Browsing by Author "Granberry, Rachael"

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    Active-Contracting Fabrics for Wearable Compression Applications
    (2018-09) Granberry, Rachael
    Compression garments are worn articles of clothing commonly used in medicine, astronautics, sports, and ready-to-wear fashion to provide a wide range of on-body pressures for purposes such as pressure therapy, enhanced mobility/performance, anatomical anchoring, or simple aesthetics. Current compression garment technologies are limited to pneumatic garment and undersized garments, each with their own challenges. Inflatable garments are dynamic, meaning pressures can be varied in quantity, duration, and location; however, these garments inhibit mobility and have a large mass, two factors which limit their use to stationary situations. Undersized garments are designed with stretch fabrics and/or cinching mechanisms, such as straps or lacing, to increase fabric tension around the body. Undersized compression garments are preferred when pressure is desired during daily and/or mobile activities because they are low-profile, do not inhibit mobility, and do not require a power source; however, the trade-off is lack of dynamic functionality. Active-contracting fabrics are an emerging area of research that could advance the capabilities of compression garment design by contracting on command. Shape memory alloys (SMA), for example, are active materials with shape memory properties and can be engineered to remember prescribed forms through an annealing process. Traditional weft knit architectures can be engineered to produce contraction if individual yarns incorporate SMA wire, causing large, dynamic displacements and contractive forces across the fabric surface that can be turned on/off or achieve various compression levels. This research addresses the compression garment technology gap by evaluating active-contracting fabrics, specifically contractile SMA knitted actuator fabrics, for on-body compression applications. Because the effectiveness of compression garments is dependent on the relationship between the garment and the body (i.e. fit), 50% of this work seeks to define the dimensions, range, and variability of the human body, while the remaining 50% seeks to quantify the performance of active-contracting fabrics. Specifically, this work (1) defines lower body static anthropometric variability through the development of a sizing system, (2) defines lower body dynamic anthropometric variability between different working positions to determine average dimensional fluctuation, (3) develops self-fitting, self-stiffening garments using active-contracting fabrics to address individual and population fit challenges, and (4) characterizes the actuation force of active-contracting fabrics for on-body compression applications. The outcomes of this manuscript are the following. (1) Lower body dimensional variability is vast. To accommodate 95% of the consumer population with a fitted, non-compliant lower leg garment would require hundreds of size categories, an approach that is not appropriate for the ready-to-wear market in the absence of mass-customization. (2) Lower body dimensional variability due to posture is minimal at the ankle and calf (max, 8%); however, changing dimensions at the knee and thigh (max 13% and 17%, respectively) may require special design consideration. (3) Active-contracting fabrics can be used in the design of self-fitting, self-stiffening garments that can accomplish actuation contraction up to 40%, a range that is suitable to reduce hundreds of sizes to a handful of sizes for a fitted, non-compliant, lower leg garment. (4) When displacement is fixed, or blocked, active-contracting fabrics can reach fabric tensions between 43 and 359 N/m. When wrapped around the body, these tensions translate to pressures ranging from 15-65 mmHg, depending on body radii. Additionally, these results revealed that increased SMA wire diameter and increased strain produce higher actuation forces. The results of this research endeavor conclude that active-contracting fabrics could be used in two distinct ways to accomplish the design of active-contracting compression garments. Self-fitting, self-stiffening fabrics could be actuated first to pull the garment close to the body and apply necessary strain to high-force compression fabrics. Once strained to their optimal actuation length, the high-force compression fabrics could apply the desired pressures. The results is a controllable, low-profile compression garment design that will be developed in future work.
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    Advancing the Fit, Performance, and Wearing Stability of Wearable Technologies with Active Textiles
    (2021-07) Granberry, Rachael
    Advancements in sensors and actuators have propelled wearable technologies toward wide-spread market use, however the physical interface between these technologies and the human body has remained a functional challenge. Passive fabrics are unable to conform around body surface concavities, resulting in reduced garment-body contact. Tunable gar-ment tightness/stiffness is presently attainable only with large-volume pneumatic actuators or manual adjustability mechanisms that increase device complexity and introduce fit in-consistencies. Wearing variability, or the variation in system placement, orientation, and tightness in relation to a body both between use trials and between users, can result in large variation and deterioration in system performance. This work investigates pervasive wear-able device challenges and proposes novel methods of exploiting active (shape changing) materials within wearable systems to accomplish enhanced fit, performance, and wearing stability of wearable devices. Fit, or the garment-body dimensional relationship, is investigated through the design of circumferentially contractile and thermally-responsive self-fitting garments. These self-fitting garments are composed of active textiles that accomplish enhanced garment-body contact by topographically conforming around complex body surface in response to body heat. Fit is further enhanced through the introduction of active auxetic behaviors, which enable active textiles to dynamically contract in two directions of a 2D structure (up to 30%in one direction and 40% in the other) for dynamic garment length and width adjustment. Performance, or the physical garment-body interaction that produces tightness/compression or locally-applied force, is investigated through the design of active textile-based medical compression devices that accomplish generated blocked forces up to 308 N/m for on-body compressive pressure over 55 mmHg. Lastly, wearing stability (in terms of consistent garment tightness across a user group) is demonstrated through design strategies and pattern making procedures, introducing methods to preserve garment performance across a user population. By exploiting the capabilities of active materials within the mechanics of fil-aments, yarns, textiles, and systems, this work presents key advancements for wearable device fit, performance, and wearing stability.