In surgical procedures, the last knot of a suture is crucial because it must hold the wound firmly in place to allow proper healing. But many surgeons struggle to apply the perfect tension. Tie it too tightly, and it can cut off the blood supply to the tissue, causing damage. However, if it is not tight enough, the wound might leak, or the repair could fail. Robotic surgeons also face difficulties because their electronic sensors lack the necessary tactile feedback or are too large for delicate procedures.
But this may not be a problem for much longer, as a surgeon and mechanical engineer have joined forces to create a mechanical transmission mechanism based on the slipknot that can help surgeons pull the final knot to the right tension every time.
Introducing Sliputure
Unlike many other knots that are permanent and hold tension rigidly, a slipknot is designed to slide and adjust under force. Building on this principle, surgery professor Cai Xiujun and aerospace engineering professor Li Tiefeng at Zhejiang University School of Medicine created a smart suture system called Sliputure in which the knot is engineered to open at a specific, preset force.
Sliputure is a special kind of suture made from standard surgical thread, which is used for the main suture. It features a tiny, pre-tied slipknot elsewhere along the thread that acts like a mechanical tripwire or tension fuse. When a surgeon or robot pulls the main suture to tighten the final knot, tension builds, and when a preset optimal tension is reached, the tiny slipknot releases.
Surgical skills boost
In tests published in the journal Nature, this slipknot mechanism delivered exactly the right kind of force 95.4% of the time. More importantly, the innovation helped inexperienced surgeons improve their knotting precision by 121%, allowing them to match the performances of veterans. And studies in animal models showed that closing wounds with Sliputure improved blood supply and tissue healing after surgery.
“Our slipknot-based system provides a simple, reliable, and cost-effective way to control force in both human and robotic operations, potentially transforming surgical practice and robotic safety,” wrote Xiujun Cai, senior author.
Ultimately, if this innovation is adopted, it will not only eliminate the guesswork of tying the perfect surgical knot but also provide a low-cost alternative to sophisticated electronic devices in surgery. That means it can be used in any medical setting, from high-tech robotic theaters to remote hospitals with limited resources.
Written for you by our author Paul Arnold, edited by Gaby Clark, —this article is the result of careful human work. We rely on readers like you to keep independent science journalism alive.
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More information
Yaoting Xue et al, Slipknot-gauged mechanical transmission and robotic operation, Nature (2025). DOI: 10.1038/s41586-025-09673-w
Journal information:
Nature
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