Design and Development of Multi-Stiffness Expandable Tensegrity Structure as a Wearable Arm Brace

Abstract Tensegrity-based wearables offer a compact, effective, and simple solution to the absence of multi-stiffness braces. The multi-stiffness expandable tensegrity structure (METS) introduces an arm-conforming sleeve that dynamically adjusts stiffness using a continuous cable system and tailored unit cell designs. Unlike powered or rigid exoskeletons, METS provides biomechanical support without external energy, enhancing joint stability, supporting rehabilitation, and mitigating muscle overuse injuries. This research demonstrates the feasibility of the METS concept through iterative design, experimental testing, and nodal displacement analysis. A custom benchtop tester and the bending arm axial and twisting apparatus were developed to measure force–displacement and angle–weight metrics. These testers showed a 184% increase in 2D axial stiffness and an 86% increase in radial stiffness across repeated trials. Three unit cell configurations—Herringbone, Walking Man, and Armadillo—were evaluated, with Herringbone delivering superior stiffness modulation. In its un-tensioned state, METS exhibited stiffness comparable to an off-the-shelf compression sleeve; when the continuous control cable was tensioned, stiffness increased substantially—a capability that passive sleeves cannot provide. These results establish METS as a mechanically viable, passive, and user-adjustable wearable platform with potential for application in orthotic systems, rehabilitation, and wearable robotics.