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Member of: Theses and Dissertations

Evaluating the Impact of a Back-Support Device on Human Stability During Trip Perturbations

Description

This study aimed to evaluate the effectiveness of a novel wearable back-support device in enhancing postural stability among healthy individuals subjected to unexpected perturbations, simulating scenarios relevant to fall prevention. Specifically, the device was assessed under two experimental conditions: Standing with Perturbations (SWP) and Walking with Perturbations (WWP). Participants underwent trials across three distinct device stiffness levels. The primary outcome measure was the Margin of Stability (MOS), quantifying subjects’ balance control at the instant of maximal instability following perturbations. Results indicated a positive trend of increased MOS values with higher stiffness levels, suggesting enhanced stability support provided by the device. Statistical analysis revealed that the device significantly improved postural stability under the highest stiffness level. However, considerable variance was observed across participants’ results, likely due to substantial inter-subject variability in neuromechanical control strategies. Individualized analyses highlighted the importance of considering subject-specific responses when evaluating assistive device efficacy. This study underscores the potential benefit of adjustable stiffness in wearable devices to enhance human stability during perturbations. Future studies should explore individualized stiffness optimization and extend investigations to elderly populations or individuals with increased fall risks.

ContributorsChen, Yuanhao (Author) / Lee, Hyunglae (Thesis advisor) / Berman, Spring (Committee member) / Sun, Jiefeng (Committee member) / Arizona State University (Publisher)

Created2025

Biomechanical Evaluation of a Soft Back Exosuit on Human Stability During Perturbed Walking

Description

This project investigated how a wearable device with adjustable stiffness affects balance recovery during walking perturbations. Using a controlled experimental setup, we analyzed how subjects responded to trip-like disturbances with the device set to different stiffness levels. The Margin of Stability (MOS) was used as the key outcome measure to assess dynamic balance. Results showed that increased device stiffness generally led to improved stability, though individual responses varied due to differences in body mechanics and neuromuscular strategies. These findings highlight the potential for personalized calibration in balance assistive technologies and rehabilitation interventions.

ContributorsWilliamson, Cory (Author) / Lee, Hyunglae (Thesis director) / Sun, Jiefeng (Committee member) / Barrett, The Honors College (Contributor) / Harrington Bioengineering Program (Contributor) / School of Biological & Health Systems Engineering (Contributor)

Created2025-05

Liquid Metal-Based Strain Sensor with Improved Robustness and Sensitivity

Description

This research heavily involves improving the fabrication process of liquid metal soft strain (LMSS) sensors, which improves the robustness and sensitivity of the sensors. Traditional LMSS sensors can experience channel collapse as microchannels deform and lose conductivity under higher elongation when created manually without the use of advanced equipment. To address this issue, pressurizing the liquid metal (LM) was initially proposed as a solution after liquid metal sensors fabricated manually were characterized. After iterating the fabrication method with the use of a spin coater and a resin printer, the most recent sensors that were created during this project were able to not only withstand strains up to 800% but also increase the minimum aspect ratio of channel dimensions. The final sensor designs were fabricated using Ecoflex 00-10 silicone filled with Eutectic Gallium-Indium (EGaIn). This specific type of liquid metal was chosen because of its low toxicity, high conductivity, and liquid state at room temperature. The smallest microchannel dimensions at which the sensors were fabricated at were (WxH) 0.4 mm x 0.2 mm, 0.3 mm x 0.15 mm, and 0.2 mm x 0.1 mm channels. Small aspect ratios were considered to maximize sensitivity and improve resolution. The robustness of the sensor was achievable through different fabricating methods, the main differences being manual vs spin coating techniques. This was confirmed through tensile testing, where the sensors demonstrated improved reliability and consistent conductivity at higher strains compared to the sensors that were created without the spin coater. Shrinking the dimensions and the channel size not only provide a more sensitive sensor that is useful for measurement, but it can also open opportunities in human assisting technology where enhanced LMSS sensors have potential applications in biomechanical monitoring, such as human joint angle measurement and wearable motion tracking.

ContributorsFurukawa, Cindy (Author) / Sun, Jiefeng (Thesis director) / Lee, Hyunglae (Committee member) / Barrett, The Honors College (Contributor) / Mechanical and Aerospace Engineering Program (Contributor)

Created2025-05