Tactile display using shape memory alloy micro-coil actuator and magnetic latch mechanism

•The tactile pins are actuated by an SMA coil actuator and latched by magnetic force.•The pins remain in place even if the electrical current to the SMA actuator is cut off by the latch mechanism.•The 100-pin tactile display consists of 10 stacked modules and latch parts.•The magnetic latch mechanism can control the stroke of the pin accurately without any feedback control.•The magnetic latch mechanism realizes lower electrical consumption and high density of the tactile pins.

A two-dimensional tactile display for visually impaired people was fabricated and successfully operated. Character and graphic information is dynamically displayed by an array of pins in up and down positions. The contraction of shape memory alloy (SMA) micro-coil actuators moves the pins up and down when the SMA actuator is heated by an electrical current. A tube fabricated from magnetic material is attached to each pin and a permanent magnet accurately positions the pins in an up or down state without any feedback control. This latch mechanism overcomes problems of heat storage and electrical consumption of the SMA actuator because the current is supplied only when the pins move. The tactile display has a 100 (10 × 10) pins array. The tactile information is displayed sequentially every 0.3 s and the tactile pins are latched at 0.1 N by magnetic force. The pins are arranged at a pin interval of 2.5 mm and move 2 mm up and down. Furthermore, in order to offer tactile graphic information, the interval between pins is narrow. A module for the tactile display with pin intervals of 1.27 mm has also been developed.