MEDICAL PRODUCT AND METHOD FOR PRODUCING A PRODUCT, IN PARTICULAR A MEDICAL PRODUCT

Abstract

A medical device, more particularly a balloon catheter, includes at least one multilayer structure with at least one metal layer and at least one elastomer material layer. A process is used to produce a product, such as the medical device.

Claims

1. A medical device having at least one multilayer structure comprising: at least one metal layer; and at least one elastomer material layer.

2. The medical device according to claim 1, wherein the at least one elastomer material layer comprises an elastomer material selected from the group consisting of elastomers, thermoplastic elastomers, thermoplastic polyamide elastomers, thermoplastic copolyester elastomers, olefin-based thermoplastic elastomers, thermoplastic styrene block copolymers, urethane-based thermoplastic elastomers, olefin-based thermoplastic vulcanizates, olefin-based crosslinked thermoplastic elastomers, natural rubber vulcanizates, synthetic rubber vulcanizates, styrene-butadiene rubber, butadiene rubber, acrylonitrile-butadiene rubber, butyl rubber, ethylene-propylene-diene rubber, chloroprene rubber, polyisoprene rubber, polyalkylsiloxanes, polydimethylsiloxane, silicone rubbers, silicone elastomers, methyl silicone, vinyl methyl silicone, phenyl vinyl methyl silicone, phenyl-modified silicone, fluoroalkyl silicone, fluoro vinyl methyl silicone, and mixtures of at least two of the aforementioned elastomer materials.

3. The medical device ccording to claim 1, wherein the at least one metal layer includes at least one metal, selected from the group consisting of gold, platinum, indium, tin, copper, silver, gallium and alloys of at least two of the aforementioned metals.

4. The medical device according to claim 1, wherein the at least one elastomer material layer has a layer thickness of 0.0001 mm to 0.2 mm, and the at least one metal layer has a layer thickness of 150 nm.

5. The medical device according to claim 1, wherein the at least one metal layer directly covers the at least one elastomer material layer.

6. The medical device according to claim 1, wherein at least one adhesion layer is formed between the at least one metal layer and the at least one elastomer material layer.

7. The medical device according to claim 6, wherein the at least one metal layer covers the at least one adhesion layer directly and completely and the at least one adhesion layer covers the at least one elastomer material layer directly and only in regions.

8. The medical device according to claim 6, wherein the at least one adhesion layer includes at least one material selected from the group consisting of titanium, aluminum, chromium, and mixtures of at least two of the aforementioned materials.

9. The medical device according to claim 1, wherein the at least one multilayer structure further includes at least one additional elastomer material layer that directly covers the at least one metal layer.

10. The medical device according to claim 1, wherein the at least one multilayer structure or the at least one metal layer has a varying surface morphology.

11. The medical device according to claim 1, wherein the at least one multilayer structure forms part of a surface of the medical device or is integrated in a wall of the medical device.

12. The medical device according to claim 1, wherein the medical device is curved.

13. The medical device according to claim 1, wherein the medical device comprises a balloon catheter having a balloon that includes the at least one multilayer structure.

14. The medical device according to claim 1, wherein the at least one multilayer structure defines a sensor unit of the medical device.

15. A process for producing the medical device according to claim 1, the process comprising the steps of: a) producing the at least one multilayer structure; and b) transferring the at least one multilayer structure to a substrate, with formation of the substrate provided with the at least one multilayer structure.

16. A multilayer structure comprising: at least one metal layers; and at least one elastomer material layer.

17. The multilayer structure according to claim 16, wherein the multilayer structure comprises a sensor unit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0119] FIG. 1 shows an example of a functionalized metal-polymer multilayer composite structure.

[0120] FIG. 2 shows principal steps in a process.

[0121] FIG. 3 shows a process of transfer to a cylindrical PDMS base substrate.

[0122] FIG. 4 shows a finished PDMS cylinder with integrated sensor structures.

[0123] FIG. 5 shows a selected morphology region of a prepared specimen in relevant steps of an operation.

DETAILED DESCRIPTION

Examples Section

1. Experimental Methods

1.1 MPBC Sample Design

[0124] Metal-polymer multilayer composites, more particularly metal-polymer bilayer composites (MPBC), having a thin (approx. 100 m) polydimethylsiloxane membrane (PDMS membrane) functionalized with structured 40 nm layers of Au were used. Two different structuring methods were used, one using conventional photolithographic processing and the other using an aperture mask. The Au metalization makes it possible for there to be stretch-sensitive regions and regions containing leads in which the resistance of said regions changes only slightly under stress. The leads here comprise self-similar serpentine structures. The sensor region employs a stretch-sensitive surface with microcracks. An example of a functionalized metal-polymer multilayer composite structure is shown in FIG. 1.

1.2 Substrate Preparation

[0125] The principal steps in the process are shown in FIG. 2. 4-inch wafers 1 polished on one side and having a thickness of 0.5 mm were used as a handling platform. A UV-sensitive dicing film 2 (also known as a saw film) made of polyethylene terephthalate (PET) (Adwill D-203, 50 m) was transferred onto the wafer 1 with a soft foam roller 3. The applied film 2 was cut with a scalpel along the wafer edges and then exposed to UV light 4 to reduce adhesion to the wafer 1 (special device having 5 Ster-L-Ray low-pressure mercury lamps). At a minimum dose of about 160 mJ/cm.sup.2, adhesion decreases to about 1% of its original value (according to the data sheet from 772.2 N/m to 5.8 N/m). To ensure a uniform and maximum reduction in adhesion, the UV activation was performed at an increased dose of about 250 mJ/cm.sup.2 and was carried out under a nitrogen atmosphere to prevent ozone formation. After the UV treatment, a degassed, bubble-free PDMS prepolymer 5 (Elastomer kit marketed under the registered trademark SYLGARD 184, mixture 10:1 (base to curing agent), mixed using a Thinky 250-ARE planetary centrifugal mixer) was applied onto the handling wafer 1 covered with the film 2 by spin coating at 600 rpm (acceleration 200 rpm/s) for 60 sec. A vacuum was then applied (10 min) to ensure a defect-free and even membrane, before it was cured in an oven at 90 C. for 30 min.

1.3 Structuring of the PDMS Membrane

[0126] In the case of photolithographic structuring, a negative lift-off photoresist 6 (marketed under the registered trademark AZ nLOF 2070, Merck KGaA) was applied directly onto the PDMS surface by spin coating at 3000 rpm (acceleration 1000 rpm/s) for 60 sec. Soft baking at 100 C. for 2 min on a hotplate resulted in a photoresist thickness of about 6.5 m. The exposure to light 7 with a chromium mask 8 employed a Suss MA6 mask aligner (350 W high-pressure mercury lamp) at a dose of 70 mJ/cm.sup.2. The subsequent baking (post-exposure bake PEB) was carried out on a hotplate for 3 min at 115 C. To prevent cracks from forming in the stabilized photoresist layer as a result of the different thermal expansion coefficients of the layers making up the multilayer structure, the light-exposed wafers were immediately transferred to an oven preheated to 100 C. They were then allowed to cool slowly to room temperature over a period of about 5 h. For development, the AZ developer (Merck KGaA, undiluted, high-speed configuration) was prepared in a laboratory jar on an analog orbital shaker (RS-OS 5 Phoenix Instruments). The structures were developed for 1 min 50 sec with slight movement of the fluid and then rinsed with deionized water and dried under a stream of nitrogen.

In the case of structuring of the metal layer in an aperture mask process, a 50 m nickel stencil mask 9 produced by applied microSWISS GmbH in a suitable UV-LIGA process was used. Since the mask had the outer dimensions of a standard 4-inch wafer, the mechanics of the Suss MA6 mask aligner were used to apply the mask onto the PDMS membrane surface by means of flat alignment and magnets. The surface-to-surface contact between the PDMS and the smooth mask surface ensured stable positioning through van der Waals interactions without the need for further fixation.

1.4 PVD Metal Deposition and Detachment

[0127] The vapor deposition 10 was carried out by thermal evaporation in an Edwards Auto 306 vacuum coating unit. To improve the adhesion of the 40 nm Au cover layer, an intermediate Ti layer of 4 nm was first deposited without any break in the vacuum (about 2*10.sup.6 mbar). After the coating process, either the photoresist was dissolved in acetone with slight agitation of the fluid and the resulting multilayer system then rinsed with deionized water, or the aperture mask was gently pulled off the PDMS surface. The UV-activated stabilizing transfer film 2 could then be easily detached from the wafer 1 without exposing the thin functionalized PDMS membrane 6 to significant stress.

2. Transfer Process

[0128] FIG. 3 shows the process of transfer to a cylindrical PDMS base substrate 11. The cylindrical base 11 was cast in a special polymethyl methacrylate (PMMA) mold having a constant outer diameter of 10 mm. The wall thickness was for the most part 400 m and in specific regions only 200 m. Since the specified transfer employed a connection of PDMS to PDMS via partial curing, it was in practice expedient to apply the intervening PDMS connecting layer by spin coating before detaching the film. PDMS-PDMS connection via partial curing permitted high connection strengths while being easy to execute. Here, a thin PDMS layer about 60 m in thickness was applied onto the top side of the structured layer by spin coating at 900 rpm for 60 s (acceleration 200 rpm/s) and then cured at 50 C. for 45 min. This resulted in stabilization of the PDMS film while maintaining sticky properties comparable to an intermediate layer of adhesive. The relevant portion of the specimen was then precut with a scalpel, the stabilizing transfer film 2 was detached from the handling wafer with tweezers (see step 4 in FIG. 2), and the partially cured PDMS surface was attached to the appropriate position on the cylindrical base 11 (step 1 in FIG. 3). The specimen was then placed in a cylindrical PMMA mold 12 and left therein for 48 h at room temperature so that it cured completely. As a final step, the transfer film 2 was detached from the connected membrane layer 13 (FIG. 3, step 2), and a further casting process (FIG. 3, steps 3+4) and subsequent curing at room temperature for 48 h carried out so as to obtain a uniform cylindrical sensor.

3. Characterization and Results

[0129] To ensure that the transferred metal morphology is not altered by undefined stresses after the last step, it was necessary to remove the finished PDMS cylinder from the casting mold with due care. The inner part of the casting mold, which defined the variable wall thickness of the PDMS base cylinder, was therefore replaced by a water-soluble adhesive wax (2-M19 soluble stic wax, Paramelt B.V.) before the transfer process. For this, it was necessary for the subsequent curing steps of the connection process and the final casting steps to be carried out at low temperature in order to avoid melting the wax (drip melting point approx. 57 C.).

[0130] FIG. 4 shows the finished PDMS cylinder with the integrated sensor structures. As proof that the process permits the handling and transfer of fragile surface morphologies, various surfaces (with microcracks and corrugated intermittent structures) were introduced by selective plasma pretreatment and also by varying the deposition rate. To characterize the morphology in the initial state prior to connection, after detachment of the handling wafer, and in the final state on the cylindrical base, the same structure was investigated in an SEM (Philips XL30) at each step. To characterize the morphology after transfer to the cylindrical base, a special aluminum holder simulating the curvature of the PDMS base was used.

[0131] FIG. 5 shows a selected morphology region of the prepared specimen in each relevant step of the described operation. As can be seen, the fragile crack morphology was unchanged during handling of the membrane, the sole change being slight compression owing to the curvature of the cylindrical base (step c), while neither delamination nor crack expansion was observed. In addition, simple two-wire measurements of the resistance showed that the electrical integrity of the structure was maintained at about 4 k.

[0132] Since there are various options for the process for connecting membrane to substrate, a 90 peeling test (see DIN EN 28510-1:2014) was carried out to determine the peeling force necessary to detach the cover film from the PDMS membrane (step 2, FIG. 3). For this purpose, specimens having a 100 m PDMS membrane that had been produced according to the substrate preparation process described above (step 1, FIG. 2) were detached from the handling wafer and the PDMS surface connected to the polished side of precut wafer pieces (30 mm wide) after activation in an oxygen plasma (30 sec at 100 W). The transfer film was then attached to the load cell of the peeling test device and the tests were carried out at a constant speed of 50 mm/min and a peeling angle of 90. Since the tests were limited by the size of the wafers and the width of the flats (wafers were cut perpendicular to the main flat close to the edges of the flat), the maximum peeling length was 90 mm and the peeling width used was 20 mm. A total of 5 samples between 20 mm and 80 mm peeling length were tested and analyzed to rule out edge effects. The average peeling force was determined to be 0.07 N/mm (SD 0.011 N/mm).

TABLE-US-00001 No. Peeling force [N/mm] 1. 0.076 2. 0.076 3. 0.082 4. 0.078 5. 0.051 0.07 Standard deviation 0.01