Advancing Mobile Neuroscience: A Novel Wearable Backpack for Multi-Sensor Research in Urban Environments

The rapid global urbanisation has intensified the need to understand the complex interactions and impacts that city environments have on human physical or mental health and well-being. Traditional indoor laboratory-based approaches conduct experiments in well controlled settings but, while advantageous for their controlled conditions, they often lack ecological validity. To address this gap, we present the "eMOTIONAL Cities Walker Backpack" -- a wearable unit developed for synchronously collecting multi-modal data in dynamic real-world settings. Designed for both indoor and outdoor use, the backpack integrates environmental (for microclimate, air pollution and noise) and physiological sensors (including electroencephalography, eye-tracking and wrist-based biosensors for cardiovascular monitoring) to enable the study of human experience in naturalistic urban environments. In this paper, we describe the technical specifications and implementation of this technology during outdoor acquisitions across selected urban locations in the city of Lisbon. We also highlight its potential for methodological comparison with traditional lab-based tasks (particularly through the use of equivalent sensing technologies), and thus advancing the field of translational research in mental health and urban studies.