INTRODUCTION: Aerospace orthostatic intolerance garments (OIG) have historically been pneumatic (e.g., NASA's antigravity suit), an approach that inhibits mobility and requires connection to an air supply. Elastic compression garments, an alternative technology, are difficult to don/doffand cannot be worn in a noncompressive state, resulting in discomfort and usability challenges. This research evaluates a novel technology-contractile shape memory alloy (SMA) knitted actuators-that can enable low-profile, dynamic compression for an aerospace OIG. METHODS: To characterize the functional capabilities of SMA knitted actuators, displacement control testing was conducted on 10 actuator samples with a range of geometric design parameters. Inactive (FI) and actuated forces (FA) were observed by repeatedly thermally cycling each sample at 0%, 15%, 30%, and 45% structural strain. Compression capabilities were approximated using medical compression hosiery standards and anthropometric data from a representative aerospace population (ANSUR 2012). RESULTS: Dynamic compression predictions reached 52 mmHg (single layer fabric) and 105 mmHg (double layer fabric) at the ankle. Low, inactive pressures (p, 20 mmHg) demonstrate that compression is controllable and can be dynamically increased upon actuation up to 33 mmHg in a single layer system and up to 67 mmHg in a double layer system. DISCUSSION: The results highlight the potential of SMA knitted actuators to enable low-profile, dynamic compression garments that can reach medically therapeutic pressures on an aerospace population to counteract OI symptoms. In addition to astronautic applications, this technology demonstrates widespread terrestrial medical and high-performance aircraft applicability.
Bibliographical noteFunding Information:
Financial Disclosure Statement: This work was supported by a NASA OTC Space Technology Research Fellowship (grant number 80NSSC17K0158) as well as by MnDRIVE RSAM. The authors have no competing interests to declare.
A special thank you goes to members of NASA's Johnson Space Center as well as University of Minnesota peers from the Wearable Technology Lab (WTL) and the Design of Active Materials and Structures Lab (DAMSL). Trade names and trademarks are used in this report for identification only. Their usage does not constitute an official endorsement, either expressed or implied, by the National Aeronautics and Space Administration. Financial Disclosure Statement: This work was supported by a NASA OTC Space Technology Research Fellowship (grant number 80NSSC17K0158) as well as by MnDRIVE RSAM. The authors have no competing interests to declare.
© 2020, Aerospace Medical Association.
- Functional fabrics
- Medical compression
- Orthostatic intolerance
- Shape memory alloys