Micron-Scale Manufacturing

3D ablation (micromachining) of Nitinol. Note the part inside FDR's ear. (Image courtesy of Resonetics.)

What’s smallest part you’ve ever made?

If you’re in the automotive industry, it might be a valve body ball for an automatic transmission, at roughly an eighth of an inch. Components in the electronics industry can be smaller, but when it comes to micro manufacturing, there’s no bigger industry than medical devices.

It makes sense: if you’re manufacturing components for something that’s designed to operate inside the human body—where space is at a premium—the smaller, the better.

I recently had the opportunity to visit the corporate headquarters for Resonetics, a laser micro manufacturer for life sciences, located in New Hampshire, not far from Boston. In many ways, it resembled other manufacturing facilities I’ve seen, but with one important exception: to see the features on most Resonetics products, you need tweezers and a magnifying glass.

(Image courtesy of Resonetics.)

So, what is laser micromachining?

Resonetics CTO, Kevin Hartke, offered his insights into this unique technology.

Your company uses two processes for laser micromachining: direct-write and mask projection. Can you explain the difference between them?

Direct-write uses a single point, focused laser beam to process materials. This approach is analogous to CNC machining, but the laser is the tool bit. The focused laser beam can be as small as 5 microns, never goes dull and can process a wide range of materials (human tissue to diamond). For medical device applications, typical materials include metals and polymers.

(Image courtesy of Resonetics.)

Mask projection uses a high energy, poorer quality laser beam. The beam is homogenized, projected through a mask and focused onto the work surface. This approach has the advantage of processing many features at one time. For example, we can drill 8,000 6-micron holes in polymer film with a few pulses of the laser. This approach typically employs an excimer laser which emits an ultraviolet wavelength at high pulse energies which are well-suited for polymer applications.

Aside from the obvious difference in size, how does laser micro machining compare to the larger scale laser cutting of sheet metal and other materials?

Laser micromachining, or laser ablation, uses high frequency, short pulse duration lasers which have lower average power and very high peak power. Lasers used for ablation typically have 5-20 watts of average power and megawatts of peak power. This enables the selective removal of material without thermal damage and the ability to create very fine features down to single microns in size.

Hole arrays created via laser hole drilling in a variety of materials. (Image courtesy of Resonetics.)

Laser cutting of metal typically employs continuous wave or modulated lasers that have kilowatts of average power. These high-power lasers are employed to produce relatively large parts quickly by melting metal and removing it with a high-pressure gas.

When we looked inside the machines, I noticed a lot of mirrors. Why is the light path so complex?

We add a lot of proprietary additions to our systems including custom laser beam manipulation, process feedback and in-process monitoring.

You have a facility in Costa Rica, which probably isn’t the first place people think of when it comes to high-tech manufacturing. Why operate there?

(Image courtesy of Resonetics.)

We have located in Costa Rica to support the substantial local medical devices presence. Costa Rica has a strong technical workforce including technicians and engineers. Costa Rica has invested heavily in its education infrastructure and this is evident when hiring technical talent there.

Resonetics is currently exploring additive manufacturing. Does working at such a small scale present unique challenges for 3D printing? How are you looking to apply it?

Laser wire stripping of 0.003-in diameter nickel wire and laser welding of platinum/iridium and stainless steel electrodes. (Image courtesy of Resonetics.)

We are developing a proprietary process that drives additive manufacturing to the micro-scale. We have recently filed a patent on this technology and are in the process of commercializing it. We see a significant unmet need in the minimally invasive medical device space for this capability.

Your company currently sells complete systems as well as offering contract manufacturing services using those systems. How much business does each account for and do you expect this ratio to remain the same?

We are currently 90 percent contract manufacturing and 10 percent contract systems and expect our contract manufacturing will continue to grow much faster than our systems business.

How do you qualify parts made with laser micromachining?

Nitinol stent cutting with 25-micron struts with single micron standard deviation on geometry. (Image courtesy of Resonetics.)

We typically use a direct measurement method to check part geometry. We also have a very robust process validation standard for qualifying production parts.

Can you comment on the Lightspeed ADL and how it fits into your business more broadly?

All projects start in our Lightspeed Application Development Lab (ADL). We use these dedicated prototyping resources (engineers/technicians/equipment) to quickly develop customer prototypes. Once the prototypes have been developed we transition the project to our manufacturing group.

This seems like an industry that would benefit from the accuracy and precision of robotic automation. Can you comment on that?

We are starting to investigate the implementation of robotics. The primary challenge is that the size/shape of the parts we process are not straightforward to manipulate. We do use precision motion control for all part manipulation and most of our processes are semi-automated with the operators primarily loading/unloading machines and performing inspection.

For more information, visit the Resonetics website.