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From Legos to Medical Devices

Thu, 06/06/2013 - 11:38am
Lindsay Hock

An early interest in robotics led Nikolai Begg, the 2013 Lemelson-MIT Student Prize winner, to the medical device field, where he found a new solution for surgical puncture access.

Nikolai Begg received the 2013 Lemelson-MIT Student Prize for his portfolio of novel medical devices. Photo: Lemelson-MIT ProgramIn seventh grade, now 25-year-old Nikolai Begg, 2013 Lemelson-MIT Student Prize winner and graduate candidate in mechanical engineering at Massachusetts Institute of Technology (MIT), was assigned a general project for English class where he had to pick a topic, do research, interview someone, and then write a report. That year, in life science class he took a great interest in this field, choosing to write his report on surgical robots. Able to interview surgeons using surgical robots and engineers designing them, Begg discovered an incredible field that left him with a “galvanizing feeling” that he could do what he loved: tinkering and building with Legos in the field of medicine. And, hopefully, his efforts could one day help people or save a life.

Fast forward to Begg’s MIT undergraduate studies where he studied mechanical engineering, and realized his interest in surgical robots could become a possible career. Able to watch doctors at work and stand in operating rooms, Begg started to observe surgeries conducted at local hospitals. He quickly noticed that laparoscopic surgery is a great, gold-standard, revolutionary procedure. However, the first step in such a surgery—where the surgeon inserts a spear-like device into the patient’s abdomen—appeared strikingly imprecise and rather brutal. “It basically started with the surgeon almost stabbing the patient,” says Begg, “and that problem stuck with me into my master’s program when I realized I wasn’t the first to notice this at all.”

A well-recognized problem in the medical field, trocar access accounts for about half of the complications in laparoscopic surgeries, leading to internal trauma, infection, and pain, according to a 2003 report conducted by the U.S. Food and Drug Administration.

“If you’ve ever drilled into a wall, you can appreciate the problem at hand where the drill bit first punctures through the wall and you jerk forward because, for a fraction of a second, you’re still applying force to the device since your brain hasn’t reacted to the change of force,” says Begg. This could lead you to hit a gas pipe or electrical circuit behind that wall. It is this acceleration of a puncture device into a patient’s body which leads to the risk that a surgeon could puncture too far and plunge into an organ, blood vessel, or another part of the body.

“In my master’s work, I decided to tackle this problem, and realized it’s more difficult than just laparoscopic surgery,” says Begg.

“Try to think of a time you went to the doctor and they didn’t prick you or stick you with some needle,” continues Begg. Almost every medical and surgical procedure includes some element of puncture access. Whether it’s gaining access to your veins with a hypodermic needle; inserting an epidural through a person’s skin and muscle to the spine; or even drilling into the brain to relieve pressure during brain surgery, they all include this element of puncture access. This realization led to his puncture access mechanism, which is a large improvement over other puncture access technologies and techniques, and led to his $30,000 Lemelson-MIT Student Prize win, one of the most prestigious student prizes, for making surgical procedures less invasive and risky.

Before Begg, others tried to solve this problem, as it is ubiquitous throughout the medical field and over many applications. Surgeons tried sensing techniques like ultrasound to see exactly how deep an object must puncture before it passes through the tissue. But the technologies aren’t cost effective and still rely on guesswork during surgery. Puncture access devices with spring-loaded shields are another option, in which the shield springs forward to cover the blade of the device so it only punctures the right amount through tissue. But in use, the shields aren’t always fast enough to prevent over-puncture. In laparoscopic surgery, a blunt trocar device is used with no blade, making surgeons apply a much greater force to insert the instrument, resulting in a much greater acceleration at the moment of puncture. Begg’s force-sensing puncture access mechanism device is different from the previous solutions as it retracts the instrument’s tip at the moment of puncture, actively opposing its forward acceleration.

The mechanism works where the tip of the device is connected to a retraction spring by a flexural linkage. When the tip is advanced and pressed against tissue, the links expand and lock the mechanism in place with friction. The moment the tip punctures the tissue and the force of the tip becomes zero, a mechanism unlocks and the spring retracts the tip. Altogether it takes the tip less than 1/100th of a second to retract back into the device, eliminating over-puncture and other problems commonly associated with previous attempts at puncture access technologies. Purely mechanical, the mechanism has few parts and is scalable for many medical puncture access devices.

When developing the mechanism, Begg used many different technologies and processes, but his master’s degree work on developing the flexure technology within the device started with many prototyping cycles. “I always try to build things as much as possible because when you can hold the product in your hand, view it, use it, take it apart, and see how it works or breaks, you can understand better the final product,” Begg says. He used prototyping methods from traditional machine tools to laser cutting and water jet cutting to create different versions of the flexure mechanism to test its mechanics and see how it behaved. “I also used Solidworks to model the different prototypes to see how they move and how they behave,” Begg continues.

The technology is scalable down to a hypodermic needle for gaining access to a vein all the way up to a brain drill for drilling into the space between the skull and the brain, which is unique from other puncture access devices that serve one application. Depending on the application and the amount of force needed to create the proper puncture, construction materials of the mechanism vary. In applications where the forces involved are lower, plastics with good elastic properties create the flexure. For higher force applications, such as drilling into the brain, metal is used—mostly stainless steel, titanium, or other medical-grade material—for the flexure mechanism.

The flexural mechanism has a small footprint and does not add significant size to the device; the smaller the device, the greater an increase in size due to the mechanism. In many applications, the mechanism occupies space in the device casing that would normally be empty, just to fit comfortably in the user’s hand, or replaces a different mechanism or components used to activate a blade cover or guard. In these cases, the size of the device is the same as a current puncture device.

As with any technology, Begg faced challenges in the product development such as tolerance buildup. “There is always the challenge of manufacturing tolerances when engineering something and being precise enough in your method that you can develop design equations that reliably govern how your mechanism is going to behave,” says Begg. He also faced design challenges. In the initial concept, Begg believed he had to slightly undersize the flexure so it could easily fit into the device during assembly. But because the flexure was undersized, more force was required to lock the mechanism, often leading to device malfunction. Using a principle that he calls “reciprocity”—where if something doesn’t work, do the opposite—Begg oversized the flexure and compressed it to fit the device. In compressing the flexure it provided more locking force, causing the mechanism to behave more reliably.

Now Begg is looking at the best applications to gain FDA approval and reach clinical use of his mechanism, which is already protected by two patents.

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