Uploaded December 2025 | Updated September 2026, 1 week ago
Abstract
Mechanical transmission is essential in force-related activities ranging from the daily tying of shoe laces to sophisticated surgical and robotic operations. Modern machines and robots typically use complex electronic devices designed to sense and limit force, some of which still face challenges when operating space is limited (for example, in minimally invasive surgeries)6 or when resources are scarce (for example, operations in remote areas without electricity). Here we describe an alternative slipknot-based mechanical transmission mechanism to control the intelligent operation of both human and robotic systems. Through topological design, slipknot tying and release can encode and deliver force with a consistency of 95.4% in repeating operations, which circumvents the need for additional sensors and controllers. When applied to surgical repair, this mechanism helped inexperienced surgeons to improve their knotting-force precision by 121%, enabling them to perform surgical knots as good as those of experienced surgeons. Moreover, blood supply and tissue healing after surgery were improved. The mechano-intelligence exhibited in slipknots may inspire investigations of knotted structures across multiple length scales. This slipknot-gauged mechanical transmission strategy can be widely deployed, opening up opportunities for resource-limited healthcare, science education and field exploration.
Xue, Y., Cao, J., Feng, T. et al. Slipknot-gauged mechanical transmission and robotic operation. Nature 647, 889–896 (2025). doi.org/10.1038/s41586-025-09673-w
Abstract
Mechanical transmission is essential in force-related activities ranging from the daily tying of shoe laces to sophisticated surgical and robotic operations. Modern machines and robots typically use complex electronic devices designed to sense and limit force, some of which still face challenges when operating space is limited (for example, in minimally invasive surgeries)6 or when resources are scarce (for example, operations in remote areas without electricity). Here we describe an alternative slipknot-based mechanical transmission mechanism to control the intelligent operation of both human and robotic systems. Through topological design, slipknot tying and release can encode and deliver force with a consistency of 95.4% in repeating operations, which circumvents the need for additional sensors and controllers. When applied to surgical repair, this mechanism helped inexperienced surgeons to improve their knotting-force precision by 121%, enabling them to perform surgical knots as good as those of experienced surgeons. Moreover, blood supply and tissue healing after surgery were improved. The mechano-intelligence exhibited in slipknots may inspire investigations of knotted structures across multiple length scales. This slipknot-gauged mechanical transmission strategy can be widely deployed, opening up opportunities for resource-limited healthcare, science education and field exploration.
Xue, Y., Cao, J., Feng, T. et al. Slipknot-gauged mechanical transmission and robotic operation. Nature 647, 889–896 (2025). doi.org/10.1038/s41586-025-09673-w


![Pedaling in MRI machine
Purpose
To evaluate the effects of exercise on left ventricular parameters using exercise cardiac MRI in healthy adults without known cardiovascular disease and establish reference ranges stratified by age and sex.
Materials and Methods
This prospective study included healthy adult participants with no known cardiovascular disease or genetic variants associated with cardiomyopathy, enrolled between January 2018 and April 2021, who underwent exercise cardiac MRI evaluation. Participants were imaged at rest and after exercise, and parameters were measured by two readers. Prediction intervals were calculated and compared across sex and age groups.
Results
The study included 161 participants (mean age, 49 years ± 14 [SD]; 85 female). Compared with the resting state, exercise caused an increase in heart rate (64 beats per minute ± 9 vs 133 beats per minute ± 19, P less than .001), left ventricular end-diastolic volume (140 mL ± 32 vs 148 mL ± 35, P less than .001), stroke volume (82 mL ± 18 vs 102 mL ± 25, P less than .001), ejection fraction (59% ± 6 vs 69% ± 7, P less than .001), and cardiac output (5.2 L/min ± 1.1 vs 13.5 L/min ± 3.9, P less than .001) and a decrease in left ventricular end-systolic volume (58 mL ± 18 vs 46 mL ± 15, P less than .001). There were statistically significant differences in exercise response between groups stratified by sex and age for most parameters.
Conclusion
In healthy adults, an increase in cardiac output after exercise was driven by an increase in heart rate with both increased ventricular filling and emptying. Normal ranges for exercise response, stratified by age and sex, were established as a reference for the use of exercise cardiac MRI in clinical practice.
Ronny Schweitzer et al. Radiology: Cardiothoracic Imaging. Published Online:Jun 5 2025. https://doi.org/10.1148/ryct.240175 Pedaling in MRI machine](https://i.ytimg.com/vi/x-WuaLQc2Nc/mqdefault.jpg)







