Surface texture and pseudo tactile sensation displayed by a MEMS-based tactile display

We demonstrate display of artificial tactile feeling using large displacement MEMS actuator arrays. Each actuator consists of a piezoelectric actuator and hydraulic displacement amplification mechanism (HDAM) that encapsulates incompressible liquid in a micro-chamber with two flexible polymer membranes. In prior work, we experimentally applied the actuator arrays to an efficient vibrational Braille code display. In this paper, we investigated the artificial tactile feeling projected onto the fingertip in contact with the display while the actuation pattern was controlled both temporally and spatially. The arrays could successfully display two relative tactile feelings, 'rough' and 'smooth', distinctly when the vibrational frequency of the individual actuator and switching time of the lines of actuators were controlled. In addition, we found that pseudo tactile sensation appeared between the adjacent cells of the display while the two actuators were controlled to have identical vibrating frequencies. We experimentally deduced the conditions when the pseudo tactile sensation was generated and the 'effective' resolution of the display was augmented. Pseudo tactile sensation would enable the display to transfer more variable tactile sensation and thus, information to the finger.