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Exosuits typically provide limited mechanical support and rely on a user's residual functional ability. However, people with neurological impairments often suffer from both motor and sensory deficits that limit the assistance an exosuit can provide. To overcome these limitations, we developed the REINFORCE system, that complements the mechanical assistance provided by an exosuit, the Myosuit, with (1) functional electrical stimulation to enhance the activities of leg muscles, and (2) transcutaneous electrical nerve stimulation to restore somatosensory information. It consists of a fully portable and highly modular system that can be easily adapted to the level of impairment and specific need of each participant. Technical verification with three healthy participants showed reliable synchronization between all modules of the systems in all phases of walking. Additionally, we tested the system's effectiveness in one participant with multiple sclerosis who walked overground with and without functional electrical stimulation. Results showed a slight increase in self-selected walking speed (approx. 18%) and in the peak hip flexion at late swing (approx. 12%) as well as reduced step-to-step variability of step length and step time when electrical stimulation was provided. Our findings push towards a clinical trial involving more patients to validate the effectiveness of the REINFORCE system on participants' mobility.

Soft wearable robots to assist human movements, such as exosuits, have rapidly gained attention thanks to their compliance, low weight and accessibility. However, force measurement in exosuits still rely on load cells and rigid sensors that are not wearable or unsuitable for applications outside the lab. Soft, stretchable and lightweight sensors that become invisible when integrated in an exosuit and perfectly conform to the human body represent a promising alternative. In this work, we developed a wearable sensing system based on a soft stretchable silicone-based strain gauge to measure the forces acting in the passive elastic elements of an exosuit. To measure sensor's accuracy, two unimpaired participants walked on a treadmill at speeds between 0.9 and 2.1 $\text{m}\text{s}^{-1}$. When comparing our solution to a state-of-the-art motion capture system, we found an average root mean square error in force estimation of 12.5% and a standard deviation of 7.4%. Furthermore, we showed the portability of our sensory system by monitoring the forces exerted by the wearable robot during outdoor walking. Our study shows the potential of using stretchable sensors to monitor walking patterns in studies outside the lab and to control human-robot interaction.

Objective . Lower limb amputees suffer from a variety of functional deficits related to the absence of sensory communication between the central nervous system and the lost extremity. Indeed, they experience high risk of falls, asymmetric walking and balance, and low prosthesis embodiment, that significantly decrease their quality of life. Presently, there are no commercially available devices able to provide sensory feedback to leg amputees but recently some invasive solutions (i.e. requiring surgery) have been proposed by different research groups. However, a non-invasive effective alternative exploitable in everyday life is still missing. Approach . To address this need we developed and tested a lightweight, non-invasive, wearable technology (NeuroLegs) providing sensory (i.e. knee angle joint and tactile) feedback to the users through electro-cutaneous stimulation. Standard mechanical and electrical tests were performed to assess the safety and reliability of the technology. The NeuroLegs system was verified in terms of accuracy in measuring relevant gait parameters in healthy participants. The effectiveness of the NeuroLegs system at improving walking of three transfemoral amputees was then verified in movement laboratory tests. Main results . No mechanical failures, stable communication among system's parts and a long-lasting battery were demonstrated. A high temporal reliability was found when detecting stride features (important for the real-time configuration) with a correct match to the walking cadence in all assessed walking conditions. Finally, transfemoral amputees showed increased temporal gait symmetry and augmented confidence when walking with the sensory feedback compared to no feedback condition. Stepping outside from the lab, NeuroLegs was successfully exploited by a transfemoral amputee in CYBATHLON Global Edition 2020 in several challenging situations related to daily-living activities. Significance . Our results demonstrate that the NeuroLegs system provides the user with useful sensory information that can be successfully exploited in different walking conditions of daily life., (Creative Commons Attribution license.)