Reduction of electrotactile perception threshold using subthreshold vibrotactile stimuli

Electrotactile Perception Threshold (EPT) is critical for designing electrotactile displays, which is the minimum amplitude of an electrical stimulus that can be perceived. A significant concern in electrotactile displays is skin irritation and burns due to prolonged electrical stimulus with high amplitude. This study aims to propose a method for reducing the EPT using a background stimulation with a vibrotactile display at subthreshold: 90% of the Vibration Perception Threshold (VPT) at 235 Hz. A psychophysical experiment was conducted to measure EPT at the middle of the left forearm with and without the vibrotactile display using the staircase method. A reduction of 3 to 5% in EPT was observed, which can be further enhanced with varying study parameters. In addition, the comfort and safety aspects of the user's assessment have been analyzed. Electrotactile stimulations have a higher Steven's power exponent (1.51). Hence a reduced threshold (although it's only 3 to 5%) would be perceptually significant and advantageous for sensory substitution and rehabilitation (vision, auditory, and gustatory).