Multipoint electrotactile fingertip stimulation for grasping force feedback in virtual reality

Abstract

Immersive virtual reality systems often lack realistic tactile feedback, preventing the closure of the sensorimotor loop that is essential for fine and dexterous object manipulation. In this study, we compared different encoding strategies for delivering multipoint electrotactile feedback at the fingertips during virtual hand–object interaction. A wearable interface embedding a 2 × 3 matrix of pads on each fingertip was used to provide grasp force feedback during a force-control pick-and-place task within a virtual environment. The grasp force was discretized into six levels and conveyed using three encoding schemes: temporal modulation via stimulation frequency, spatial modulation via the number of active pads, and a mixed approach combining both. Twelve participants performed the task under each feedback condition to evaluate which encoding strategy was the most effective. The results demonstrated the beneficial effects of electrotactile feedback compared to no feedback as reflected by increased accuracy and reduced deviation from the target force, yet at the expense of increased task completion time. Among the encoding strategies, the mixed and spatial modulation outperformed the frequency encoding, and the mixed scheme yielded the best overall performance and user experience, suggesting that integrating spatial and temporal cues enhances the perceptual resolution of electrotactile feedback. Overall, these findings show that the design of the encoding strategy strongly influences feedback effectiveness, demonstrating the potential of wearable electrotactile interfaces to augment VR performance and overall user experience.