Advancements in e-textiles, 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. Prior research has found that system-body interface challenges produce wearing variability, or variation in system placement, orientation, and tightness in relation to a body both between use trials and between users, resulting in large variation and deterioration in system performance. We break down the mechanics of common system-body interface challenges through a summary of design principles critical to any system interfacing with the human body. Additionally, we present an active interface based on shape memory materials that dimensionally adapts to its user's dimensions. An experimental investigation of these active system interfaces considers the impact of design variables often overlooked in the design process. Recommendations are provided to optimize interfaces for the requirements for a given wearable technology. Additionally, we illuminate methods to reduce wearing variability for a range of users to produce consistent system-body interaction across a user population. Through these active interfaces, we advance a broad range of wearable technologies, including wearable sensing, motion tracking, haptics, and wearable robotic devices.
New medical compression technologies that are simultaneously low‐profile, facile to don, and dynamic—applying medical compression only when needed—can expand the use of wearable compression, increase patient compliance, and lead to better medical outcomes. Dynamic and conformal wearable compression devices are presented that can be donned in a low‐stiffness state and transition into a high‐stiffness and, consequently, high‐compression state, on‐demand. These devices are enabled by active textiles developed from custom NiTi filaments that remain inactive at room temperature and accomplish actuation proximal to the human body surface. Further, these compression devices exploit NiTi material hysteresis to sustain a high‐compression state post‐heating and upon equilibrium with the body surface temperature for thermally‐comfortable, on‐body performance. Two case study examples—1) a consumer medical compression device and 2) a custom astronaut compression device—demonstrate the generalizability and flexibility of the engineering and design methods to develop a range of dynamic, tunable, and conformal compression devices with different goals and requirements. Further, this work demonstrates a roadmap for developing wearable systems that can accommodate a range of users without sacrificing system performance. This research opens doors for new NiTi‐based medical and consumer applications that interface with the body surface.
Upper limb mobility impairments affect individuals at all life stages. Exoskeletons can assist in rehabilitation as well as performing Activities of Daily Living (ADL). Most commercial assistive devices still rely on rigid robotics with constrained biomechanical degrees of freedom that may even increase user exertion. Therefore, this paper discusses the iterative design and development of a novel hybrid pneumatic actuation and Shape Memory Alloy (SMA) based wearable soft exoskeleton to assist in shoulder abduction and horizontal flexion/extension movements, with integrated soft strain sensing to track shoulder joint motion. The garment development was done in two stages which involved creating (1) SMA actuators integrated with soft sensing, and (2) integrating pneumatic actuation. The final soft exoskeleton design was developed based on the insights gained from two prior prototypes in terms of wearability, usability, comfort, and functional specifications (i.e., placement and number) of the sensors and actuators. The final exoskeleton is a modular, multilayer garment which uses a hybrid and customizable actuation strategy (SMA and inflatable pneumatic bladder).
This paper investigates the tradeoffs between design variables important for the development of a mobility support soft exoskeleton for horizontal shoulder adduction. The soft exoskeleton utilizes discreet shape memory alloy (SMA) spring actuators to generate the required torque to move the arm segment, while preserving the qualities of a soft, wearable garment solution. A pilot benchtop test involving varying power input, actuator anchor position, actuator orientation, and added weight, was investigated to evaluate their effects against the degree of motion the soft exoskeleton allows. The results show that the power input, actuator anchor position, and simulated limb weight each affect the ultimate horizontal adduction angle the exoskeleton is able to induce. Further, the project highlights a crucial point in regard to the tradeoffs between functionality and wearability: when actuator orientation was investigated, we found a decrement in functionality (as measured by maximum achievable horizontal adduction angle) when the actuators were constrained close to the body. This shows that when aiming to improve the hypothetical system’s wearability/usability, the effective torque that can be generated is reduced. Together these findings demonstrate important design considerations while developing a wearable, soft exoskeleton system that is capable of effectively supporting movement of the body while maintaining the comfort and discreetness of a regular garment.
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