A thermo-activated tactile micro-actuator for displays

摘要

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 thereto-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(C), 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 (R) 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 (R) drop. These measurements have been achieved by using the Laser Doppler Vibrometer in the "topography mode" and revealed a total displacement of 50 mu m when a tension of 2.4 V is applied at taxel terminals and, according to the Joules law, a power converted from electrical energy to thermal energy of 7,2 W.