Flexible MEMS actuated controlled expansion stent

• US 20030040791A1
• Filed: 08/22/2002
• Published: 02/27/2003
• Est. Priority Date: 08/22/2001
• Status: Active Grant

• Current Assignee: Hasan Semih Oktay
• Original Assignee: Hasan Semih Oktay
• Inventors: Oktay, Hasan Semih
• Granted Patent: US 7,097,658 B2
• Time in Patent Office: Days
• US Class Current: 623/1.17
• CPC Class Codes: A61F 2/82 Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents stent-grafts for tubular structures of the body other than blood vessels A61F2/04; stent-grafts for blood vessels A61F2/07; instruments specially adapted for placement or removal of stents or stent-grafts A61F2/95; for closing wounds, or holding wounds closed A61B17/04 - A61B17/115; dilators A61M29/00
• CPC Class Codes: A61F 2/844 folded prior to deployment
• CPC Class Codes: A61F 2/86 Stents in a form characterised by the wire-like elements; Stents in the form characterised by a net-like or mesh-like structure
• CPC Class Codes: A61F 2/92 Stents in the form of a rolled-up sheet expanding after insertion into the vessel , e.g. with a spiral shape in cross-section
• CPC Class Codes: A61F 2220/0075 sutured, ligatured or stitched, retained or tied with a rope, string, thread, wire or cable
• CPC Class Codes: A61F 2230/005 Rosette-shaped, e.g. star-shaped

Abstract

An automatically controlled expansion stent having an expansible stent body, actuation means for expanding the stent body, and control means for actively controlling the actuation means. The stent body is substantially tubular and includes material layers covering a plurality of radial expansion trusses. The stent employs MEMS motors under the control of a programmable logic device to expand the trusses and the stent body. Force from the motor is communicated to the expansion trusses through interconnects, which pivotally connect the trusses and provide channels for pull wires extending from the motors to the trusses. The trusses comprise a plurality of hinged links which produce symmetrical expansion of the stent body when actuated by the MEMS motor.

Claims

1. An automatically controlled expansion stent, comprising:

an expansible stent body;

actuation means for expanding said stent body; and

control means for actively controlling said actuation means.

2. The stent of claim 1, wherein said stent body is substantially tubular and comprises a first and a second end, inner and outer wall surfaces, and a first diameter that permits intraluminal delivery.

3. The stent of claim 2, where said inner and outer wall surfaces each comprise a sheet of material selected from the group consisting of a thin film shape memory alloy, metallic alloy, or thin film polymer.

4. The stent of claim 2, wherein said tubular body is enlarged by the use of at least two radial expansion trusses composed of a plurality of hinged links which allow symmetrical expansion of the radial expansion trusses, and further including a plurality of interconnects interposed between said radial expansion trusses.

5. The stent of claim 4, wherein said hinged links comprise a combination of triangular shaped links, angulated links, and notched angulated links, each attached to an adjoining link by hinged pivot points.

6. The stent of claim 4, wherein said interconnects are arcuate, and wherein said interconnects form a closed cylindrical body when said stent is in a collapsed configuration and are evenly spaced apart when said stent is in a partially expanded or fully expanded configuration.

7. The stent of claim 6, wherein said interconnects each have an interconnect ball joint and shaft at each end and attaches to said radial expansion truss at a socket-shaped pivot point on the radial expansion truss.

8. The stent of claim 4, wherein said expansion trusses are enclosed by inner and outer expansible material layers.

9. The stent of claim 1, wherein said actuation means comprises at least one MicroElectro-Mechanical-System (MEMS) motor operatively connected to said stent body.

10. The stent of claim 9, wherein said control means is electrically connected to said MEMS motors and comprises a device selected from the group consisting of a PLC and a microprocessor.

11. The stent of claim 9, wherein each of said MEMS motors is connected to at least one radial expansion truss through a pull wire extending through at least one of said interconnects which attaches to said radial expansion truss, and wherein as force is exerted on said pull wire by said MEMS motor, said radial expansion truss is expanded.

12. The stent of claim 11, wherein each of said interconnects includes a longitudinal channel running the length of the interconnect through which at least one pull wire may be passed, and further includes an interconnect ball joint having a channel perpendicular to said longitudinal channel which allows a pull wire to be passed down the radius of an associated radial expansion truss to an attachment point.

13. The stent of claim 9, wherein each of said MEMS motors is connected to at least one expansion truss and said MEMS motor turns a beveled drive gear in mesh with a beveled screw gear, each of said gears having intersecting axes, to turn a lead screw passing through a threaded nut at the external circumference of said radial expansion truss and attached to a base at the internal circumference of the radial expansion truss.

14. The stent of claim 9, wherein each of said MEMS motors is connected to at least one expansion truss and said MEMS motors is positioned equidistant between a right handed screw connected to an outer circumference of said radial expansion truss and a left handed screw connected to an inner circumference of said radial expansion truss, and wherein expansion of said truss is achieved when said MEMS motors turns and pull said right handed screw and said left handed screw together.

15. The stent of claim 1, further including a pressure sensor in electrical communication with said control means for detecting forces applied to vascular tissue by said stent.

16. The stent of claim 1, wherein the expansion of said stent occurs radially.

17. The stent of claim 16, wherein said stent has a fully collapsed configuration, a fully expanded configuration, and an infinite number of partially expanded configurations therebetween.

18. The stent of claim 1, wherein said stent body is generally elongate, has an interior surface and an exterior surface, and comprises a coiled sheet of radially overlapping material and said overlapping portion of said body is uncoiled actively through the use of at least one MEMS motor.

19. The stent of claim 18, wherein said stent body includes an interior slot, and wherein said MEMS motor includes a pinion gear in mesh with a rack gear attached to the interior surface of said stent body, said rack gear extending through said slot and centered on the same radial line as the pinion gear and said slot.

20. The stent of claim 18, wherein said exterior surface includes a groove opposing said gear rack on said interior surface, wherein said groove is of a reciprocal shape to said rack gear and allows insertion of said rack gear when said stent is in a coiled or partially coiled configuration, and allows said rack gear to slide in said groove during expansion.

21. The stent of claim 18, further including at least one at least one pressure sensor operatively connected to said MEMS motor.

22. A MEMS-actuated controlled expansion stent for intraluminal delivery, comprising:

a generally tubular stent body defined by a first and a second end and having an inner and outer wall surface, said tubular body having a collapsed configuration, a fully expanded configuration, and wherein said tubular body is capable deforming to assume infinite partially enlarged configurations therebetween;

at least two radial expansion trusses composed of a plurality of hinged links which allow symmetrical expansion of said radial expansion trusses;

a plurality of interconnects interposed between said radial expansion trusses, said trusses and said interconnects forming the superstructure of said tubular body;

at least one Micro Electro Mechanical System (MEMS) operatively connected to at least one of said radial expansion trusses, wherein the MEMS applies force to links in the radial expansion trusses to cause expansion of said trusses;

at least one pressure sensor for monitoring forces exerted on living tissue; and

a programmable logic device in electronic communication with said pressure sensors, wherein said pressure sensor feeds back to said programmable logic device to control the force exerted by the MEMS.

23. The MEMS-actuated controlled expansion stent of claim 22, wherein said first and second ends of said tubular stent body are rounded on the circumference.

24. The MEMS-actuated controlled expansion stent of claim 22, wherein said tubular stent body inner and outer walls are fabricated from a material selected from the group consisting of thin film shape memory alloy, metal alloy, and thin film polymer.

25. The MEMS-actuated controlled expansion stent of claim 22, wherein the tubular element first diameter is representative of the smallest circumference of the tubular element.

26. The MEMS-actuated controlled expansion stent of claim 22, wherein said radial expansion trusses are constructed of a plurality of hinged links.

27. The MEMS-actuated controlled expansion stent of claim 26, wherein said links comprise a combination of triangular shaped links, angulated links, and notched angulated links attached by hinged pivot points.

28. A method of reducing restenosis in vascular tissue when employing a percutaneously introduced prosthetic device, comprising the steps of:

(a) providing an automatically controlled expansion stent having an expansible stent body, actuation means for expanding the stent body;

(b) providing programmable control means for actively controlling the actuation means;

(c) programming the programmable control means to expand the stent body at a predetermined rate and to a predetermined maximum diameter; and

(d) deploying the stent into a patient'"'"'s body using conventional stenting techniques.

29. The method of claim 28, wherein the steps are, in order, a, b, c, and d.

30. The method of claim 28, wherein the stent body is substantially tubular and comprises a first and a second end, inner and outer wall surfaces, and a first diameter that permits intraluminal delivery, and wherein the inner and outer wall surfaces each comprise a sheet of material selected from the group consisting of a thin film shape memory alloy, metallic alloy, or thin film polymer.

31. The method of claim 30, wherein the tubular stent body is enlarged by the use of at least two radial expansion trusses composed of a plurality of hinged links which allow symmetrical expansion of the radial expansion trusses, and further includes a plurality of interconnects interposed between the radial expansion trusses.

32. The method of claim 31 wherein the interconnects are arcuate and form a closed cylindrical body when the stent is in a collapsed configuration and are evenly spaced apart when the stent is in a partially expanded or fully expanded configuration.

33. The method of claim 28, wherein the actuation means comprises at least one Micro-Electro-Mechanical-System (MEMS) motor operatively connected to the stent body.

34. The method of claim 33, wherein the programmable control means is electrically connected to the MEMS motors and comprises a device selected from the group consisting of a PLC and a microprocessor.

35. The method of claim 28, wherein the stent includes at least one pressure sensor in electrical communication with the control means for detecting forces applied to vascular tissue by the stent.

36. The method of claim 28, wherein the stent has a fully collapsed configuration, a fully expanded configuration, and an infinite number of partially expanded configurations therebetween.