The design of pressure-controlled valves for a refreshable tactile display

In this paper, we explore key design parameters for integrating fluidic logic and actuators for a very-large shape display for application in braille and tactile graphics. We present a simple model of pressure-controlled flow valves, which are analogous to electric transistors. The model is used to highlight the design of a valve that achieves hysteresis (noise immunity) and pressure-gain (signal propagation), both critical goals for creating fluidic logic circuits. Empirical results from a family of valves fabricated with graded design parameters and assembled in a logical NOT gate configuration back up the model. A pressure-gain of up to 26 kPa is achieved for a 80 kPa pressure supply, enabling the output of any logic gate to serve as the input of another in a sequential logic operation. Using the pressure-gain valves, we successfully built a latching memory unit that can be integrated with a pneumatic actuator capable of driving a braille pin. The design is sufficiently scalable and manufacturable to support the realization of a large dense array of pins at braille spacing.