Use of High-Frequency Pulses to Generate Unique Electrotactile Sensations for Real-Time Feedback in Wearable Sensory Systems

Wearable real-time systems such as health monitors exhibit a need for user feedback capable of communicating a wide range of messages. This paper describes how high-frequency (100 − 2k Hz) electrotactile stimulation pulses can be utilized for producing multiple unique message sensations within a limited time period of 0.5s. Two experiments were conducted on willing participants using a custom electrotactile stimulator. Experiment 1 investigated the effectiveness of producing unique sensations by varying electrotactile pulse frequency above 100Hz. Results indicate that even though pulse frequencies above 100Hz produce detectable sensations, discrimination by frequency higher than 100Hz is not feasible. Experiment 2 investigated the effectiveness of discriminating electrotactile pulse frequencies higher than 100Hz when the signal was modulated at a fixed low frequency (6Hz) “bundle”. Results show that variations in low-frequency Bundle duty-cycle produced at least three distinct sensations that may be utilized to expand the available set of uniquely perceived electrotactile sensations.