Connection method for connecting an isolated micro-conductor

Abstract

The present invention relates to a method for connecting a strand of a multi-strand cable to an electrode of an implantable medical device. The method includes cutting a strand of the multi-strand cable lifting at least one of the free ends, stripping the end of the lifted strand, placing an electrode around the multi-strand cable to partially cover the end of the lifted and stripped stand, and connecting at least one portion of the stripped end of the strand to the electrode.

Claims

1. A method for connecting a strand of a multi-strand cable to an electrode of an implantable medical device, comprising the steps of: cutting the strand of the multi-strand cable to form two free ends at the cut of the strand; lifting at least one of the free ends relative to the rest of the multi-strand cable; at least partially stripping the end of the lifted strand; placing the electrode around the multi-strand cable so as to partially cover the end of the lifted and stripped strand; connecting at least one portion of the stripped end of the strand to the electrode.

2. The method according to claim 1, the method further comprising: covering the other of the free ends of the strand by introducing an insulating sleeve-around the multi-strand cable.

3. The method according to claim 2, the method further comprising: laying at least one of a second sleeve or a polymer glue around the multi-strand cable to control the length of the end of the lifted strand relative to the rest of the multi-strand cable.

4. The method according to claim 1, wherein the cutting comprises at least one of a laser cut, a laser ablation, or the use of a mechanical cutting device.

5. A method for connecting a strand of a multi-strand cable to an electrode of an implantable medical device, comprising the steps of: cutting the strand of the multi-strand cable to form two free ends at the cut of the strand; lifting at least one of the free ends relative to the rest of the multi-strand cable; placing a metal hypotube around the end of the lifted strand so that the metal hypotube is electrically connected to the end of the strand; placing the electrode around the multi-strand cable so as to partially cover the metal hypotube; connecting at least a portion of the metal hypotube to the electrode.

6. The method according to claim 5, wherein the connection is performed by laser welding, crimping or electric welding.

7. The method according to claim 5, further comprising: laying a polymer sheath in order to coat the multi-strand cable and the electrode welded to the multi-strand cable.

8. The method according to claim 5, wherein the electrode is a ring-shaped electrode such that the ring comprises a central hole or a slot configured to perform the welding in step.

9. The method according to claim 5, wherein the electrode is a ring-shaped electrode such that the ring comprises an internal cavity adapted to the dimension of the end of the lifted strand.

10. The method according claim 5, such that the diameter of the strand is between 10 μm and 200 μm, and the diameter of the multi-strand microcable, that is to say the diameter of the entire multi-strand microcable, is less than 0.66 mm and is made from biocompatible materials.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention and its advantages will be explained in more detail in the following by means of preferred embodiments and relying in particular on the accompanying figures, wherein:

(2) FIG. 1 schematically illustrates a microcable in step a) of the method according to the present invention;

(3) FIGS. 2 and 3 schematically illustrate a microcable in step b) of the method according to the present invention;

(4) FIGS. 4 and 5 schematically illustrate a microcable in steps c) and d) of the method according to the present invention;

(5) FIG. 6 schematically illustrates a microcable in step e) of the method according to the present invention;

(6) FIG. 7 schematically illustrates a microcable in step f) of the method according to the present invention;

(7) FIGS. 8a, 8b, 9 and 10 schematically illustrate alternative embodiments of a conductive element;

(8) FIGS. 11a-d schematically illustrate alternative embodiments of the strand to connect.

DETAILED DESCRIPTION

(9) Those skilled in the art will appreciate that the present invention can be applied essentially to any type of connector, particularly to any type of micro-connector configured for implantable devices.

(10) FIG. 1 illustrates a multi-strand microcable 1 whose dimensions are of the order of one micron and which is made from biocompatible materials. The microcable 1 is formed of several strands, each strand being provided with a sheath 1a of insulating polymer. In the process step shown in FIG. 1, one of the strands was laser cut, indicated by the arrow A, so that the strand 2 is provided with two free ends 2a and 2b.

(11) In a variant, the same strand is cut in several places.

(12) In another embodiment, the cutting of the strand 2 is carried out by means of a mechanical device such as micro-knife, pliers, etc.

(13) In the step illustrated in FIG. 2, a portion of length L of the free end 2b of the strand 2 has been lifted and partially extracted from the rest of the microcable 1 so that the axis B of the end 2b of the strand 2 is substantially perpendicular to the axis C of rotation of the cable 1.

(14) The end 2a is not lifted relative to the rest of the microcable 1.

(15) In the step illustrated in FIG. 3, a first insulating sleeve 3, made of polymer material, is inserted, like a ring, around the cable 1 so as to cover the end 2a (which thus becomes not visible on the FIG. 3).

(16) A second sleeve 4, also insulating and of polymeric material, is threaded around the cable 1 so as to cover the portion of the end 2b that has not been extracted in the previous step illustrated by FIG. 2. Thus, this second sleeve 4 ensures that only the length portion L of the end 2b protrudes on the cable 1.

(17) In another embodiment, a polymer adhesive may be used to hold the portion of the end 2b that is not intended to be lifted and partially extracted from the cable 1.

(18) In the embodiment illustrated in FIG. 3, the cable 1 is thus provided with two sleeves 3 and 4 such that the portion of length L of the end 2b projects between the two sleeves 3 and 4.

(19) FIG. 4 illustrates a step wherein a portion 1 of the length portion L of the end 2b is stripped of its polymer insulation 1a by laser ablation. Therefore, the part I of the end 2b corresponds to the conductive portion of the strand 2. A spherical tip 6 is formed at the outermost point of the end 2b. This spherical tip 6, also called “ball tip”, allows to merge, in a kind of ball, the multiple metal strands constituting the strand 2, which prevents individual strands from escaping and thus reduce the reliability of the electrical contact. The spherical tip 6 also provides a larger contact area, further improving the electrical reliability of the contact.

(20) In another embodiment, the insulation of the length L of the end 2b is removed mechanically.

(21) Alternatives to the removal of a portion 1 of the insulating portion 1a and to the formation of a spherical tip 6 at the end of the end 2b are described in FIG. 11.

(22) In FIG. 5, a cylindrical electrode 5 is threaded around the microcable 1 so as to partially cover the sleeve 4 on the opposite side to that of the sleeve 3. The end 2b is arranged so as to be placed on the sleeve 3 such that the axis B of the portion of length L of strand 2 is parallel to the axis C of the cable 1.

(23) In the step illustrated in FIG. 6, the cylindrical electrode 5 is moved to the sleeve 3 so as to cover almost completely the end 2b. Thus, only the spherical tip 6 of the end 2b is not covered by the electrode 5. It is the spherical tip 6 of the strand 2, which corresponds to a conductive part of the strand 2 because it is devoid of polymer insulation 1a, which is then welded to the laser electrode 5. Advantageously, such a weld can be performed with a visual control.

(24) In addition, the method of the present invention makes it possible to avoid the difficulties associated with the presence of polymer in a laser welding, which affects its quality, in particular on a scale of about one micron.

(25) In another embodiment, the cylindrical electrode 5 is crimped in the position shown in FIG. 6 before the welding step, in order to mechanically maintain its position.

(26) In FIG. 7, a polymer sheath 7 is made in order to coat the multi-strand cable 1 and the electrode 5 welded to the cable 1. This sheath can for example be produced by the “reflow” technique, which allows melting the polymer to fill the remaining holes and spaces. This technique makes it possible to obtain an isodiametric finished product and to add an insulating barrier to the assembly.

(27) FIGS. 8a, 8b, 9 and 10 illustrate variants of the electrode 5.

(28) In the variant illustrated in FIGS. 8a and 8b, the electrode 5a is a ring with a central hole 8. In FIG. 8a, the strand 2b isolated from the rest of the cable 1 is aligned with the axis C of the cable 1. In FIG. 8b, the strand 2b is in rotation with respect to the cable 1. However, in both variants, the welding is made at the central hole 8 which is arranged above a portion R of strand 2b.

(29) In FIG. 9, the electrode 5b is a ring with a “U” shape slot 9, also called ring “with frontal loading”. In another embodiment, the slot could be in a “V” shape, an arc shape, etc. In this embodiment, the end of the strand 2b is arranged to be aligned between the longitudinal sides 9 and 10 of the slot 9. The weld is thus made at the slot 9 between the strand 2b and the ring 5b.

(30) In the embodiment of FIG. 10, the electrode 5c is a ring comprising an internal cavity 11. The internal cavity 11 of the ring 5c is adapted to the diameter of the end of the lifted strand 2b. The end of the strand 2b is thus partially housed in the internal cavity 11. This internal cavity 11 makes it possible to leave the space required for the end of the strand 2b to be welded and thus makes it possible to improve the electrical contact surface.

(31) FIG. 11 illustrates alternatives to the formation of a spherical tip 6 for making electrical contact with the conductive member 5, as described above and shown in FIG. 11a.

(32) Thus, in the variant illustrated in FIG. 11b, the end 2b of the strand 2 has been stripped over a length l, and then a hollow metal hypotube 12 has been inserted around the length l stripped of the strand 2. The contact surface between the stripped part 1 and the metallic hypotube 12 ensures electrical contact.

(33) In the variant illustrated in FIG. 11c, the end 2b of the strand 2 is not stripped and therefore still comprises its insulating sheath 1a. A hollow metal hypotube 13 has been inserted around the end 2b and crimped so that the crimping of hypotube 13 is perforating to make an electrical contact with the conductive portion 14 of the strand 2.

(34) The variant of FIG. 11d shows a strand 2 whose end 2b is not stripped and therefore still comprises its insulating sheath 1a. A hollow metal hypotube 13 has been inserted around the end 2b and welded to the end 2b, in particular welded to the conductive portion 14 of the strand 2.

(35) In yet another variant which is not illustrated, the welding can be performed at the two free ends 2a, 2b of the same strand 2 to ensure redundancy of the connection.

(36) In yet another variant which is not illustrated, two opposing strands can be cut, lifted and partially removed from the rest of the cable and welded on both sides.

(37) Finally, in another variant not shown, the separation of the strands of the same cable in a number n sub-cables or wires makes it possible to make the redundancy of welding and thus to improve the reliability of the electrical contact with the conductor element by increasing the number of welds. Especially in the case wherein one of the welds breaks, the n−1 welds make it possible to ensure the electrical contact. Thus, the weld redundancy improves the robustness of the electrical contact.

(38) The embodiments and alternatives discussed above may be combined to form more advantageous alternative embodiments of the present invention.