NRI: Towards Restoring Natural Sensation of Hand Amputees via Wearable Surface Grid Electrodes

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Hand amputation can severely limit the quality of life, for example by making it impossible to sense and manipulate objects, or to express gestures. Many robotic prosthetic hands have been developed to date, some of which have dexterity approaching that of a human hand, but a key factor limiting acceptance of these devices is the lack of natural and reliable sensory feedback to the user; the substitution of un-natural stimuli such as skin vibration, visual or audio cues doesn't really cut it. The PI's goal in this research is to explore the use of non-invasive grid electrodes for electrically stimulating the peripheral sensory nerves so they transmit natural (high resolution) haptic sensations to the central nervous system. Success of this project will revolutionize the way in which human beings communicate with robotic prostheses and transform research in close-loop prosthesis control, shifting amputee haptic sensation feedback from invasive implant techniques to non-invasive surface probing techniques. The non-invasive nature of the new technology presents the potential for rapid clinical translations with high functional efficiency and user acceptance. Thus, the research will lead to dramatic improvements in hand amputees' quality of life. In addition, the work will be integrated into graduate and undergraduate student education at the PI's institution, and outreach programs for K-12 students (especially underrepresented STEM students) will expose them to this innovative science.This highly creative project adopts an approach that is completely different from the existing techniques for providing sensory restoration/augmentation, and which is supported by the team's preliminary studies. First, the investigators will design a novel, non-invasive nanowire sensor array that will provide natural sensation of the missing hand. The thin-film electrode grid will be self-adhesive and highly stretchable. The multifunctional electrodes will be able not only to provide targeted nerve stimulation but also to record pressures applied on the prosthetic hand, so they can both obtain a rich set of haptic information and also deliver this information to the user accurately and precisely, while inducing minimal interference such as skin discomfort, added weight due to the device, and control signal interference. Second, the team will create a new way of affording sensory restoration by developing a dynamic stimulation scheme that encodes spatially distinct haptic sensations in the digits and palm. This will be achieved by selectively recruiting the various afferent fibers innervating different regions of the hand. The investigators believe that with high spatial resolution based on hand region mapping, the haptic feedback could for the first time enable users to truly perceive the environment by "using" their lost hand, and thereby push the sense of embodiment to a new level. Lastly, new knowledge will be obtained by quantifying the effect of the sensorimotor integration process on closed-loop control of a dexterous prosthetic hand in amputees.