A Soft Fabric-based Shrink-to-fit Pneumatic Sleeve for Comfortable Limb Assistance

Abstract

Upper limb impairments and weakness are com-mon post-stroke and with advanced aging. Rigid exoskeletons have been developed as a potential solution, but have had limited impact. In addition to user concerns about safety, their weight and appearance, the rigid attachment and typical anchoring methods can result in skin damage. In this paper, we present a soft, fabric-based pneumatic sleeve, which can shrink from a loose fit to a tight fit in order to anchor to the limbs temporarily, thereby enabling the application of mechanical assistance only when needed. The sleeve is comfortable, ergonomic and can be embedded unobtrusively with clothing. A mathematical model is built to simulate and design sleeves with different geometric parameters. The best sleeve was capable of generating a friction force of 98 N on the limb when inflated to 25 kPa. This sleeve was used to create a wearable assistive device, integrated with a cable-driven actuator. This device was able to lift a 1.44 kg forearm rig up to 95 degree at low pressure of 20 kPa. The device was tested with six healthy participants, in terms of fit, comfort and assistive functionality. The average acceptable sleeve pressure was found to be 33±4.7 kPa. All participants liked the appearance of the sleeve, with a high average perceived assistance score of 7.33±1.6 (out of 10). The shrink-to-fit sleeve is expected to significantly increase the development and adoption of soft robotic assistive devices and emerging powered clothing.