T h e F u t u r e o f L a s e r

M i c r o M a n u f a c t u r i n g i n

M e d i c a l D e v i c e M a r k e t s

SEPTEMBER 2019

RESONETICS

PREPARED AND PRESENTED BY

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I n t r o d u c t i o nLASER MICRO MANUFACTURINGTECHNOLOGIES AND ITS IMPACT ONMEDICAL DEVICE MANUFACTURING

Laser micro manufacturing is a compilation oftechnologies developed to address an ever-increasing demand for micro-scalemanufacturing in the Medical Device andAdvanced Diagnostics Markets. Thesetechnologies include laser ablation, laser cutting,laser drilling, and laser welding.  Each technology addresses a common medicaldevice manufacturers' need to fabricate micro-scale medical devices in metals or polymers. Theadvantage of using a laser over traditionalmechanical processes includes no part contact,ability for micron scale features and minimalheat-input. These combined advantages areenabling miniaturization to occur across multiplemedical device applications with a direct pathfrom prototyping to production.  This article provides details on laser micromanufacturing technologies and applying themto medical devices.

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l a s e r a b l a t i o nLaser ablation is a method ofselectively removing materialresulting in micron scale featureson micro or macro scale metal orpolymer components. The materialis selectively removed viavaporization resulting from theexposure to a focused laser beamas shown in figure 1. Resoneticsemploys a variety of laser toolsincluding CO2 diode-pumpedsolid-state, excimer and ultrafast(picosecond and femtosecond)lasers.    

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Laser ablation continues to gain popularity anddemand as R&D engineers understand its benefits inminiaturization of devices.  Example medical device applications:

- Fine wire coating removal- Single and multi-lumen catheter tip shaping and outside diameter removal- Balloon surface texturing- Micro implants- Micro instruments

Figure 1. Schematic of Laser Ablation Process

    Laser ablation has been a beneficial process for advanced micro manufacturingof medical device applications because it offers a wide range of materialcompatibility resulting in a diverse scale of products.

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u n i q u e a p p l i c a t i o n s

As laser ablation technology enables newadvancements in the medical device industry, newapplications are materializing that push theboundaries of micro manufacturing. One example is 3-D ablation, which was a processdeveloped to support unmet customer needs in theneurovascular market. CHALLENGEA customer required a metal part that was ten timessmaller than a Swiss CNC machining process couldprovide. SOLUTIONResonetics developed a micro-scale ablationtechnique that enabled this neurovascularapplication through a combination of advancedultrafast laser technology, motion control andcustom software. This technology proved versatileenough to serve additional applications in theophthalmic and cardiovascular markets.  See figures 2 and 3 (right) for application examplesof 3-D ablation.

Figure 2. Micro Jaw NitinolComponents Outside Diameter1.1049mm, 0.0889mm Wall Thickness

Figure 3. 3-D Laser Ablation of NitinolComponent. Dimensions: ID 0.137mm /OD 0.343mm

3-D LASER ABLATION

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LASER ABLATION CONTINUED.

The major benefit of ASSURE End Point Detection™ is that coated wires can bestripped uniformly and consistently, independent of the inevitable variation of thewire coating from lot to lot or even within the same spool.

SOLUTIONTo ensure 100% removal of each coatinglayer and to minimize undesiredincursion into the next layer, Resoneticsdeveloped and patented a uniqueclosed-loop process control calledASSURE End Point Detection™. Bymonitoring the plasma plume at theablation point, whose signaturediscriminates between materials ofsubsequent layers and detects presenceand type of remaining material, the lasercan turn on and off to avoid going toodeep in the thinner sections of the wirecoating or removing too little in thethicker sections (V, VI).

Figure 4. Laser Wire Stripping Using ASSURE End Point Detection™, Wire Diameter  0.100mm

CHALLENGEIn figure 4 below, we show cross-sections of an ideal multi-layer coatedwire (I) and a real wire with(exaggerated) non-concentricity issues(II). The coating layers are thicker insome locations and thinner in otherlocations around the wire. If we laserstrip the wire in an open-loop process(i.e. delivering the same number ofpulses at all rotational locations), thenthe end result is an uneven, non-uniformly stripped wire with remainingcoating layers as well as a possibility ofcore wire damage at some rotationallocations (III, IV).

Another unique application of laserablation is laser wire stripping. Thisprocess involves the removal of theouter coating to expose the underlayinglayer or the core metal wire.

W I R E S T R I P P I N G

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L a s e r c u t t i n g

Laser cutting uses a focused laser beam tomelt or ablate material which is removedvia a coaxial gas nozzle as shown in figure5 (right). This process is well-establishedand used extensively in the manufacturingof medical devices.  Laser cutting typically uses a Nd:YAG orfiber laser. In addition to Resonetics usingthese lasers, they have also developedultrafast (picosecond and femtosecond)laser cutting to eliminate heat input whichminimizes downstream part processing.  Ultrafast laser cutting can be used forvarious types of metals and polymers withbenefits including; no heat affected zone,clean cut edges and no burrs. See figures 6 and 7 (below) for applicationexamples of laser cutting.

Figure 6. Stainless Steel Laser Cut Hypotube (LCT).Larger Diameter LCT 4.572mm OD x .4.2164mm ID 

Figure 5. Laser Cutting Process Diagram

Thin walled stentsDelivery system componentsPull ringsBioresorbable scaffolds

Exa m p l e M e d i c a l D e v i c e Ap p l i c a t i o n s :

Figure 7. Small Diameter LCT 0.4445mm OCD X0.3429mm ID

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I n n o v a t i v e C u t t i n g P r o c e s s e s

APPLICATIONS AND ADVANCEMENTS FOR THE MEDICAL

DEVICE INDUSTRY

Resonetics has combined advances in laser andmotion control to develop a cost-effective tool forhigh-volume manufacturing catheter components.This high-speed laser cutting process is calledPRIME™ Laser Cut. The laser cut hypotubes (LCT) from the PRIME™process have many advantages over traditionalcatheter manufacturing methods (such as braidedcoil construction). Below are key benefits ofPRIME™ Laser Cut LCT catheter components:

Customization: a key benefit of LCT overtraditional catheter construction is the ability tocompletely customize the part geometry to matchthe clinical demands of the catheter. For example,if you are designing a catheter with significantstiffness on the proximal end but require uniaxialflexibility on the distal end this can be difficult toachieve with a traditional braiding/coilingtechnique.  Torque Transfer: LCT typically employsinterrupted cutting which enables flexibility butmaintains a monolithic connection from proximalto distal ends of the catheter. This directconnection ensures a good torque response whenfunctioning the device in-vivo.

Example of  Laser Cut Parts

PRIME™ Laser Cut Hypotube

Kink Resistance: an additional advantage of the monolithic aspect is optimizedkink resistance. As devices become more flexible they inherently have a higher riskof kinking upon insertion/propagation through the anatomy. The PRIME™ processenables the design of flexibility and optimization of kink resistance withoutsacrificing functionality.

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n i t i n o l c u t t i n g

INNOVATIVE CUTTING PROCESSES CONTINUED

Resonetics has also developed advances in nitinol cutting using ultrafast lasertechnology. Nitinol is used extensively for the fabrication of catheter componentsand implants and is sensitive to thermal heat input. Figure 9 below shows an ultrafastlaser cut nitinol part. Beyond the elimination of heat input, ultrafast laser cutting alsoprovides a part that is closer to near net shape which minimizes the downstreamrequirement for electropolishing.

Figure 8. Prime™ Laser Cut Examples with Varying Cut Pitches

Figure 9. Nitinol Stent with 0.025mm Strut Width Cut with Ultrafast Laser

Ovality: a challenge with braided/coiled catheters is flattening or ovality as theymove through difficult anatomy. Since LCT is monolithic it does not collapse as itpropagates tortuous anatomy. This is critical when passing additional devicesthrough the inner diameter of the catheter. Low Profile: LCT based catheters can start with a relatively thin-wall tube (downto <0.0005”) while maintaining the strength requirements of the catheter. Againthe monolithic benefits of LCT enable a reduced wall thickness of the catheterwhich opens up space for larger devices passing through the inner diameter.

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l a s e r d r i l l i n gPROCESS AND APPLICATIONS

Laser drilling is an ablation process that uses a focused laser beam to createmicron scale thru-holes. As shown in figure 10 below, the process uses a focusedlaser beam to drill holes and is considered advantageous for medical devicemanufacturing due to its precision and efficiency. Laser drilling enables thefabrication of holes down to single microns in diameter, which cannot be achievedby standard drilling methods. The process can also be performed on a widevariety of metals and polymers, eliminating heat damage and maintaining theintegrity of the product being manufactured. Some popular applications that uselaser drilling are embolic protection filters and infusion catheters.

Catheter balloons are a commoncomponent used in severalminimally invasive procedures. Some procedures requirefunctionality beyond simple inflationsuch as localized drug delivery.Laser drilling enables thefabrication of drug delivery balloonsby creating micro-scale holes acrossthe surface of a balloon. A perfectcase, where balloons arerepresented by ideal geometricforms (typically cylinders andcones), this can be achieved by asimple set up and alignmentprocedure and straightforwardmulti-axis positioning control.However, real-world balloons candeviate from ideal geometric form,which requires new process controlstrategies.

Embolic protection filtersInfusion cathetersFlow access holesMicro hole arrays

Exa m p l e : L a s e r D r i l l i n g Ap p l i c a t i o n s

Figure 10. Laser Drilling Process

Example of Laser Textured Balloon

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B a l l o o n a n d c a t h e t e r s

A good example of drilling is an array ofholes covering the conical end of aballoon (shown in figure 11, right). Forthis application, a scanning maskmethod is used as described in USPatent 7,812,280 “Method andapparatus for laser micromachining aconical surface”. However, when theconical end of the balloon is not a truecone, the geometric distortion affectsthe hole pattern as it is mapped ontothe cone. To deal with this problem,Resonetics’ has developed a processcontrol method for on-line, automatedmachine vision mapping of the balloongeometry, and a proprietary algorithmto provide real-time adjustments.

Another application example is laserdrilling multi-lumen drug deliverycatheters.  In such catheters, thedrug is distributed through smallsatellite lumens. The requirement isto drill small holes or arrays of holesthrough the outer wall of thesatellite lumens without perforatingthe inner wall. This is accomplishedby incorporating an in-situ opticalinspection to detect inner walldamage as an end-point detectioncontrol method to prevent excessiveablation of the lumen inner wall.

LASER DRILL ING CONTINUED

Figure 11. Laser Drilled Holes Coveringthe Conical End of Balloon

Figure 12. Holes Drilled in Polymer Catheter Extrusion

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l a s e r we l d i n g Laser welding is a process that joinstogether two parts of similar materialcomposition without the use of a fillermetal. As shown in figure 13, this processutilizes a focused beam to locally melt andfuse metal with minimal heat affectedzone. The low heat input aspect of theprocess maintains the integrity of the basematerial and prevents distortion of the finalassembly.

Figure 13. Schematic of Laser Welding Process

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APPLICATIONS AND TECHNOLOGIES

Laser welding is particularly useful for micro scale medical devices that are toosmall to be joined by traditional welding methods. The process is used acrossseveral medical device markets including neurovascular, structural heart,ophthalmic, electrophysiology, interventional cardiology and sports medicine.

Resonetics is called upon to provide solutions inlaser welding applications that have a high levelof difficulty or complexity. These applicationstypically require a focus on the following processcontrol concerns: Geometry control: Part geometry cannot varymore than 10% of the smallest part feature,dictating single micron tolerances on all parts. Part fixtures: Fixture design and fabricationrequires specialized laser micro manufacturingcapabilities.

Figure 14. Laser Welded Wire to Pull Ring

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Pull ring assemblies ( Figure 14)Thin wire components for deliverysystems (Figures 15 & 16)Micro implants

Figure 15. Laser Welded Wire to Cannula

Laser stability: Laser systems must be industrial,robust and stable, requiring the precisemeasurement, monitoring and control of the laserpower. Low cost jewelry welding lasers lack thepower stability to guarantee a stable process.  Part handling: Part manipulation requires skilledtechnicians who use micro-manipulators with theaid of optical microscopes.

From the beginning, laser welding processes are designed with manufacturabilityand repeatability in mind, accelerating the product time-to-market by allowingcontract manufacturers to deliver quick-turn prototypes, followed by scalablevolume manufacturing.

LASER WELDING CONTINUED .

Figure 16. Thin Wire Welding 0.075mmDiameter Nitinol Wire Assembly (Top), HighMagnification View of the Laser Weld(Bottom)

Moving seamlessly from development toproduction requires expert laserknowledge of the process parameters,material weldability, geometry control,fixture design/manufacturing and parthandling. Collectively these factors arecritical for a successful implementationof micron-level laser welding for themost difficult medical deviceapplications.

Exa m p l e L a s e r W e l d i n g Ap p l i c a t i o n s :

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c o n c l u s i o n

This technical paper has highlightedlaser processes including ablating,cutting, drilling and welding. Itdiscusses the latest technologybreakthroughs and how you can usethem today. At Resonetics, we specialize in applyingthe leading edge laser processingtechniques to your medical devices. Wehelp you develop and iterate quickly toget your device to market fast. Tochallenge our laser experts or to learnmore, contact us.

www.resonetics.com

sales@resonetics.com1.800.759.3330

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