arise from nonthermal ablation and melting arising from thermal ablation.

14. The method of claim 9 , wherein the polymer is PLLA and the wavelength and the pulse width are adjusted to within the green range and to 1-10 ps.

15. The method of claim 9 , further directing a cooling gas at a region of the substrate machined by the laser beam.

16. The method of claim 14 , wherein the laser beam causes variation in modulus of the polymer with distance from the edge surface, wherein the modulus converges at a distance less than 10 microns when the wavelength of the laser beam is within the green range.

Assignees

• Abbott Cardiovascular Systems Inc

Inventors

• Harrington Joel
• Vaughan Ryan
• Jow Kevin
• Pippey William
• Chen Yung-Ming

Classifications

• B23K2103/50

  Inorganic materials other than metals or composite materials · CPC title

• B23K26/0624

  using ultrashort pulses, i.e. pulses of 1 ns or less · CPC title

• B23K26/402 Primary

  involving non-metallic material, e.g. isolators · CPC title

• A61F2240/001

  Designing or manufacturing processes · CPC title

• B23K26/50

  Working by transmitting the laser beam through or within the workpiece · CPC title