Research ArticlesBioengineering

Restoring Natural Sensory Feedback in Real-Time Bidirectional Hand Prostheses

Science Translational Medicine  05 Feb 2014:
Vol. 6, Issue 222, pp. 222ra19
DOI: 10.1126/scitranslmed.3006820

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An Artificial Hand’s Sense of Touch

To feel the hard curvature of a baseball or the soft cylinder that is a soda can—these sensations we often take for granted. But amputees with a prosthetic arm know only that they are holding an object, the shape and stiffness discernible only by eye or from experience. Toward a more sophisticated prosthetic that can “feel” an object, Raspopovic and colleagues incorporated a feedback system connected to the amputee’s arm nerves, which delivers sensory information in real time. The authors connected electrodes in the arm nerves to sensors in two fingers of the prosthetic hand. To “feel” an object, the electrodes delivered electrical stimuli to the nerves that were proportional to the finger sensor readouts. To grasp an object and perform other motor commands, muscle signals were decoded. This bidirectional hand prosthetic was tested in a single amputee who was blindfolded and acoustically shielded to assure that sound and vision were not being used to manipulate objects. In more than 700 trials, the subject showed that he could modulate force and grasp and identify physical characteristics of different types of objects, such as cotton balls, an orange, and a piece of wood. Such sensory feedback with precise control over a hand prosthetic would allow amputees to more freely and naturally explore their environments.