Development of sensory feedback systems: devices and strategies

Advancements in neuroscience and robotics have opened up new possibilities for developing innovative neural prostheses for limb replacement. To ensure the success of such prostheses, it is crucial to establish a stable and reliable connection between the artificial limb, residual muscles, and the nervous system. Communication with the nervous system can be established using invasive or non-invasive techniques. However, to restore the natural sense of touch, prosthetic devices and stimulating strategies must be capable of imitating the natural pattern activation of skin receptors. Human skin is composed of different receptors, and the natural sense of touch results from the synergistic activation of these receptors. Restoring the natural sense of touch requires respecting the natural pattern activation of skin receptors. However, the ability to restore the sense of touch in bionic prostheses is limited by three technological aspects: the interface with the nerves, the kind of electrode employed, and the nerve stimulation performed. To address these limitations, this thesis investigated the capability of stimulating nerves with novel paradigms. New stimulation strategies were tested with the collaboration of eleven able-bodied volunteers. Four non-rectangular waveforms were implemented and compared to the classic rectangular waveform. The results showed that the neurostimulation profile can influence neural fiber recruitment and induced sensation. The development of devices for sensory feedback was carried out from two different points of view. First, a non-invasive, low-cost, wearable, high-voltage compliant current stimulator for non-invasive sensory feedback was developed using Components-Off-The-Shelf (COTS). The device was tested on a volunteer and could stimulate the hand’s nerves correctly. Second, an invasive, fully implantable bidirectional wireless interface for neurostimulation and prosthetic control was developed. The interface includes a tuning circuit that automatically maximizes the power an implanted unit receives, even in parameter variations.