A Comparison between Separated Electrodes and Concentric Electrodes for Electrotactile Stimulation

Equipping prosthetic devices with sensory feedback capability is a continuing research challenge to increase their control and embodiment, and to decrease their rejection by their users. Electrotactile stimulation is one of the non-invasive sensory feedback techniques with a low power, light-weight and relatively easy to control stimulation mechanism to provide the feedback. Currently, there are two electrode setups used in the literature, concentric electrodes and separated electrodes, to apply the electrotactile stimulation to deliver tactile feedback. There is minimal data available in the literature to compare the two electrode setups. This study compares the impact of the electrode arrangements on the dynamic range, just noticeable difference (JND), comfort level, degree of localisation, intensity and type of sensation induced, and the resulting EMG interference from the electrotactile stimulation. The experimental results presented suggest that the concentric electrodes induce a more comfortable and realistic sensation with a reduction in the probability of inducing undesired feeling of pain, pinch or pinprick sensations. Further, the concentric electrodes result in an increased localisation of the induced sensation whilst maintaining a similar dynamic range and JND. EMG interference was shown to be lower for the concentric electrodes.