This innovation represents a paradigm shift in lower-limb prostheses, offering a flexible, lightweight, and customizable solution for the development of soft robotics by integrating advanced materials, drives, and sensors. Image courtesy of Peking University.
A research team at Peking University, Beijing, China, has developed what they claim is the world’s first soft prosthetic knee.
Compared to the rigid, high-density metallic mechanics of prosthetic knees, soft materials enable lighter, more flexible designs with better compliance and impact absorption. However, challenges such as inefficient deformation under load have hindered their application. The new design overcomes these limitations with an innovative solution: The soft prosthetic knee features an origami structure, reinforced with polymer blocks and a connection system for the thigh and calf. Weighing only 300 g and standing at 15 cm, the design of the prosthesis allows for a broad range of motion, meeting the dynamic movement needs of the knee.
The team introduced a fold structure that mimics the human knee’s polycentric rotation. By adjusting design parameters, the prosthesis achieves highly accurate joint movement that replicates natural knee function. To enhance weight-bearing capacity, the back-fold structure creates a pneumatic chamber, simulating the hydraulic pressure of horsetail cells. Reinforced folds reduce unnecessary deformation, improving the accuracy of motion control. The prosthesis demonstrated precise movement under pneumatic control, with performance closely matching theoretical predictions. It also absorbed impact forces by 11.5% to 17.3%, held weight of over 75 kg (250 times its weight) and generated more than 25Nm of torque.
In treadmill walking tasks, participants were able to walk at both normal and fast speeds with improved gait symmetry, experiencing less fatigue and lower impact. Additionally, the prosthesis performed well in multi-terrain and outdoor scenarios, such as walking on stairs and ramps, and crossing obstacles.
