Development of medical and welfare instruments using smart materials: Tactile sensor system for reading Braille

Touch is the most frequently used action to gather the information outside the body. In our daily life, various kinds of things are touched by fingers and their physical as well as morphological features are extracted and evaluated unconsciously. Palpation of the finger is often used on the medical field. However, the rate of correct diagnosis is dependent on the doctor's experiences. Furthermore, it is difficult for the function of tactile sensation to disappear and the function enables to substitute another sense, since skin is the biggest organ among human body. The current output from the polyvinylidene fluoride (PVDF) film is proportional to the rate of the strain induced in the film. The time variation is quite similar to the signal variation of the Pacinian corpuscle which is a sensory receptor in the dermis particularly functional to the touch-vibration. These situations have drawn interest in the development of an objective tactile sensor using smart materials for the medical and welfare instruments. Recently, we investigate the development of a tactile sensor for reading Braille. Braille is a language for visually disabled persons, in which characters are represented by patterns of raised dots so that the persons can read by the sense of touch on their fingertip. It uses a combination of six dots, in two parallel lines of three. However, learning Braille requires great efforts. We are concern with the development of a tactile sensor system for reading Braille without special training by just scanning over Braille. The tactile sensor uses a PVDF film as the sensory material. The system is verified whether it has enough performance to recognize a string of letters appropriately. The obtained result shows that the proposed sensor and sensor system are effective to recognize Braille.