Racing to Disrupt Industries Using Novel Manufacturing Methods

7/3/24 Pratt School of Engineering

A partnership between two startups with strong connections to Duke Engineering is looking to revolutionize a staple product of orthopedic surgery

a machine holding dozens of dripping staples
Racing to Disrupt Industries Using Novel Manufacturing Methods

Daniel Herrington didn’t know it at the time, but his dream of becoming a professional racecar driver provided the perfect training ground for becoming an entrepreneur.

During his four years at North Carolina State University, Herrington felt, as Tom Cruise so eloquently put it in the movie Top Gun, “The need. The need for speed.” Besides participating in the Wolfpack Motorsports Formula SAE student club, he was a driver for a handful of racing outfits: AIM Autosport, Andersen Racing, Bryan Herta Autosport and Leighton Reese Performance Group, to name a few.

And he was good at it, too. While he never quite made it to the level that competes in races such as the Indy 500, he won a few races in the Firestone Indy Lights Series—sort of like the AAA league of Indy Car—and finished seventh in points in 2009, the same year he graduated. But a couple of years later, he decided to change roadways and shift into the technology entrepreneur lane. And as it turned out, there were a lot of surprising similarities.

Daniel Herrington after winning the Chicagoland 100 at Chicagoland Speedway in 2009.

“There were definitely some translatable skills, like how to deal with risk and work under pressure,” Herrington said. “And if you need to raise money, you have to sell yourself and project a value proposition to potential sponsors. A lot of growing up happens in that process.”  

But before laying on the gas, he knew he needed to add more technical training to his trial-by-fire experience. After considering several options, he chose to take a pit stop at Duke’s Master of Engineering Management program.

That decision would greatly shape the course of Herrington’s eventual entrepreneurial career. After spending just over a year helping to launch technology startups for the U.S. government’s Advanced Research Projects Agency—Energy (ARPA-E), he decided he was ready to build his own startup. With his background in mechanical engineering, he decided to look into emerging manufacturing technologies such as 3D printing. But because so much investment had already been made in that space, he turned to a technology he’d learned about through a friend called electrochemical machining. And it didn’t hurt that one of his former Duke professors and mentors, Jeff Glass, director of the Institute for Enterprise Engineering, was an expert in electrochemistry and materials science.

daniel herrington

“I don’t have a PhD in materials science or anything, but Duke helped me a ton to know how to understand a technology, its value proposition and how it might move to market.”

Daniel Herrington CEO at Voxel Innovations

“I don’t have a PhD in materials science or anything, but Duke helped me a ton to know how to understand a technology, its value proposition and how it might move to market,” Herrington said. “It was a fantastic experience that helped me understand how to put what I’d practiced into real applications. And Jeff has been a great resource from both a technical and entrepreneurial standpoint through this whole process.”

That whole process has been nearly nine years in the making. Starting with a machine in his garage in Raleigh, Herrington secured a series of federal technology grants and eventually built his company—called Voxel Innovations—into a niche manufacturing company producing high-precision parts for companies in aerospace, energy and medical industries.

And, just recently, in a stroke of serendipity, they began supplying orthopedic staples for another Duke Engineering startup company called restor3d (said like restore-3D).

Customizing Orthopedic Implants

Around the same time that Herrington was attending Duke, Ken Gall, professor of mechanical engineering and materials science, was launching his own company based on novel manufacturing techniques. But since Gall was a few years ahead of Herrington’s own ambitions, he was able to get into the 3D printing market race.

Using direct metal laser sintering (DMLS) printers to solidify titanium and cobalt chrome alloy powders into thousands of thin layers, restor3d builds complex structures for orthopedic implants from the bottom up. Computed tomography (CT) images allow the company to create a computer model of a patient’s anatomy to print bespoke implants crafted specifically to the patient’s needs in only a few weeks.

“A lot of our implants are made in situations where there is no off-the-shelf solution that will work for the patient,” said Nathan Evans, senior vice president of product development at restor3d, who has been with the company for six years. “We work with surgeons to create truly unique one-off implants when there aren’t any other good options. And we’ve had some pretty incredible success stories doing that.”

The company has also expanded into the more traditional large-joint market, which serves a much larger market share in orthopedics. After all, think about it—chances are pretty good that you know of someone who has had major hip, knee, shoulder or ankle surgery. And rather than having a surgeon choose one of a dozen mass produced sizes, why not make the implant truly fit the patient?

In this same vein, the engineers at restor3d are always looking for a way to make their products better. Just like any other orthopedic implants, their devices require connective hardware like bone plates and screws. After connecting with one another through the Duke ecosystem, Herrington and Evans decided to work together to develop a more innovative version of one of the most common fixation pieces used in these types of surgeries.

Bone staples.

Elevating the Simple Staple

Staples in everyday life are pretty simple tools; they’re essentially just long pieces of thin metal that get bent back on themselves to secure paper or cardboard together.

Bone staples are more complex. Rather than being manufactured in an open U shape, they start off in a closed position. That way, when they’re forced open and inserted across two pieces of bone or a bone fracture, they squeeze together and put compressive forces onto the injured site. This not only makes the site more secure, it promotes healing across the injury.

While bone staples used to be made out of stainless steel, many companies are now making them out of a nickel-titanium alloy called nitinol. Besides being strong yet malleable and biologically inert, nitinol can be made to have a sort of shape memory to it, allowing the staples to provide even more compression within the bone.

A 3D rendering of the new bone staple being produced by Voxel for restor3d. Notice the small lip toward the top of the design that allows an inserter to grab on to it without having to cup underneath.

Based on the way that these traditional staples are designed and delivered, however, they sit above the bone a fair amount. Surgeons try their best to tamp them down into place, but most of the time, there will still be a few millimeters between the top ridge of the stable and the bone beneath it. And that can cause soft tissue irritation and impingement with surrounding bone, one of the most reported complications of bone staples.

“We don’t want to just rethink how large orthopedic implants are made,” said Evans. “There are lots of products along with the implants themselves that could be improved using new manufacturing techniques. And Voxel provided a great opportunity to do just that.”

A bone staple inserter grabbing hold of the new staple design.

Once engineers from restor3d identified an innovative staple design, they worked with Voxel Innovations engineers to bring the design to life with their novel electrochemical machining approach. This improved design features a cutout on the top cross section of the staple that essentially forms a lip for the staple inserter to grab on to enabling it to not come between the staple and the bone to deliver the staple with a much lower profile.

And Voxel’s electrochemical machining approach provides the perfect platform for producing the new staples. The technology works by essentially dissolving away unwanted material atom-by-atom.

nate evans

We don’t want to just rethink how large orthopedic implants are made. There are lots of products along with the implants themselves that could be improved using new manufacturing techniques. And Voxel provided a great opportunity to do just that.

Nate Evans Senior Vice President of Product Development at restor3d

Putting It All Together

Once a design for a product is created, an inverse image of it is created, sort of like a 3D stamp. This tool is moved to within micrometers of a solid piece of metal that will eventually form the final product. Once in place, an electrolyte solution—essentially water with some dissolved salts—is flushed through the space while electricity passes from the stamp to the metal being processed. The combination of the electrolyte and electricity strips away metal from the final product as the stamp slowly lowers and causes more and more metal to be dissolved.

The process does not create a buildup of heat in the final product, which could weaken its internal structure, and it leaves behind a perfectly smooth finish. For complex geometries, the product can be reoriented within the machine and go through the process multiple times.

There are only a handful of manufacturing companies using this approach, not just within the United States, but worldwide. It enables the machining of complex geometries while providing better tolerances and often faster machining times. It can also handle materials that are difficult to machine with other techniques.

Due to the rarity of the technology, getting it to work hasn’t come easy. Voxel has done everything from designing and building their own machines, writing their own software and engineering their own electrolyte. Everything has been completely soup to nuts.

“There’s a lot of parallels between restor3d and Voxel,” Evans said. “We didn’t invent these technologies, but we’ve both developed our own intellectual property and technology on how to apply it to get the custom solutions needed for specific applications.”

a machine holding dozens of dripping staples
An electrochemical machining device holding dozens of finished bone staples.

“At its core, this is about re-thinking what implant designs are possible with new manufacturing technologies,” said Herrington. “We at Voxel knew that the legacy designs of these implants were just driven by manufacturing constraints, and that our technology could potentially unlock a more optimal design.”

Besides having a lower profile when implanted, the staple’s new design can also be stronger, allowing a smaller implant or more force compared to other designs on the market, and is simple to use.  

“We’re rethinking what’s possible with the staple, using our novel manufacturing method to design features either not possible with other methods or really costly because it would require multiple machining operations,” Herrington added. “The product is set to launch next month, and from a surgeon’s perspective, its features give a clinical advantage over the mass-produced staples out on the market today.”

Speaking of mass production, Herrington says Voxel Innovations is planning to initially produce a few thousand of these new staples for restor3d to use per year. But that could just be the beginning.

“We work with Voxel because it’s a good fit for us. We are pushing the boundaries on novel manufacturing methods to make unique products, which is our ethos as a company,” said Evans. “Having said that, we look forward to introducing what we think is the best staple on market next month and deepening our relationship with Voxel as primary manufacturers for this product line.”

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