Flexible tweezers awarded

Tim Nai now orients towards logistics - Photo: Tomas van Dijk

Tweezers that can work ‘round the bend’ could make knee operations faster and safer. Recent graduate Tim Nai’s design of these tweezers won him the Wim van der Hoek Constructor’s Award.

Tim Nai graduated from the faculty of Mechanical, Maritime and Materials Engineering in January of this year, after which he travelled to China to learn Mandarin Chinese (on top of the Cantonese that he had learnt at home). After China, Nai continued his travels through Asia. When he returned home to Holland, almost a year later, he was surprised when his thesis supervisor, Dr Just Herder, called, insisting that he should attend the annual conference of the Dutch Society for Precision Engineering, held earlier this month. At the conference, Nai was even more surprised when he was awarded the Wim van der Hoek Constructor’s Award for special achievement in the field of mechanical engineering.

Nai’s graduation project involved devising a flexible tool that allows surgeons performing knee operations to work ‘round the bend’ in the knee.
“Current surgical tools are not flexible,” explains Dr Gabriëlle Tuijthof, Nai’s co-supervisor. “Instead, a surgeon will use multiple punches from a set of 15 to 20, each with different angles to reach difficult corners in the knee joint.” Switching between tools costs time, bothers the patient and increases the risk of infection. The tweezers that Nai developed however have a flexible shaft, capable of bending 25 degrees to left and right.

Designing it was no easy feat. “It cost me a year and a half,” Nai says. “To convey large forces, the shaft had to be both stiff and flexible. That’s a difficult combination.”
Nai began his research by making an inventory of flexible mechanisms, eventually choosing a principle called ‘rolling link’. Nai: “A rolling link consists of two convex surfaces in contact with each other. It works like a knee joint and can convey large forces under different angles.”
Nai won the Wim van der Hoek award in part for the elegant way in which he produced the tool’s joint from a single 3-millimetre wide steel bar. A single, very thin (0.028 millimetre) steel string holds the convex steel surfaces together, with a laser used to cut the surfaces and metal string from one metal bar.

The tweezers are not ready for market yet, says Dr Jules Scheltes, from Deam, who specialises in marketing innovative medical tools: “You must have a working prototype – not only the shaft, but a fully functional beak and a handle, so that surgeons can try it out.” Moreover, medical markets are difficult to penetrate: a new tool only has a chance of gaining acceptance if it shortens the operation time, allows for new operations to be performed, or substantially reduces the risk of complications. Another TU Delft student will now develop a beak for Nai’s award-winning tweezers.

Demonstration video of prototype