Laser technology has been supporting medical device manufacturers for decades. There is an excellent alignment between the processing capabilities of the laser and the manufacturing demands of medical devices, namely precision and quality. 

Many lasers are now available in the toolbox, supporting established processes (e.g., welding and cutting) to emerging techniques (e.g., micromachining and texturing). In many cases, the capabilities of lasers can be leveraged to solve unique manufacturing challenges and drive product innovation. This article takes a quick tour of how lasers are being used and will serve as a foundation for a series that will follow, each providing additional details on certain application areas.

Laser 101

The laser provides non-contact, optical energy focused onto the workpiece. A wide variety of lasers are now available that align with individual process requirements—whether creating a melt pool, minimizing heat effect, or optimizing material removal. Many lasers are operated in pulsed mode for precise control of power/energy/heat input. The length of the pulse relates to the process, with the Table listing the commonly associated applications.

The range of lasers is quite staggering if we consider the laser used for welding has a pulse duration of 10 orders of magnitude longer than one used for micromachining. It’s worth noting lasers, as production tools, have come a long way and now routinely support 24/7 high-volume applications for consumer electronics and automotive markets. As laser technology has ramped up in global manufacturing, increasing unit volumes have significantly reduced pricing, making the technology even more attractive from an ROI perspective. 

Additive Manufacturing

The medical device sector continues to be a pioneering industry for additive manufacturing (AM), not only for orthopedic implants but also for an array of high-resolution, fine tools and parts in metals, polymers, and ceramics. One of the key advantages of AM is that complexity is included for free. For example, the lattice structures that promote bone in-growth for implants, while almost impossible using another process, are well aligned to AM. Generally, low volume, high mix, or custom is where AM shines. However, unlike other widespread processes, AM remains somewhat limited to specialized contract manufacturers and OEMs. The reason is creating a part requires lengthy qualifications, in-depth knowledge of the complex build process, and a complete ecosystem of upstream and downstream processes needed to create the final part. 

Laser Welding of Metals

Welding was one of the first laser applications in this sector, and today, there are thousands of joining applications completed using lasers, from surgical instruments to catheters to guidewires. The growth is driven by four main factors: non-contact single-sided access, precise control of melt zone dimensions, extremely small heat-affected zones, and the ability to scale to the ever-decreasing size of devices. In the last 10 years, a transition has occurred from Nd:YAG to fiber technology for new devices based on cost—both purchase and running—as well as processing capability. Fiber technology offers excellent welding capability, especially for smaller parts, offering focus spot sizes down to 25 microns (0.001 in.) with excellent pulse stability for highly reliable welding.

A further feature of the laser is its flexibility and alignment with automated production. For example, if a part changeover requires a different focus spot size, this can be entirely captured in the part program using motorized optics (and not just defocusing). The motion requirements can be easily optimized rather than defaulting to linear stages. For example, a scan head (like those used on laser markers) can be used to direct the laser between spot welds in the blink of an eye or simplify and reduce the cost of motion for a seam weld. Lastly, one view into the future is post-weld inspection using AI/ML-based vision that has the potential to significantly reduce the labor burden of 100% inspection. 

Laser Welding of Plastics

While not as widely adopted as metal welding, plastic welding continues to grow its application base. Building on the foundation of precise welding, both for weld widths and heat input, the ability to implement in-process monitoring and control, and the capability to weld both clear and pigmented plastics are significant. Even more so than metals, polymers benefit from designing for laser welding, particularly for part tolerancing. Further, while migration from other processes is possible, care is needed. 

The lasers used for polymer welding are CO₂, fiber, and diode. As the CO₂ laser has high absorption in plastics, it is used for very thin materials, and the classic application is welding balloon catheters. One of the keys to welding success is matching the wavelength of the laser to the absorption characteristics of the polymer. In this regard, the diode laser is extremely useful as it can be wavelength-tuned over a relatively broad spectrum. 

Laser Cutting

Typically, when we think of laser cutting in medical device manufacturing, we think of stents. While millions of stents are cut every year, it’s worth remembering the process involves cutting thin, small-diameter metal tubes with human hair-sized features to microns of accuracy. Over the last 25 years, the process and the systems that produce stents have been iterated and honed to enable such volume precision. Beyond stents, there are a variety of parts—notably bone saws, heart valves, and hypo tubing used for interventional solutions. 

The laser is an excellent tool for cutting; again, it is non-contact, great for delicate parts, can be focused below 25 microns (enabling small feature sizes), and uses microjoules of energy into the part for precise heat input. Laser technology, like welding, has progressed from Nd:YAG to fiber, and recently, certain applications use femtosecond (fs) lasers. Fs lasers offer incredible cut quality for metals with burr-free cuts; however, in the past, their expense and slow cutting speeds limited usage to specialized applications. In the last few years, this has changed, as fs lasers are being increasingly used for nitinol and fine-featured cuts offering excellent ROI. One of the major downstream benefits is eliminating the de-burring operation and dealing with all the associated chemicals. In addition, as the cutting method is by sublimation (solid to vapor), the dimensional accuracy and repeatability are measured in microns, and the heat effect is almost non-existent. The fs laser, with very short pulses and extreme peak powers, can cut every type of material—whether plastics, ceramics, or glass—with excellent edge quality. 

Laser Marking

As marking is not a manufacturing process, it tends to get a bit of a bad rap—treated like the ginger-haired stepchild. However, tracking and traceability are vital, so marking has become a widely used process. Lasers directly mark the part; provide high flexibility in marking text, graphics, barcodes, and incrementing data; and use no consumables.

Medical device marking on metals is synonymous with “dark marking” on stainless steel and the cool blue color on titanium. The mark provides excellent visibility while avoiding trapping any dirt or debris, as the mark is flush against the surface of the part. One challenge for laser marking has been the ability of a mark to survive passivation or autoclaving without fading. With traditional laser markers, the mark may last a few hours, but the process would drift over time, causing the mark to fade and requiring significant rework. Mark reliability has been solved using short-pulse picosecond lasers. These lasers create a mark that is unaffected by even the most aggressive passivation or many cycles of autoclaving. 

Lasers also provide contrasting marks on many plastics—for example, providing high-quality marks on the outside packaging of devices. 

Laser Micromachining

Micromachining covers a variety of processes, including drilling, skiving (blind feature creation), and selective removal of layers or coatings (known as ablation). Removing material favors high peak powers and, therefore, pulsed lasers. Several lasers and pulse durations can be used; however, picosecond and femtosecond lasers offer material flexibility and extremely precise material removal. This can be measured in microns with process capability for plastics and mixed materials of metal and plastic. The advantages of using a femtosecond laser are similar for cutting—excellent edge quality and precise feature tolerance with almost no heat signature. 

In contrast with the other laser processes, the applications for laser micromachining are somewhat fragmented. More common applications include catheter processing, creating features for diagnostics, and selective removal of material for electrical connections.

Laser Texturing and Surface Functionalization

For medical devices, the key application is texturing implants to enhance osseointegration and vascularization characteristics and improve antimicrobial function. 

Summary

Laser technology and the medical device sector have been a great partnership. Looking ahead, this partnership will continue to grow as both established and new processes are developed, aligning with the ever-increasing manufacturing challenges for both materials and scale.

FURTHER READING: 4 Reasons Why Laser Optimization Is Essential for Medical Device Manufacturing

Geoff Shannon, Ph.D., has over 20 years of laser applications and systems experience in medical device manufacturing. He is currently principal of Laser Markets, offering marketing consulting services for lasers and laser systems. Dr. Shannon can be reached at geoff@lasermarkets.com.