Proposal of a Novel Neuromorphic Optical Tactile Sensor for Applications in Prosthetic Hands

The development of highly sophisticated prosthetic hands is a long-sought goal for biomedical engineers. Overall improvements in hand design and control via myoelectric signals (EMG) allowed the development of devices with more degrees of freedom and higher capabilities. While the motor aspects of prosthetic hands have greatly evolved, there is room for improvements in their sensory aspects. Incorporating tactile sensors into the robotic fingers should improve the overall control of the hand, providing more safety when manipulating objects. Despite the many tactile sensors presented in the literature, there is a need for more flexible and higher-density tactile sensors. In this paper, we present the design of a novel neuromorphic tactile sensor for prosthetic hands. The sensor is composed by a photodiode array and light-emitting diodes (LEDs) embedded into a soft elastomer material. Forces applied to this artificial skin causes deformation of the elastomer, changing the distribution of light over the photodiodes, generating the tactile signal. We also follow a neuromorphic approach by converting such signals into spikes that mimic the behavior of Merkel Cells present in the glabrous skin. These mechanoreceptors are slow-adapting and encode static forces applied over the skin. The proposed tactile sensor is promising and can be incorporated to prosthetic hands to improve their dexterity in a biomimetic manner.