Soft Transfemoral Prosthetic Socket With Sensing and Augmenting Feedback: A Case Study

In lower limb prostheses, the physical interface constituted by the socket is a crucial component for the device success. This work proposes a new design based on a rigid frame integrated into a silicone structure which allows for a more comfortable biomechanical coupling with the residual limb and facilitates the integration of smart technologies. This paves the way for new possibilities for prosthetic bidirectional interfaces or user health monitoring. Thus, four surface EMG sensors, three vibrotactile units, and nine temperature and humidity sensors have been integrated into the socket. These components enable the user’s motor intention decoding, provide augmenting feedback, and measure the residual limb thermal condition when wearing the prosthesis. The new socket was tested on a partecipant with a transfemoral amputation. The sEMG signals were registered during five different tasks in a circuit training and the classification median accuracy of an intention decoding algorithm was found to always be higher than 73%. The user’s perception of vibrotactile feedback was assessed through a psychophysical experiment and revealed vibrations from singularly activated units were the best perceived. Questionnaire results confirmed a high satisfaction level. However, tests on temperature and humidity suggest more efforts are still required in terms of skin perspiration.