Electrotactile stimulation at the lateral torso to convey messages using spatial patterns

Abstract:The present work introduces preliminary re-sults of an EU H2020 project aiming to develop an un-obtrusive system to assist first responders by conveying additional information through electrotactile feedback. This study assessed three different encoding schemes for delivering tactile messages in form of spatial patterns. Patterns were delivered using simultaneous activation, sequential activation, and sequential activation with fre-quency modulation of pads. Biphasic pulses with a pulse duration of 400 μs and frequency of 25, 50 and 150 Hz were delivered through a surface electrode (2 × 3 matrix array) placed at the lateral torso. The success rate in iden-tification of electrotactile spatial patterns was quantified in healthy subjects. Simultaneous activation resulted in poor performance, improving with the sequential ap-proach. The best results were achieved using mixed en-coding (sequential activation plus frequency modulation) with success rates of approximately 80%. These prelimi-nary results suggest the feasibility of conveying and iden-tifying electrotactile spatial patterns at the lateral torso when the encoding scheme incorporates spatiotemporal stimulation profiles, rather than simultaneous electrode activation. These are encouraging results since reliable recognition of spatial patterns can enable high- bandwidth communication through tactile channels.