This paper presents the work conducted towards the realization of a novel tactile display system composed of miniature thermo-fluidic actuators. An application of the system particularly relevant to blind individuals is communication with computers through touch. The development of programmable spatio-temporal pattern of touch actuation based on bubble formation and vapor pressure has remarkable scope, not only because of the flexibility and wearability but also the high levels of motion amplitude and force of actuation not achieved so far by other means. The design specifications of the tactile display involved packaging of the miniature actuators in such a manner that the display can be conveniently attached at the tip of the human finger with desirable spatial resolution, and achieving the optimum force that can be felt through the human finger. However, there were challenges that were faced by the authors while miniaturizing the actuators for suitability in sub-millimeter spatial resolution desirable for the tactile display. The paper reports on the design, prototype development and experimental results and brings out the limitations along with possible solutions being pursued by the authors. The progressive efforts through fabrication and testing of different prototype thermo-fluidic actuators ranging from 3mm diameter bore to sub-millimeter sizes and the corresponding difficulties faced in the form of cooling requirements, hysteresis effects, and fabrication challenges are elucidated. The paper reports on packaging of actuators as an array of tiny tubes spaced as close as possible, and establishment of parameters, namely, amplitude of actuation and switching frequency, along with force generation adequate for tactile perception.
