Dynamic Facial Prosthetics for Sufferers of Facial Paralysis

Background This paper discusses the various methods and the materials for the fabrication of active artificial facial muscles. The primary use for these will be the reanimation of paralysed or atrophied muscles in sufferers of non-recoverable unilateral facial paralysis. Method The prosthetic solution described in this paper is based on sensing muscle motion of the contralateral healthy muscles and replicating that motion across a patient's paralysed side of the face, via solid state and thin film actuators. The development of this facial prosthetic device focused on recreating a varying intensity smile, with emphasis on timing, displacement and the appearance of the wrinkles and folds that commonly appear around the nose and eyes during the expression. An animatronic face was constructed with actuations being made to a silicone representation musculature, using multiple shape-memory alloy cascades. Alongside the artificial muscle physical prototype, a facial expression recognition software system was constructed. This forms the basis of an automated calibration and reconfiguration system for the artificial muscles following implantation, so as to suit the implantee's unique physiognomy. Results An animatronic model face with silicone musculature was designed and built to evaluate the performance of Shape Memory Alloy artificial muscles, their power control circuitry and software control systems. A dual facial motion sensing system was designed to allow real time control over model -a piezoresistive flex sensor to measure physical motion, and a computer vision system to evaluate real to artificial muscle performance. Analysis of various facial expressions in real subjects was made, which give useful data upon which to base the systems parameter limits. Conclusion The system performed well, and the various strengths and shortcomings of the materials and methods are reviewed and considered for the next research phase, when new polymer based artificial muscles are constructed and evaluated.