• Ag/AgCl
• assessment
• EMG
• in-field
• low-profile
• musculoskeletal
• occupational exoskeletons
• temporary tattoo electrodes
• upper-limb exoskeletons
• wearable robotics
• work-related
• workers assistance
• WRMSD

In a wide range of productive facilities across various industrial sectors, numerous tasks cannot be effectively automated, and necessitate human workers to be performed. To maintain high production rates, these often strenuous and repetitive tasks can lead to the development of work-related musculoskeletal disorders (WRMSDs), impacting workers' health and reducing overall business productivity. Occupational exoskeletons can be suggested as a means to prevent WRMSDs and enhance productivity, provided there is satisfactory proof of their effectiveness. This proof should ideally be obtained under realistic conditions with actual workers, in the intended workplace, without disrupting the wearer's tasks to ensure neither the business operations nor the validity of the test are compromised.
The exoskeleton’s effectiveness in allaying physical stress while carrying out work activities can be assessed through the real-time acquisition of the EMG signal of key muscles involved in the assisted actions, since the EMG signal is deemed to be a good estimator of physical effort. The EMG sensors universally recognized as the gold-standard are rigid silver and silver chloride electrodes (Ag/AgCl), which however present significant issues: size, rigid core susceptible to movement, skin slippage, and chattering phenomena negatively affect the reliability of EMG measurement during dynamic tasks. Within the specific exoskeletons application context, their encumbrance effectively prevents proper EMG recording of muscles that fall under the exoskeleton frame and harness: this way, it might be difficult to conduct a comprehensive statistical analysis that effectively demonstrates task relief resulting from device use, rather than a redistribution of effort to other body districts, and it can also be complex to assess possible negative implications involving the said hard-to-reach muscles.
 
The occupational exoskeletons technology has reached a level of maturity which calls for a greater number of in-field studies, where instrumentation for evaluating its effects is more limited and must comply with stricter constraints of size, robustness, usability, and acceptability. It is equally important to introduce an effective methodology to gather information on the effort of all muscles involved in the assisted tasks, so as to obtain valid documentation for possible regulation and commercialization.
This work of thesis analyzes a new type of ultra-low profile EMG sensor, the PEDOT:PSS Temporary Tattoo Electrode (TTE), of which several interesting qualities have been demonstrated, such as great mechanical robustness to movement and resistance to movement artifacts along with better wearability, while maintaining a good SNR ratio, biocompatibility and reduced production costs. The mechanism of complete adherence to the epidermis is deemed to make a significant contribution to their reliability, especially under dynamic conditions, and their breathability allows physiological sweating without loss of functionality.
The precise purpose of this study is to integrate the ultra-low profile TTEs with a semi-active upper-limb occupational exoskeleton to perform EMG measurements intended for the evaluation of the effects of the exoskeleton assistance on specific muscle groups, in order to determine whether the TTEs’ characteristics are maintained when worn in conjunction with an occupational exoskeleton: to do so, a usage methodology, comprising a setup and experimental protocol, has been devised, on the grounds of current knowledge on the exoskeleton assessment procedures but also aiming to a thorough comparison of the EMG signals acquired with standard Ag/AgCl electrodes and the TTEs.