COMPUTATIONAL FEASIBILITY AND DESIGN REQUIREMENTS FOR DEAFBLIND HAPTIC INTERFACES: A SYSTEMATIC REVIEW AND PATENT LANDSCAPE OF SIGN LANGUAGE NOTATION PREPRINT

According to the World Federation of the Deafblind, deafblindness affects approximately 0.2% of the global population in its severe form, potentially reaching 2% when including milder manifestations. Despite this, most assistive technologies focus on speech translation or gestural sign reproduction, leaving tactile literacy in the background. This work aims to validate the scientific and technological gap regarding the tactile implementation of sign language writing and to theoretically compare SignWriting (SW) and ELiS regarding engineering feasibility and perception. The methodological triangulation comprises: (1) A PRISMA-based Systematic Literature Review (SLR) across 5 indexed databases; (2) A Patent Landscape in 5 global patent databases; and (3) A comparative theoretical analysis based on 5 Human-Computer Interaction (HCI) and psychophysics criteria. The SLR retrieved 99 records (63 unique), resulting in zero implementations of structured notations for deafblind users. The prospection identified 151 patents but confirmed the absence of filings in this specific combination-a true white space. The theoretical analysis indicates that the ELiS system outperforms SW in the critical criteria of dimensionality and cognitive load. In summary, a validated 'triple gap' is evidenced: scientific, technological, and theoretical. ELiS presents itself as the most viable solution for haptic interfaces within HCI, due to its linearity, lower symbolic complexity (95 vs. 652 symbols), and native compatibility with sequential tactile perception and additive manufacture.