Evaluating Distinct Sensations by Modulating High-Frequency Electrotactile Pulses for Unobtrusive Communication with IoT Devices

IoT devices that report information to a user, such as fitness trackers, exhibit a need for user feedback capable of communicating a wide range of messages in an unobtrusive manner. This paper describes the use of high-frequency electrotactile stimulation pulses for producing multiple distinct sensations within a limited messaging window of 0.5s that serve as unobtrusive and discreet feedback messages. Two experiments were conducted on willing participants using a custom electrotactile stimulator. Experiment 1 investigated the effectiveness of producing unique sensations by varying a compound electrotactile stimulation where a 1kHz pulse train is modulated by a frequency between 10Hz and 100Hz (mid-range frequencies). Results indicate that participants can discriminate midrange frequencies utilizing compound electrotactile stimulus composed of 1kHz pulses. Experiment 2 investigated the effectiveness of creating new sensations by modulating high-frequency pulse trains with a mid-range "Bundle" frequency of varying duty cycle. Results show that variations in Bundle frequency duty-cycle produced at least three distinct sensations that may be employed to produce distinct sensations. Such distinct electrotactile sensations permit unobtrusive communication between individuals and wearable IoT device.