Dilating Pupil for Prosthetic Eyes Based on Electrowetting

Abstract

The prosthetic eye is created to help people who have lost an eye. The eye itself can only improve the appearance but without any optic function. In order to optimize the appearance, a prosthetic eye with a pupil that can dilate and contract according to the light level, just like the natural eye, is desired. The primary goal of this work is to develop and characterize a dilating pupil based on electrowetting. A droplet of an aqueous solution acts as a pupil.
Electrowetting-on-dielectric (EWOD) has become one of the most popular tools in variety of applications, from microfluidics to electrowetting displays. This thesis presents the design of a low-voltage electrowetting one-pixel display which can act as a pupil. Decreasing the maximum actuation voltage is the main objective and challenge of this project. Different methods to achieve this goal are presented in the thesis, including using dielectric materials with better dielectric properties and using electrowetting liquids with lower surface tension. Ways to minimize the effect of gravity are also investigated. Droplet-based simulations are introduced by two methods. The simulation results are used to sustain the design process and for comparison with the measurement results on the real devices. According to the theoretical background and simulations, a test device is designed and fabricated in the cleanroom of EKL, TU Delft. The fabrication details are described in this thesis. Finally, measurements on the fabricated device are performed under different conditions. The results are shown and discussed in the final conclusions. In general it can be said that an electronic dilating pupil based on EWOD seems possible. Some recommendations for the future improvement are made.