A thermo-activated tactile micro-actuator for displays

Abstract

In this work we report the design, the fabrication and the characterization of an innovative soft tactile micro-actuator, also called TAXEL (TActile piXEL), which is developed to be integrated in a portable tactile display for providing text content and graphical information to visually impaired people through the sense of touch. It exploits a thermo-active approach, by taking inspiration from common thermometers: the actuator is activated by the thermal deformation of an active material, namely the metallic alloy Galinstan©, determined by heating the alloy through an underlying metallic resistor designed to work as a heater. The microfabrication of TAXELs is achieved in several steps consisting in heater fabrication, in SU8 micro chambers fabrication, in the deposition of Galinstan® inside and sealing by a PDMS membrane. Measurements of the TAXEL deformation have been accomplished by measuring the displacement of the PDMS sealing membrane, which is promoted by the expansion of the heated Galinstan® drop. These measurements have been achieved by using the Laser Doppler Vibrometer in the “topography mode “and revealed a total displacement of 50 μm when a tension of 2.4 V is applied at taxel terminals and, according to the Joule's law, a power converted from electrical energy to thermal energy of 7,2 W.