Hydraulic Fabric Muscle Actuators for Wearable and Soft Robotics

Advances in soft robotics are yielding transformative technologies for augmenting human and robotic capabilities, enabling new functionalities and expanding the ranges of environments and tasks that humans and robots can operate in, and the activities they can perform.

Research in our lab has yielded soft, active textiles that are thin, low-volume, stretchable, conformable, human-safe, and capable of efficiently producing large in-plane strains, and high stresses or forces. They can be compared to sheets of human muscle. These devices can strain, squeeze, bend, and conform to hard or soft objects of arbitrary shapes or sizes, including the human body.

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The textiles are actuated via an efficient hydraulic transmission comprising fluid channels in arrays of hollow elastic fibers that are integrated within a composite fabric. We pattern the textiles to possess anisotropic stiffness using methods that can be integrated in standard apparel engineering processes. The imposed anisotropy directs the fluid input to exchange mechanical energy with the elastic fibers, generating large forces and displacements.

 

Our textile actuators can be designed to produce linear forces of hundreds of Newtons and displacements of greater than 100%, at bandwidths greater than 5 Hz, with efficiencies exceeding 80%, far outperforming alternatives such as shape-memory alloy textile composites.

The efficiency of hydraulic actuation is due to the incompressibility of water, which avoids energetic losses associated with compression. Incompressibility also increases safety, because little potential energy is stored in fluid compression. At typical working pressures, a rupture of our hydraulically actuated textiles yield harmless leaks. In wearable applications, we are integrating these devices with textile-integrated sensors for physiological sensing, interactive force assistance, and haptic feedback.

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Composite actuators can realize multi-axis stresses for applications in wearable and soft robotics.

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In wearable applications, the devices can apply beneficial compressive stresses, aiding circulation and muscular recovery after exertion.

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References:

M. Zhu, T. N. Do, E. W. Hawkes, Y. Visell, In Preparation, 2019.

Y. Visell, E. W. Hawkes, M. Zhu, T. N. Do, Soft Actuator and Method of Making the Same. United States provisional patent No. 62 731,583. Filed 1 October, 2018.