Non-Invasive Stable Sensory Feedback for Closed-Loop Control of Hand Prosthesis

Area of Science:

• Biomedical Engineering
• Neuroscience
• Rehabilitation Engineering

Background:

• Conventional prosthetic hands lack somatotopic sensory feedback, limiting their functional use.
• Restoring sensory feedback is crucial for improving the dexterity and usability of upper-limb prostheses.

Purpose of the Study:

• To integrate a non-invasive sensory feedback system with a commercial prosthetic hand.
• To convey multi-modal sensory information (tactile, hand aperture) to amputees.
• To assess the stability and efficacy of the sensory feedback system.

Main Methods:

• Customized surface stimulation electrodes were designed for evoked tactile sensation (ETS) at projected finger map (PFM) areas.
• An anti-stimulus artifact module filtered surface electromyographic (sEMG) signals for prosthetic hand control.
• The system delivered tactile and hand aperture information via electrotactile stimulation.
• Electrode impedance, perceptual thresholds, and object identification accuracy were evaluated.

Main Results:

• The customized electrodes demonstrated stable alternating-current (AC) impedance over 12 hours.
• Perceptual and upper thresholds remained stable over 200 days, indicating a stable neural interface.
• A forearm amputee achieved 100% accuracy in identifying object compliance and length using the feedback system.

Conclusions:

• The developed non-invasive sensory feedback system provides stable and sufficient information for prosthetic hand users.
• This technology offers a promising approach to restore sensory feedback non-invasively for commercial prosthetic hands.
• The system significantly enhances the ability to discriminate physical features of grasped objects.