Experimental investigation of a display chip incorporating an electrostatic actuating polymer membrane

Abstract

By integrating a planar waveguide and scattering phenomenon generated by electrostatically actuating a transparent polymer thin film, a display chip capable of being cleared and re-displayed was developed using micro fabrication technology. In the design of the display chip, a freestanding transparent PDMS/ITO conductive composite membrane is sustained by SU-8 spacers above a glass substrate which acts as a light waveguide, and electrostatic force is used to carry out the deflection of the PDMS/ITO composite membrane. When electrostatic force is applied, the PDMS/ITO composite membrane deflects and comes into contact with the glass substrate, causing light to leak out of the waveguide, due to which the critical angle of the total internal reflection of the glass waveguide changes. On switching off the electric potential, the PDMS/ITO membrane returns to its initial state so that light cannot leak out, and a dark spot is formed. Thus, micro-optical switching can be performed by this mechanism. In this display chip an aluminum layer was applied as an adhesive layer between the SU-8 spacers and the glass waveguide, which prevented the leakage of light. The experimental results show that a waveguide with an electrode length of 250 µm (sub-pixel length), a micro-post height of 23 µm and a PDMS film thickness of 8 µm require an actuator voltage of 149 V to operate in a pull-in mode. The optical testing results successfully demonstrate the functionality and the ability to light up multiple pixels of an electrostatic actuating display (EAD) device. Therefore, the EAD device has great potential for the development of low cost dual displays.