Kinematic Performance Assessment of Machine-Knitted Pneumatic Actuators for Hand Assistance

The rise of soft robotics allowed the development of inherently safe wearable exosuits capable of transmitting forces to the human body while being lightweight and streamlined. Over the last decade, we witnessed the rapid rise of textiles due to their great mechanical properties, which stem from their hierarchical structure, and compatibility with the human body. In this study, we investigated the design of a textile-based pneumatic actuator exploiting localized anisotropies to obtain bending motion kinematically compatible with a human finger. Four possible solutions were designed and manufactured using a computerized knitting machine, each featuring different knit architectures and geometries in their extensible regions (corresponding to the finger joints). An experimental kinematic validation was conducted to assess the designs and to compare their performance with the state of the art. The results show that the technique of short rows has an important impact on the kinematics of a knitted actuator, effectively recreating miniaturized pleats. Our preliminary results proved comparable to previous foundational literature studies, providing a promising starting point for new endeavors, with the ultimate goal of integrating them into a fully machine-knitted assistive hand exosuit.