Feasibility Study of the Flash-Sole: A Wearable Midsole With Soft Actuators for Walking Assistance

This study evaluates the feasibility, usability, and functional performance of the Flash-Sole, a novel wearable robotic midsole developed at the University of Nebraska at Omaha (UNO). The Flash-Sole is powered by stacked dielectric elastomer actuators and designed to provide gentle push-off assistance during walking. This early-stage trial focuses on determining whether the Flash-Sole system can be safely and comfortably worn by healthy adults and whether it functions as intended in a laboratory environment.

The study uses a single-session, within-subject design with up to 15 participants. Each participant will complete walking trials in both baseline conditions (standard shoes) and experimental conditions (Flash-Sole shoes with the system either active or inactive). The research will compare gait parameters and user feedback across these conditions. No control group or randomization is used, as this study is exploratory and not powered to assess clinical outcomes.

During the single session (~2 hours), participants will:

• Complete screening for eligibility
• Perform short walking tasks in standard shoes and Flash-Sole shoes
• Walk on a treadmill at a self-selected comfortable speed
• Wear surface EMG and IMU sensors to measure muscle activity and movement
• Provide subjective feedback via standardized usability questionnaires (e.g., System Usability Scale and QUEST 2.0) The primary outcomes of interest include system functionality (e.g., successful actuator activation), usability (System Usability Scale score), and user-reported comfort and ease of use (QUEST 2.0). Secondary outcomes include basic gait characteristics (e.g., cadence, step length) and participant-reported adverse effects, if any.

All walking trials will be short (approximately one minute per trial), conducted with rest breaks between trials as needed. A fall-prevention safety harness will be worn at all times. No investigational drugs or implanted devices are used. The Flash-Sole system is investigational and not approved by the U.S. FDA. The study is not conducted under an IDE.

Data will be analyzed using descriptive statistics to characterize usability, comfort, and functional performance metrics. Due to the small sample size and feasibility nature of the study, inferential statistics will be limited and exploratory only.

This study is intended to inform future device refinements and guide the development of subsequent clinical trials involving individuals with walking impairments, such as stroke survivors or children with cerebral palsy.

Inclusion criteria

• Age: 19 to 45 years old at the time of consent
• Able to understand study procedures and provide informed consent
• Able to walk independently without assistive devices
• Willing to wear the Flash-Sole device and complete gait trials during a single session
• Body weight under 80 kg to comply with device safety specifications

Exclusion criteria

• Current or recent (within 6 months) lower-limb injury, surgery, or fracture
• History of neurologic, musculoskeletal, or cardiovascular conditions affecting gait
• Skin conditions, open wounds, or known allergies at the foot/ankle that interfere with device wear
• Use of implanted electronic medical devices (e.g., pacemakers, neurostimulators)
• Cognitive or language impairments that preclude informed consent or task participation
• no medication related to musculoskeletal condition (e.g., pain relief medications or similar treatments) .