Frequency shaping of tactile perception via transcutaneous interferential electrical stimulation: a simulation study

Electrotactile feedback via transcutaneous interferential electrical stimulation generates temporally modulated stimulation fields and enables frequency-domain adjustment with carrier and beat frequencies. To systematically characterize these effects, we present a simulation framework that integrates tissue-scale electrical potential simulation with the finite element method and axon-scale dynamics using the axon cable equation, which incorporates cable theory and the Hodgkin-Huxley model, to predict axon activation and tactile perceptual metrics. We simulated a simplified glabrous skin model with three orthogonally oriented axons. Results show that the carrier frequency in the range of 1-4 kHz determines the upper bounds of the perceived field size, reaching up to 1.6 mm and exceeding the 1 mm electrode diameter, and perceived intensity, whereas the beat frequency in the range of 0-100 Hz adjusts these quantities within these bounds. Furthermore, axons oriented perpendicular to the skin surface exhibit lower activation thresholds than those oriented parallel. Unlike the conventional approaches of transcutaneous electrical stimulation, our results suggest that transcutaneous interferential electrical stimulation can shape the perceived field and perceived intensity without electrode reconfiguration or amplitude modulation. These findings clarify the distinct roles of carrier and beat frequency in tactile perception. This paper provides a theoretical foundation for frequency-domain adjustment of electrotactile interfaces and points toward compact, programmable systems. Quantitative validation through psychophysical experiments will further test and refine these predictions.